Off axis guiding doesn't need to be complicated! If you use an SCT or have a lot of available backfocus, I highly recommend the excellent Celestron OAG paired with a large-sensor guide camera: Celestron OAG: bit.ly/44yqc9a Large sensor guide camera: bit.ly/3P2Ps1s ZWO OAG base: bit.ly/3qTetnY ZWO Helical Focuser: bit.ly/44u8weT Or High Point Scientific: bit.ly/3sEf39t Support me on Patreon!: www.patreon.com/cuivlazygeek If you're planning on buying equipment (or anything from Amazon), it will help me if you first click the affiliate links in the description!
Saturn in opposition and Jupiter in opposition soon. Any chance of planet capturing comparing different camera manufacturers? Asiair planet capturing and stacking? Also heard about a comet filter. Do they work?
I just started using OAG with my new FRA600. I am getting the best guiding I have ever had. Where I was getting 50 t0 100 RMS. I am now getting 20 to 50 RMS. I wish I had not let my worries get the best of me and prevent me from using OAG.
@@CuivTheLazyGeek As for focus. I'm using an asi120mm mini. I took the black extension off and I was able to get focus. I'm using the Askar OAG with the helical focuser.
Happy to hear the OAG solved the problem! That’s great news! Every time I watch one of your videos I learn something new. I never dreamed of checking the imaging sensor position relative to the OAG prism. Will do that! Thanks, Cuiv!
So, your best system was Vixen. You are like magnet trying to move in this direction. I glad you came to conclusion that CEM60, fastar, non-edge SCt are good, but “good” is not good enough.
What a coincidence. I just had the exactly same issue. Since I usually only expose for 150-180s at a time, I never noticed it, but when I got the DuoNarrowband, I wanted to push for 5-10 Minute exposures. And I also had completely unusable images, despite very good tracking. I am using a 8" Newtonian telescope with a 180mm guidescope. People told me it has to be flexure, so I bought a new dovetail, which allowed me to actually screw it on the telescope rings. But even then, I still had the same issue. A lot of testing and eliminating other issues later, I was just hit with frustration. I then bought an OAG as a last resort, which sadly doesn't allow me to use a manual rotator anymore due to distance issues, but still I would never want to miss it anymore. Sure, it was a little finicky to set up, but the first image I took filled me with pure joy. A 15 minute exposure, with actually quite bad guiding (prob due to bad seeing) in comparison, and still I had perfect stars. Would never want to miss it again!
Cuiv. The black ring at the bottom of the helical focuser is a 10mm T2 spacer. You can remove it (or add a thinner one) to make the focuser shorter (or longer with a thicker one). The ring is very tightly screwed on but can be taken off. I had the same problem until I realised this.
Thats where I'm at. In 5th grade i bought my first telescope. A 4.5 inch orion short tube on an non mortorized eq mount. I never learned how to even polar align. I always star gazed but fell away from the hobby a bit. Ive had my seestar now ( which looking for videos helped me find your channel) i love it so much and I'm hooked again. Now I'm already putting together a shopping list of astrophotography parts. I want more clearity. More power. Control of what field of view i can have. And sharp sharp details. I'm thinking since I'm new i will probably get locked into the zwo-verse. But watching your videos and seeing you over come and learn things and sharing your knowledge is a god send. Lol anyway thays my pointless story. But i think this is many of us. Keep up the content :)
@CuivTheLazyGeek thank you man. This is why community is great. Your passion helps us pursue ours and our positive feedback can help you. I watch my friend start a RUclips page. He has since stopped it because editing videos was just too much. So I understand it's not easy to stay at it sometimes. But trust me we all hope you will. Clear skies brother.
Your explanations are always so detailed and easy to follow and fascinating even though this is way more advanced than my star adventurer and recently acquired Vespera. Thank you!
Take a look at askar OAG it is so much more robust and well made! Another thing is that Askar prism is 10x10 and zwo is 8x8. I have both and my guide precision sky rocket. Be sure you have low-bortle skies or a modern high QE mono cam. Saw a lot of folks having problems with a lack of guide stars due to low light even with 3s phd intervals.
Thank you for that explanation Cuiv! My rig is an old Alt-Az Celestron NexStar 127SLT (1500mm, 5 inch Cassegrain), which doesn’t have an ST4 compatible port for guiding, but it has something in common with your rig, which lead me realise what was happening to yours. It’s the longer focal length than previously used small rigs. The greater it is, the more everything will need to be accurate in your rig. Every single thing that deviates, will be greatly exaggerated when the focal length increases. I’m using mine mostly for planetary imaging, and to do so, I was also using a 5x TeleVue PowerMate. This would increase the focal length to the extremes for the lousy mount that I have, which by the way doesn’t even have a clutch to balance it, so I’ve been doing the balancing off mount before mounting the scope to it, and marking approximately how far I should move the dovetai. Anyway, when I was trying to focus manually, this absurd focal length, would make it impossible, because I also had the image at 10x on the back of my Canon DSLR, and a planet would disappear from view even with the slightest touch. I’ve since made a DIY focuser with a tiny stepper motor and an Arduino driving it, and I’ve resolved that, but what you were dealing with, brought back in memory all those issues I had to overcome, to (partially) fix the ones my rig had.
Glad to here the use of the OAG sorted out the guiding issues. They can be a bit of trouble to get setup initally but once working, they are great, especially for long focal lengths. I am using OAG's for my two bigger rigs, the Meade 10" SCT and my SkyWatcher Esprit 120 (probably not necessary for the Esprit but guiding is great and I can get up to 20min exposures on both rigs). I used to use the the smaller OAG from ZWO (looks like the one you have) but I found it was too easy to slightly push the camera off center because the OAG uses those three screws for attaching into the imaging train and it's not that easy to get them exactly even and therefore exactly straight. In the end I swapped it out for the OAG-L (now using them on both rigs) as I could bolt them to the filter wheels on the "camera" side and on the telescope side it's a screw together connector so I know everything is as straight as possible.
I'm so glad to see more experienced astrophotographers loving the 150P. I bought it last year (after SO MUCH research and back and forth) as my very first imaging scope and it's been performing amazing for me. It's nice to know my decision was sound and it's even better having people like you to now show me what I can do to make this little scope even better!
I’m graduating from a 90mm refractor with guide scope to a 200mm f4 Newtonian and just purchased a ZWO OAG. Going to try to put it together before the weekend when the moon is almost full. Thanks for the tutorial and sharing your experience. Wish me luck!
Nice video Cuiv. If you want to improve further the flexture problem, you should consider replacing the TC40 carbon fiber tripod by a sturdier one. While it’s light and very portable it shows its limitations for heavier payloads such as the one you are using. Berlebach (from Germany) makes very nice ash wood ones, with an option to have it fitted with an AM5 compatible plate. I made the switch a few months ago and it considerably improved the guiding with my C8 and my TS photon 150 mm. In addition, it makes working on the telescope much more confortable. They are not very expansive, and if you can get them in Japan it is a no brainer investment.
Was just about to order a couple hundred bucks of stuff... then no! Cleared out my cart, came back here, and clicked the affiliate link first :) Thanks for the vids! Cheers from SoCal.
Thanks for the video! Note that you can remove the M42 spacer ring on the OAG base, this might get you close enough to focus. Also you probably know this, but raising/lowering the prism stalk assembly doesn't change the distance from the prism to the guide camera, so it won't affect guiding focus. For the backfocus distance, do remember to add roughly 1/2 of the thickness of the filter to the spec distance - my Chromas are 3mm thick, that would increase the actual physical spacing to 56.5mm or so. Might not matter at f/4, can make a difference on very fast optics (f/2 - 3 ish). OAGs are essential for many scopes, especially SCTs where mirror wobble as the scope tracks can result in differential flexure with guide scopes, especially over the 15-30 minute exposures that I typically take for narrowband. I don't know if mirror wobble would occur with your Newt, or if flexure from the focuser drawtube might have caused your issues, as the gravity vector changes as the scope tracks. Flex in the spider assembly also can cause issues with some Newts, especially if the secondary assembly is heavy or the spider vanes are not adequately tensioned, or insufficiently robust.
Thanks for all these additional information! And yes I have a whole video (from 2020) about the impact of filters on back focus, demonstrated mathematically haha
With many focal reducers, especially those that act as a field flattener you'll have specific backfocus requirements you'll want to adhere to so that the stars in the corners don't appear stretched. When you add the OAG to the imaging train you'll have to reduce the distance after the reducer by an equal amount to that added by the OAG.
So thankful for your channel @CuivTheLazyGeek I like full moon sessions too. We always seem to get clear calm nights then too. Nice to be able to use that time to experiment and learn.
Thanks so much Cuiv...very informative video as always... I have the OAG sitting in the box for some time now.... Your video explains all the intricacies involved with properly setting up this device.....
Hi Cuiv! I'm glad you figured this out as guiding issues can be quite annoying! I was looking at Askar's OAG and it looks pretty good as well! Hope the typhoon will pass soon but you sound is pretty good considering all the wind! Thanks and clear skies🌅
Excellent video once again Cuiv. I switched to OAG's a while back even on my wide field rigs. The combination of filter wheel, OAG and camera gives the required 55mm backfocus like you say (I also have a 0.6mm spacer to account for filter thickness). I also like the fact the OAG makes the whole setup more compact compared to having a separate guide scope.
I switched to an OAG, i honestly haven’t noticed a significant performance improvement but my mount is rather inexpensive & has a lot of backlash. That said i think it has improved my RMS, and in general i enjoy it over a guide scope because it’s lighter & I’m able to use my guide scope shoe as a spot for my pegasus astro power box! I think I’ll go with OAGs when i can from now on honestly.
My first usage of the ZWO OAG still needs to happen. I have tried to set it up the same way you have shown pointing my scope at something distant to focus the imaging camera first and then the guiding camera. Unfortunately to find something in a sub-urban area that is distant enough to get good focus with 1600mm focal length can be quite challenging. 😄 So I did the pre-setup with a ruler and a calculator. From the maths I am within 1mm range that both cams differ in terms of back focus. I hope that's good enough to quickly get focus for the guide camera once there will be a clear night again. I am waiting for 2.5 months now to get clear skies again. BTW: I am going to send you a photo of my 3d printed dew shield for my Skywatcher 150 PDS that does not require any additional material to mount it within the next days.👍
Always look foreword to your videos, entertaining and informative. I was considering a new guide scope so I don't have to change the ones I have over from one main scope to another but might fit one with an OAG instead now. Also, as autumn aproaches its one less lens exposed directly to the dew ladened air to worry about. ( had a lot of trouble with this last year, even with dew heating on the guide scope)
You made it look easy Cuiv! I had similar fun with co-focus with the flip mirror on my planet setup (always easier to acquire and center a planet with help of a widefield crosshair eyepiece). In that configuration I need to do PA and goto with the (innaccurately aligned) guidescope because the planet camera field of view is much too small behind the barlow.
Hehe, actually the first video of you I have learned nothing in, since I recently installed an OAG and read through everything that I could get. But as always the video was fun to watch and well made. Great you are back with us Newtonians 😅 clear skies!
The flexure is taking place at the main camera, look at the length of the imaging train with the heavy camera acting like a pendulum-as the telescope changes position during exposure-there is a minute flexure taking place relative to the telescope tube/optics. Using an off-axis guider eliminates this error because the guiding camera moves at the flexure. I found this out years ago when designing my square tube 12” Newtonian’s. I designed a sliding focuser/diagonal assembly which moved as the main focus keeping the camera etc as close to the scope ‘tube’ as possible, with fine minute focus tweak using the focuser. Result =perfect stars, better images being able to use a much smaller diagonal because my camera is very close to the square ‘tube’ rather than projecting an image all the way out to the camera as in your rig. My construction technique also uses a very shallow focuser, thus reducing the stick out etc. Greetings from Tasmania Australia 👍😁🇦🇺🦘
Yep, as I mentioned in a previous video, that was my suspicion as well - but others who own the same scope also suggested it was likely the tube itself was also flexing!
had that guide scope you showed at start. though gear lottery had mine with imperfection in the glass elements impairing guiding . and it tended to flex a bit so i 3d printed a clamp to clamp it into a finder shoe to avoid flexing.
Hi Cuiv ! First comment here (and almost first on YT), so first I'd like to thank you for all your content in which I've digged into for 2 years now, while going deeper and deeper down the rabbit hole :) About OAGs : I was thinking of getting one for my wide field setup (Askar FMA 180mm + PO imx533 camera + SA GTI). Guide scope works well but it is almost as big as the main scope, which looks a bit stupid :). Seriously, the idea would be to make the whole setup as much compact, balanced and lightweight as possible. In the other hand i fear the guiding is getting worse (the scope is supposed to be corrected for FF sensors though). Would you recommend using one for such purpose with such a short FL ?
Thanks a lot Cuiv for your video! Just a question: using OAG on long focal tube in a site with air turbolence, the guide camera could have some problems following a star "blurred" or moved by turbolence? Is not better a lower focal ratio for guiding? Marco
Had some trouble getting my OAG setup on my RC-8 - watching your RUclips suggests my camera may not have been orientated correctly! Hoping to try again next time its clear - Thanks!
An OAG can be more expensive, than just the OAG. I have the same OAG what you have sitting in a box for over a year now. I tried it 3 times but there was a lack of stars, due to the zwo120mini guider cam is too small sensor. Important to have a guide camera with a larger sensor. I still have yet to purchase a larger sensor guider, because I got 3 of them - but they are all small sensors and I tried all 3 and only see 1 or 2 stars through the 1300mm RC and horribly out of shape. I guess I'm just reluctant to buy a larger sensor guider for $300-400 or a larger OAG.
I'm in research mode and have thought about an OAG as a good to get item. First time seeing the fine adjustment capability for the guide camera. Too bad it didn't work for your configuration.
Bonjour Cuiv, Merci pour cette super vidéo. J'aurais une petite question : comme le champ "vu" par la camera de guidage est orienté dans la même direction que le champ du télescope, ne rencontres-tu pas de difficultés à faire la calibration sous phd2 lorsque tu vises une cible proche du pôle céleste ? Utilisant une lunette pour le guidage, il m'est arrivé plusieurs fois que le logiciel refuse la calibration car l'étoile qu'il avait pris en référence ne bougeait pas assez étant donné sa proximité avec le pôle céleste. Cela m'obligeait à orienter la lunette de guidage dans une direction différente pour résoudre le problème. Comment résoudre ce problème avec l'OAG ?
Thanks for the great video Cuiv ! About focusing : everytime you change the filter, your EAF would run a new autofocus, therefore changing the focus of your complete imaging train, including the guide camera. Do you manually refocus your guide camera after each filter change ?
Hi Quiv - a quick question as I set up a new AOG. I read that having a filter in the image train adds to the back focus requirement - so a 3mm filter for example, would extend my back focus by 1mm from 146mm to 147mm. I originally thought the filter accounted for 1mm of the back focus requirement, so I've actually been 2mm out of focus. Is my new understanding correct - it's additive? Thanks as always, Greg
This is one spot where I've really struggled. I bought a thin OAG for my 1000mm reflector and just continually struggled to find stars to guide from if I wasn't in a really dense star field. Unfortunately because I use my DSLR the spacing requirements are such that most OAGs just won't work (with a coma corrector) due to backfocus issues and I think that the options available just aren't great quality.
@@CuivTheLazyGeek That was exactly it I think - the prism was just teeny weeny and couldn't pick enough of the sky to get a good look at the universe. C'est la vie.
Thanks Cuiv. Looking into going this route, but I'm afraid that I won't be able to put the OAG in front of my EFW. The reason is that my Altair Ha/Oiii and Sii/Oiii 4 nm filters reaches focus very similarly, while my Antlia Quadband filter always requires a fairly robust refocus. I guess that means I'd need to put the OAG closest to the camera, severely dimming the starlight for my Asi 290mm guide camera... 😢
Hi Cuiv, Did you end up removing the helical focuser and using the camera position for focusing? I seem to recall that there was an issue with the helical focuser? Or, just my bad memory! Thanks, Jim
"We're all masochists somehow" lol! Yes, every time I try a new thing I think how great it will be. At least now I know how much pain I should expect. First time focusing a guide camera? Only took 3 hours to figure it out. Focusing on Saturn last night with a C8 and 3x barlow.. only 1 hour. Love the hobby, love trying new techniques and gear. Glad I know now to drink a cup of coffee at sundown and prepare for a long (long) night. Btw, I personally prefer the ZWO OAG-L which I bolt directly to my EFW. It was frustrating with the ZWO OAG to deal with tilt and rotation from the two parts when travelling.
Cuiv, can I use a color camera (like ASI462) with OAG? I'am struggling to get a reasonable focus with my OAG and ASI462. The focuser doesn't work too, because I need to bring the sensor closer to the prim. Furthermore, the stars are very dim and often I don't even detect them, affecting the guider.
Fantastic video Cuiv! In addition to being an accomplished astrophotographer & genuinely nice guy, you are an excellent teacher!👍👍BTW, with the addition of the off-axis guider, what is the total cost of all the modifications you have made to ensure that your 150P Newt is a reliable, high-quality image system?🤔p.s. I hope the typhoon does not affect you too much!🙏
Thank you for your very interesting video (as always for your videos) I have a question the C6 has a focal length of 1500, can you capture stars with the OAG, I heard that with such a focal length it was not possible to use an OAG?
Very good instruction for us noobs going all-in 😊 I plan to use the standard (old) ZWO OAG+ASI120MM, SVBony filter drawer and standard first ring=total focal length 55mm on my ASI 585MC Pro. The helical focuser from ZWO looks so nice, but will it not work in this setup?
I have the ZWO OAG for years... and I hate it ;-) but its not the OAG's fault... imagine you have big SCT's 2000+mm focallenghts (thats where the OAG is a must have) so there are already not much stars around, then combined with a camera like the 120mm you are just lucky to see any star. so choose your OAG camera wisely (choose not the smallest sensor...) and maybe better go with the OAG-L with the bigger prism. I really don't like to adjust my composition based on guidestars visible in the OAG rather than my own artistic choices. btw. I use the exact helical focuser you wanted to use. you have to insert the camera as far as possible into it and it should work but it will be depending on the camera you use.
You may even have the old version of the ZWO OAG, which is horrible (didn't have the grub screws to actually stabilize the stalk)... If you have the backfocus for it, the Celestron OAG is amazing!
When the time comes, OAG is on my list. ZWO vs Celestron? Others have said they like Celestron. Have you had a chance to compare? The helical focuser seems to make sense. Would it work in other configurations? 8" SCT?
Yes, I've had the Celestron OAG. It's a tank and it's amazing and it's the single best OAG I have used. But it uses a lot of back focus, so it's better to reserve it for SCTs or Petzval design refractors...
Very true. Mirrors & lenses will always lag behind the changes in ambient temperature, so that alters the figure, quality of star shapes & focal length of the system, all of which will lead to subtle 'flexure' issues during exposures. Also, with the smaller than optimal thickness of primary mirrors that are often used today, the focal length of the mirror can change with changing orientation (which is why properly-designed, well-constructed 9 point or even 18 point primary cells are preferred with reflectors...)
Hey Cuiv, nice video! With a Quattro 250p (250mm 1000mm focal) and a ZWO 120mm as guiding camera would you suggest the use of a OAG rather than a guiding scope? My worry is to not be able to find some guiding stars when going after deep-sky objects with such a focal lenght; if so, what guidescope would you suggest? Thanks!
I'm used ZWO OAG on my 150pds with 750FL and found out that the ASI120MMmini doesn"t always find stars. But with a slightly better guide camera like ASI290MMmini i worked like a charm. My point is that the answer to your question maybe depends a bit on what guidecamera you are using.
I was wondering if all the weight on the focuser can cause flexure problems in the image train. We have the same "no good" focuser on the Quattro 150P and I'm afraid this can lead to poor FWHM and Eccentricity... could you evaluate this? and, as always, keep up the good work!!!
Hi Cuiv, thank tou for the video. One thing that made me stop using OAG was the narrow band filters have focus offsets so if I was in focus on one filter when refocusing when changing filters makes oag out of focus. Any thoughts on that?
OAG can deal with some small focus changes - so if the filters are more or less parfocal (the same thickness) it shouldn't be a big issue. Were you using different brands?
Very nicely made tutorial. Thank you very much! I have some questions regarding your choice of equipment and setting. First why this specific guider instead of an OAG with a much larger prism that would be better suited to the fast guiding required by your mount? Also, why bother with M42/M48 connections when there are options to connect OAG, filter drawer/wheel, and camera with M2.5 screws? Finally, since you have a filter drawer, shouldn't you account for the glass in your back focus distance and have 56mm instead of 55mm?
- back focus distance, other OAGs tend to be too thick. Also this OAG is cheap! - because this OAG doesn't have the screw options, it's not the OAG-L - yes, and I do, I can't make things too complex in a single video :) And it doesn't change things much at F4 at least for this telescope
Excellent video mate! I have a 2350 mm Celestron SCT but I also use it with a Hyperstar lens which takes the FL down to 517 roughly. I want to be able to guide in both cases. Should I be able to purchase just 1 configuration to do both?
I'm using (or trying to use) an OAG with a FRA500 and its reducer. The big problem is that I'm having massive comma at the guiding camera. In theory, the prism is inside the image circle that the reducer should deliver with flat field. What could be another reason for this trouble? May the prism be with a failure? Backfocus? I'm using Player One FHD-OAG MAX.
Hi Cuiv! one question: I'm planning to buy the zwo am5 and I have a Newtonian 650/130. Do you think that is necessary to buy the pier extension for the mount? Because I see that you are not using it even with your telescope which is slight bigger than mine.
i just updated pixinsight ( that was a bad idea) iv'e now lost ez processing suite do you know of a fix or replacement &/or do you have a tutorial that doesn't use ez thanks
Amazing timing, Cuiv! I just got my EdgeHD 8 a few days ago and have been testing it and I've been talking myself out of trying the OAG I got with it in favor of a familiar guide scope/camera. Time to stop wussing out, I think, and put the OAG in the image train. Of course, using the external guide scope (an AT60EDR with a LONG focuser tube hanging out 🙄) I noticed elongated stars, even though the total RMS guiding error with my AM5 was in the vicinity of 0.4" for a good amount of the time. What did I expect with the saggy focus tube? Anyway, thanks for the 'encouragement' from afar! I'm going to try out the OAG and just bite the bullet and iron out whatever issues arise.
Ooh yes I had the EdgeHD8 a long time ago and an OAG is critical! The Celestron OAG by the way is a work of art, and when paired with a large sensor guide cam like a 174 it works beautifully!
@@Dennis-tf2cs Thanks, Dennis. Yes, I have the Celestron OAG paired with an ASI174MM Mini. So far tonight, the guiding has been under 0.5" total RMS (usually about 0.4") with the 0.7x reducer. (The RA and DEC have been pretty much equal and around 0.25-0.30" each.) I think so far, so good! The OAG seems to be making a definite improvement.
@@CuivTheLazyGeek Indeed : 66cm for standard, 68cm for the big one ( if i'm right ). It's good for RC, refractors, not newtonians. The main interest is that you uses the guide camera with short frequences to control. A diffraction cross is created and the soft controls the shape that varies with the focus error. As an example Peter Rejto, a TEC APO 180FL owner uses this system with excellent results. But there's an accessory, a special lens to screw in the guide camera that creates the same cross able to be controlled by the soft. With this, you can use it in the OAG system, i.e. newtonian... Is it worthy compared to our regular system ?
What is a full well capacity of the camera that needs 5 or 10 minutes exposure time? Imaging from light polluted areas adds even more constraints. OAG appeals because the setup is more compact, I don't know if there are additional benefits in terms of more accurate tracking
Another great video. One of the problems I seem to be having is that even though my filters are supposed to be parfocal, there is some slight change each time a focusing routine is done at filter change, and that throws the OAG camera, which is in front of the filters off a little bit. I then have to refocus the OAG by hand. Do you find that same issue?
PHD2 is fine with stars slightly out of focus - unless you have wildly different filter thicknesses, I find I don't need to refocus the OAG - it still works fine.
Would you be willing to share your AsiAir settings for the OAG guide cam when used with the AM5? I have a similar setup and am struggling to dial in my settings. Looking for your values for: Calibration step time, max DEC duration, max RA duration, Bin2 or not, stability, settle time, timeout, guide cam exposure length, RA aggressiveness, DEC aggressiveness.
Almost. the issue with the duo is you can't place the guiding camera in front of narrowband filters and therefore there is not much light hitting the guide sensor BUT most of the time it is still working fine.
My OAG + guide camera added too much weight to the focusing assembly on my MN190. Ended up ordering the ASI2600mc Duo to see if that will work instead.
ZWO 1,25" helical focuser seems to be totally useless with the OAG. It's frustrating to see my ASI290MM Mini camera can't reach focus due to the excessive length of the focuser and the weird mushroom shape of the camera. Did ZWO even test it?
Have you had a chance to test it under the stars yet? I'm curious star shapes on the guide camera. I've had issues getting decent star shapes using an OAG with this scope. Probably my issues we related to collimation more than anything. Having said that I know star shape shouldn't be SUPER important, but I've seen super weird shapes and it feels like the seeing conditions would cause those shapes to change which in turn makes PHD2 affect it's centroid calculation, as a result I have had way worse guiding using a OAG than a separate guide scope. But I really would like to get it to work in particular with this scope. I think these thin rolled steel chassis can have flexture in themselves which can cause issues with guiding. I've had the most success pairing this scope with a Evoguide 50 guide camera.
Yeah I was operating off that same thought process but in practice my guiding was way worse. As I mentioned it may have been mostly collimation issues that were my issues which was throwing the shapes WAY off.@@realmcerono
It only depends on the size of the OAG and the side of the sensor. The shape doesn't really matter - current square sensor would be the 533, which is relatively small, so not an issue!
OAG is great and also cost effective ( no guide scope)..I made the mistake of listening to the armchair experts who tell you OAG is problematic ... I find if I have difficulty finding guide stars the problem is seeing and as such makes me question if I should be imaging...so far the plus side has all the ticks.
I can’t get my camera to show images during the day. You skipped over this on your video, can you explain what you used to capture the image and what settings you needed for it to not flood the sensor? I also think I need to move my primary mirror inwards to get the offset the same between the cameras. Is there an easy way to measure from the prism to each camera chip?
I thought that TP's guiding camera would have a focus issue with other brands' OAG because of the "short neck". it would result in a longer back focal distance.
That's exactly the issue I'm having here (although Touptek guide camera), so I couldn't use the helical focuser - still in the end it was easy to focus :)
And how about reframing? I suppose that if you rotate camera only you may get obstructed by prism. Rotating camera and OAG you need to recalibrate guiding...
@@CuivTheLazyGeekha, fair enough. I ask because I've also got the AM5, and I'm near the 20kg limit, so just curious as to how much you've pushed the weight. I've seen the performance drop the heavier I've gone (obviously!). All good though, good luck!
1. Terrible star shapes and wrong center calculating in phd2 with atmosphere turbulence. 2. Sometimes there is no stars in field of view with 120mm camera and 200/1000 newt. 3. Focusing main camera = defocusing guiding camera. 4. Darker image in guider. Happy with 60/240 hard fixed guider at the lossmandy plate on top of tube rings. Get 0.4 rms at heq5pro and no trailing stars. Guider and main scope are collimated, and good polar alignment, of course.
Glad it's working for you! My stars in OAG are very round with no issue in PHD2 (at least for now!) and my shorter FL will make it easier to find guide stars during the galaxy season :) My guess is your newt is of better quality than mine too :D
Off axis guiding doesn't need to be complicated!
If you use an SCT or have a lot of available backfocus, I highly recommend the excellent Celestron OAG paired with a large-sensor guide camera:
Celestron OAG: bit.ly/44yqc9a
Large sensor guide camera: bit.ly/3P2Ps1s
ZWO OAG base: bit.ly/3qTetnY
ZWO Helical Focuser: bit.ly/44u8weT
Or High Point Scientific: bit.ly/3sEf39t
Support me on Patreon!: www.patreon.com/cuivlazygeek
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Saturn in opposition and Jupiter in opposition soon. Any chance of planet capturing comparing different camera manufacturers? Asiair planet capturing and stacking? Also heard about a comet filter. Do they work?
The moon is very handy -- it gives you correct infinity focus (for the stars) and is easy to set up an OAG with.
That works too :D
I just started using OAG with my new FRA600. I am getting the best guiding I have ever had. Where I was getting 50 t0 100 RMS. I am now getting 20 to 50 RMS. I wish I had not let my worries get the best of me and prevent me from using OAG.
I often see that with OAGs as well!
@@CuivTheLazyGeek As for focus. I'm using an asi120mm mini. I took the black extension off and I was able to get focus. I'm using the Askar OAG with the helical focuser.
Happy to hear the OAG solved the problem! That’s great news! Every time I watch one of your videos I learn something new. I never dreamed of checking the imaging sensor position relative to the OAG prism. Will do that! Thanks, Cuiv!
So, your best system was Vixen. You are like magnet trying to move in this direction.
I glad you came to conclusion that CEM60, fastar, non-edge SCt are good, but “good” is not good enough.
What a coincidence. I just had the exactly same issue.
Since I usually only expose for 150-180s at a time, I never noticed it, but when I got the DuoNarrowband, I wanted to push for 5-10 Minute exposures.
And I also had completely unusable images, despite very good tracking. I am using a 8" Newtonian telescope with a 180mm guidescope.
People told me it has to be flexure, so I bought a new dovetail, which allowed me to actually screw it on the telescope rings.
But even then, I still had the same issue. A lot of testing and eliminating other issues later, I was just hit with frustration.
I then bought an OAG as a last resort, which sadly doesn't allow me to use a manual rotator anymore due to distance issues, but still I would never want to miss it anymore.
Sure, it was a little finicky to set up, but the first image I took filled me with pure joy.
A 15 minute exposure, with actually quite bad guiding (prob due to bad seeing) in comparison, and still I had perfect stars. Would never want to miss it again!
Right!! I'm so glad you could fix that frustrating issue! Apparently the OTA tube itself can bend!
I started with an OAG in 1983👍👍, never looked back, will never use a guide scope. The OAG is just so much more accurate.
Cuiv. The black ring at the bottom of the helical focuser is a 10mm T2 spacer. You can remove it (or add a thinner one) to make the focuser shorter (or longer with a thicker one). The ring is very tightly screwed on but can be taken off. I had the same problem until I realised this.
Thanks for the tip!! I'll try
Thats where I'm at. In 5th grade i bought my first telescope. A 4.5 inch orion short tube on an non mortorized eq mount. I never learned how to even polar align. I always star gazed but fell away from the hobby a bit. Ive had my seestar now ( which looking for videos helped me find your channel) i love it so much and I'm hooked again. Now I'm already putting together a shopping list of astrophotography parts. I want more clearity. More power. Control of what field of view i can have. And sharp sharp details. I'm thinking since I'm new i will probably get locked into the zwo-verse. But watching your videos and seeing you over come and learn things and sharing your knowledge is a god send. Lol anyway thays my pointless story. But i think this is many of us. Keep up the content :)
I'm so glad you shared your (not pointless!) story, it's this kind of feedback that keeps me going with the channel :)
@CuivTheLazyGeek thank you man. This is why community is great. Your passion helps us pursue ours and our positive feedback can help you. I watch my friend start a RUclips page. He has since stopped it because editing videos was just too much. So I understand it's not easy to stay at it sometimes. But trust me we all hope you will. Clear skies brother.
Your explanations are always so detailed and easy to follow and fascinating even though this is way more advanced than my star adventurer and recently acquired Vespera. Thank you!
Glad you like them!
Great review and overview of OAG! Been thinking about swapping myself not because of issues but just to keep things more compact and simple 👍🏼
It sure helps keep things compact, and another advantage is it can make guiding more accurate since it shares the focal length with the main scope :)
Take a look at askar OAG it is so much more robust and well made! Another thing is that Askar prism is 10x10 and zwo is 8x8. I have both and my guide precision sky rocket. Be sure you have low-bortle skies or a modern high QE mono cam. Saw a lot of folks having problems with a lack of guide stars due to low light even with 3s phd intervals.
Great explanation as always. I just received my ZWO OAG that I'm now attaching to my Quattro 150p following your directions
Have fun!
Thank you for that explanation Cuiv! My rig is an old Alt-Az Celestron NexStar 127SLT (1500mm, 5 inch Cassegrain), which doesn’t have an ST4 compatible port for guiding, but it has something in common with your rig, which lead me realise what was happening to yours. It’s the longer focal length than previously used small rigs. The greater it is, the more everything will need to be accurate in your rig. Every single thing that deviates, will be greatly exaggerated when the focal length increases.
I’m using mine mostly for planetary imaging, and to do so, I was also using a 5x TeleVue PowerMate. This would increase the focal length to the extremes for the lousy mount that I have, which by the way doesn’t even have a clutch to balance it, so I’ve been doing the balancing off mount before mounting the scope to it, and marking approximately how far I should move the dovetai. Anyway, when I was trying to focus manually, this absurd focal length, would make it impossible, because I also had the image at 10x on the back of my Canon DSLR, and a planet would disappear from view even with the slightest touch. I’ve since made a DIY focuser with a tiny stepper motor and an Arduino driving it, and I’ve resolved that, but what you were dealing with, brought back in memory all those issues I had to overcome, to (partially) fix the ones my rig had.
Glad to here the use of the OAG sorted out the guiding issues. They can be a bit of trouble to get setup initally but once working, they are great, especially for long focal lengths. I am using OAG's for my two bigger rigs, the Meade 10" SCT and my SkyWatcher Esprit 120 (probably not necessary for the Esprit but guiding is great and I can get up to 20min exposures on both rigs). I used to use the the smaller OAG from ZWO (looks like the one you have) but I found it was too easy to slightly push the camera off center because the OAG uses those three screws for attaching into the imaging train and it's not that easy to get them exactly even and therefore exactly straight. In the end I swapped it out for the OAG-L (now using them on both rigs) as I could bolt them to the filter wheels on the "camera" side and on the telescope side it's a screw together connector so I know everything is as straight as possible.
I'm so glad to see more experienced astrophotographers loving the 150P. I bought it last year (after SO MUCH research and back and forth) as my very first imaging scope and it's been performing amazing for me. It's nice to know my decision was sound and it's even better having people like you to now show me what I can do to make this little scope even better!
Always good to meet fellow 150Pers :D
I’m graduating from a 90mm refractor with guide scope to a 200mm f4 Newtonian and just purchased a ZWO OAG. Going to try to put it together before the weekend when the moon is almost full. Thanks for the tutorial and sharing your experience. Wish me luck!
Nice video Cuiv. If you want to improve further the flexture problem, you should consider replacing the TC40 carbon fiber tripod by a sturdier one. While it’s light and very portable it shows its limitations for heavier payloads such as the one you are using. Berlebach (from Germany) makes very nice ash wood ones, with an option to have it fitted with an AM5 compatible plate. I made the switch a few months ago and it considerably improved the guiding with my C8 and my TS photon 150 mm. In addition, it makes working on the telescope much more confortable. They are not very expansive, and if you can get them in Japan it is a no brainer investment.
Was just about to order a couple hundred bucks of stuff... then no! Cleared out my cart, came back here, and clicked the affiliate link first :) Thanks for the vids! Cheers from SoCal.
Oh wow, thank you so much! This is always super helpful, thanks for thinking of me!
Thanks for the video! Note that you can remove the M42 spacer ring on the OAG base, this might get you close enough to focus. Also you probably know this, but raising/lowering the prism stalk assembly doesn't change the distance from the prism to the guide camera, so it won't affect guiding focus. For the backfocus distance, do remember to add roughly 1/2 of the thickness of the filter to the spec distance - my Chromas are 3mm thick, that would increase the actual physical spacing to 56.5mm or so. Might not matter at f/4, can make a difference on very fast optics (f/2 - 3 ish).
OAGs are essential for many scopes, especially SCTs where mirror wobble as the scope tracks can result in differential flexure with guide scopes, especially over the 15-30 minute exposures that I typically take for narrowband. I don't know if mirror wobble would occur with your Newt, or if flexure from the focuser drawtube might have caused your issues, as the gravity vector changes as the scope tracks. Flex in the spider assembly also can cause issues with some Newts, especially if the secondary assembly is heavy or the spider vanes are not adequately tensioned, or insufficiently robust.
Thanks for all these additional information! And yes I have a whole video (from 2020) about the impact of filters on back focus, demonstrated mathematically haha
With many focal reducers, especially those that act as a field flattener you'll have specific backfocus requirements you'll want to adhere to so that the stars in the corners don't appear stretched. When you add the OAG to the imaging train you'll have to reduce the distance after the reducer by an equal amount to that added by the OAG.
Your video answered to all of my questions regarding OAG. Great job and thank you very much! 🙏🏼
So thankful for your channel @CuivTheLazyGeek
I like full moon sessions too. We always seem to get clear calm nights then too. Nice to be able to use that time to experiment and learn.
Thanks so much Cuiv...very informative video as always... I have the OAG sitting in the box for some time now.... Your video explains all the intricacies involved with properly setting up this device.....
Glad you found it helpful and good luck setting it up!
Hi Cuiv! I'm glad you figured this out as guiding issues can be quite annoying! I was looking at Askar's OAG and it looks pretty good as well! Hope the typhoon will pass soon but you sound is pretty good considering all the wind! Thanks and clear skies🌅
Excellent video once again Cuiv. I switched to OAG's a while back even on my wide field rigs. The combination of filter wheel, OAG and camera gives the required 55mm backfocus like you say (I also have a 0.6mm spacer to account for filter thickness). I also like the fact the OAG makes the whole setup more compact compared to having a separate guide scope.
Thanks Cuiv. Considering a guide scope, but this looks promising
Man, you always post videos at the perfect time because I was looking at OAGs about 2 hours ago 😂
Hahaha well now you have some more details - hope you get an OAG that works for you!
Gracias! No sabía los problemas de flexión que resuelve!
Excellent video. I look forward to adding an OAG to my setup
I switched to an OAG, i honestly haven’t noticed a significant performance improvement but my mount is rather inexpensive & has a lot of backlash. That said i think it has improved my RMS, and in general i enjoy it over a guide scope because it’s lighter & I’m able to use my guide scope shoe as a spot for my pegasus astro power box! I think I’ll go with OAGs when i can from now on honestly.
My first usage of the ZWO OAG still needs to happen. I have tried to set it up the same way you have shown pointing my scope at something distant to focus the imaging camera first and then the guiding camera. Unfortunately to find something in a sub-urban area that is distant enough to get good focus with 1600mm focal length can be quite challenging. 😄
So I did the pre-setup with a ruler and a calculator. From the maths I am within 1mm range that both cams differ in terms of back focus. I hope that's good enough to quickly get focus for the guide camera once there will be a clear night again. I am waiting for 2.5 months now to get clear skies again.
BTW: I am going to send you a photo of my 3d printed dew shield for my Skywatcher 150 PDS that does not require any additional material to mount it within the next days.👍
The entire OTA for budget newtonian telescope will flex, also primary mirror cell will cause some movement
That's another potential cause I no longer have to worry about :D thanks!
A fantastic video again. Thank you. I am going to move to an OAG. Thanks
Another one very useful video from this channel. Thanks a lot!
Always look foreword to your videos, entertaining and informative. I was considering a new guide scope so I don't have to change the ones I have over from one main scope to another but might fit one with an OAG instead now. Also, as autumn aproaches its one less lens exposed directly to the dew ladened air to worry about. ( had a lot of trouble with this last year, even with dew heating on the guide scope)
Glad this is helpful, and thank you for your support!
You made it look easy Cuiv! I had similar fun with co-focus with the flip mirror on my planet setup (always easier to acquire and center a planet with help of a widefield crosshair eyepiece). In that configuration I need to do PA and goto with the (innaccurately aligned) guidescope because the planet camera field of view is much too small behind the barlow.
Hehe, actually the first video of you I have learned nothing in, since I recently installed an OAG and read through everything that I could get. But as always the video was fun to watch and well made. Great you are back with us Newtonians 😅 clear skies!
Hahaha well done on your own research and installation!
Okay I'm sold on the OAG, thanks!
The flexure is taking place at the main camera, look at the length of the imaging train with the heavy camera acting like a pendulum-as the telescope changes position during exposure-there is a minute flexure taking place relative to the telescope tube/optics. Using an off-axis guider eliminates this error because the guiding camera moves at the flexure. I found this out years ago when designing my square tube 12” Newtonian’s. I designed a sliding focuser/diagonal assembly which moved as the main focus keeping the camera etc as close to the scope ‘tube’ as possible, with fine minute focus tweak using the focuser. Result =perfect stars, better images being able to use a much smaller diagonal because my camera is very close to the square ‘tube’ rather than projecting an image all the way out to the camera as in your rig. My construction technique also uses a very shallow focuser, thus reducing the stick out etc. Greetings from Tasmania Australia 👍😁🇦🇺🦘
Yep, as I mentioned in a previous video, that was my suspicion as well - but others who own the same scope also suggested it was likely the tube itself was also flexing!
youre reading my mind! i was just thinking about getting an OAG
Woohoo! Hope this helps you setting it up!
Such a great breakdown, Cuiv!
Thank you!
had that guide scope you showed at start.
though gear lottery had mine with imperfection in the glass elements impairing guiding .
and it tended to flex a bit so i 3d printed a clamp to clamp it into a finder shoe to avoid flexing.
Glad that worked for you!
Hi Cuiv ! First comment here (and almost first on YT), so first I'd like to thank you for all your content in which I've digged into for 2 years now, while going deeper and deeper down the rabbit hole :)
About OAGs : I was thinking of getting one for my wide field setup (Askar FMA 180mm + PO imx533 camera + SA GTI). Guide scope works well but it is almost as big as the main scope, which looks a bit stupid :). Seriously, the idea would be to make the whole setup as much compact, balanced and lightweight as possible. In the other hand i fear the guiding is getting worse (the scope is supposed to be corrected for FF sensors though). Would you recommend using one for such purpose with such a short FL ?
Excellent video Cuiv!😊 Quick question: If you push the OAG prism too deep, will this affect the resolution of your main camera? Thanks!
If you push the prism too deep, you will start seeing a shadow in your main image, together with a vertical diffraction spike on your stars!
Thanks for a great video and demystifying OAG for me 😊
You are so welcome!
This is very well explained as always. Great channel! thx
Glad you think so! Thanks!
Thanks a lot Cuiv for your video! Just a question: using OAG on long focal tube in a site with air turbolence, the guide camera could have some problems following a star "blurred" or moved by turbolence? Is not better a lower focal ratio for guiding? Marco
Had some trouble getting my OAG setup on my RC-8 - watching your RUclips suggests my camera may not have been orientated correctly!
Hoping to try again next time its clear - Thanks!
Good luck!!
That's great! I was just deciding whether to purchase OAG or not, and then I found your video, mate. Thank you!
Good luck setting yours up!
An OAG can be more expensive, than just the OAG. I have the same OAG what you have sitting in a box for over a year now. I tried it 3 times but there was a lack of stars, due to the zwo120mini guider cam is too small sensor. Important to have a guide camera with a larger sensor. I still have yet to purchase a larger sensor guider, because I got 3 of them - but they are all small sensors and I tried all 3 and only see 1 or 2 stars through the 1300mm RC and horribly out of shape. I guess I'm just reluctant to buy a larger sensor guider for $300-400 or a larger OAG.
I'm in research mode and have thought about an OAG as a good to get item. First time seeing the fine adjustment capability for the guide camera. Too bad it didn't work for your configuration.
I've ended up making it work - and there's also a new Touptek OAG that should be pretty nice!
Thanks Cuiv!
My pleasure!
Bonjour Cuiv,
Merci pour cette super vidéo.
J'aurais une petite question : comme le champ "vu" par la camera de guidage est orienté dans la même direction que le champ du télescope, ne rencontres-tu pas de difficultés à faire la calibration sous phd2 lorsque tu vises une cible proche du pôle céleste ?
Utilisant une lunette pour le guidage, il m'est arrivé plusieurs fois que le logiciel refuse la calibration car l'étoile qu'il avait pris en référence ne bougeait pas assez étant donné sa proximité avec le pôle céleste. Cela m'obligeait à orienter la lunette de guidage dans une direction différente pour résoudre le problème. Comment résoudre ce problème avec l'OAG ?
Thanks for the great video Cuiv !
About focusing : everytime you change the filter, your EAF would run a new autofocus, therefore changing the focus of your complete imaging train, including the guide camera. Do you manually refocus your guide camera after each filter change ?
Hi Quiv - a quick question as I set up a new AOG. I read that having a filter in the image train adds to the back focus requirement - so a 3mm filter for example, would extend my back focus by 1mm from 146mm to 147mm. I originally thought the filter accounted for 1mm of the back focus requirement, so I've actually been 2mm out of focus. Is my new understanding correct - it's additive? Thanks as always, Greg
This is one spot where I've really struggled. I bought a thin OAG for my 1000mm reflector and just continually struggled to find stars to guide from if I wasn't in a really dense star field. Unfortunately because I use my DSLR the spacing requirements are such that most OAGs just won't work (with a coma corrector) due to backfocus issues and I think that the options available just aren't great quality.
Thin, tiny prism OAGs on relatively large focal lengths are problematic indeed ..
@@CuivTheLazyGeek That was exactly it I think - the prism was just teeny weeny and couldn't pick enough of the sky to get a good look at the universe. C'est la vie.
Thanks Cuiv. Looking into going this route, but I'm afraid that I won't be able to put the OAG in front of my EFW. The reason is that my Altair Ha/Oiii and Sii/Oiii 4 nm filters reaches focus very similarly, while my Antlia Quadband filter always requires a fairly robust refocus. I guess that means I'd need to put the OAG closest to the camera, severely dimming the starlight for my Asi 290mm guide camera... 😢
I'd still recommend to have the OAG in front of the EFW... You'll just need to refocus it slightly when using the Antlia Quadband..
Hi Cuiv,
Did you end up removing the helical focuser and using the camera position for focusing?
I seem to recall that there was an issue with the helical focuser?
Or, just my bad memory!
Thanks,
Jim
Just curious if you have a 533 square sensor. Is there enough clearance or will the OAG cover part of the sensor?
Definitely enough clearance! The 533 is still a small sensor
"We're all masochists somehow" lol! Yes, every time I try a new thing I think how great it will be. At least now I know how much pain I should expect. First time focusing a guide camera? Only took 3 hours to figure it out. Focusing on Saturn last night with a C8 and 3x barlow.. only 1 hour. Love the hobby, love trying new techniques and gear. Glad I know now to drink a cup of coffee at sundown and prepare for a long (long) night. Btw, I personally prefer the ZWO OAG-L which I bolt directly to my EFW. It was frustrating with the ZWO OAG to deal with tilt and rotation from the two parts when travelling.
Yes if I did have the whole ZWO equipment I'd likely have gone with the OAG-L as well!
Hi, I wonder where you buy your newtonian hood? Is that a 3D printed one by yourself or a stock one? Thanks!
Cuiv, can I use a color camera (like ASI462) with OAG? I'am struggling to get a reasonable focus with my OAG and ASI462. The focuser doesn't work too, because I need to bring the sensor closer to the prim.
Furthermore, the stars are very dim and often I don't even detect them, affecting the guider.
Fantastic video Cuiv! In addition to being an accomplished astrophotographer & genuinely nice guy, you are an excellent teacher!👍👍BTW, with the addition of the off-axis guider, what is the total cost of all the modifications you have made to ensure that your 150P Newt is a reliable, high-quality image system?🤔p.s. I hope the typhoon does not affect you too much!🙏
Total cost of the 150P with the improvements (spider, mask, OCAL, OAG) would be around 900-1000 USD, still a pretty good price!
Thank you for your very interesting video (as always for your videos) I have a question the C6 has a focal length of 1500, can you capture stars with the OAG, I heard that with such a focal length it was not possible to use an OAG?
Very good instruction for us noobs going all-in 😊 I plan to use the standard (old) ZWO OAG+ASI120MM, SVBony filter drawer and standard first ring=total focal length 55mm on my ASI 585MC Pro. The helical focuser from ZWO looks so nice, but will it not work in this setup?
What magical microphone do you use where no wind noise is picked up in this video?
Derek! I use the AI Voice Isolation in DaVinci Resolve, it's amazing!
I have the ZWO OAG for years... and I hate it ;-) but its not the OAG's fault... imagine you have big SCT's 2000+mm focallenghts (thats where the OAG is a must have) so there are already not much stars around, then combined with a camera like the 120mm you are just lucky to see any star. so choose your OAG camera wisely (choose not the smallest sensor...) and maybe better go with the OAG-L with the bigger prism. I really don't like to adjust my composition based on guidestars visible in the OAG rather than my own artistic choices. btw. I use the exact helical focuser you wanted to use. you have to insert the camera as far as possible into it and it should work but it will be depending on the camera you use.
You may even have the old version of the ZWO OAG, which is horrible (didn't have the grub screws to actually stabilize the stalk)... If you have the backfocus for it, the Celestron OAG is amazing!
Cuiv!!! How’s the back feeling these days?
Great video thanks 🔭
Any time!
When the time comes, OAG is on my list. ZWO vs Celestron? Others have said they like Celestron. Have you had a chance to compare? The helical focuser seems to make sense. Would it work in other configurations? 8" SCT?
Yes, I've had the Celestron OAG. It's a tank and it's amazing and it's the single best OAG I have used. But it uses a lot of back focus, so it's better to reserve it for SCTs or Petzval design refractors...
An additional source of “flexure” I found was the settling of the primary mirror! OAG fixed issue since I didn’t want to snug the mirror too tight😊
Very true. Mirrors & lenses will always lag behind the changes in ambient temperature, so that alters the figure, quality of star shapes & focal length of the system, all of which will lead to subtle 'flexure' issues during exposures. Also, with the smaller than optimal thickness of primary mirrors that are often used today, the focal length of the mirror can change with changing orientation (which is why properly-designed, well-constructed 9 point or even 18 point primary cells are preferred with reflectors...)
So many causes! And a single fix haha
Hey Cuiv, nice video!
With a Quattro 250p (250mm 1000mm focal) and a ZWO 120mm as guiding camera would you suggest the use of a OAG rather than a guiding scope? My worry is to not be able to find some guiding stars when going after deep-sky objects with such a focal lenght; if so, what guidescope would you suggest? Thanks!
I'm used ZWO OAG on my 150pds with 750FL and found out that the ASI120MMmini doesn"t always find stars. But with a slightly better guide camera like ASI290MMmini i worked like a charm.
My point is that the answer to your question maybe depends a bit on what guidecamera you are using.
I was wondering if all the weight on the focuser can cause flexure problems in the image train. We have the same "no good" focuser on the Quattro 150P and I'm afraid this can lead to poor FWHM and Eccentricity... could you evaluate this? and, as always, keep up the good work!!!
Hi Cuiv, thank tou for the video. One thing that made me stop using OAG was the narrow band filters have focus offsets so if I was in focus on one filter when refocusing when changing filters makes oag out of focus. Any thoughts on that?
OAG can deal with some small focus changes - so if the filters are more or less parfocal (the same thickness) it shouldn't be a big issue. Were you using different brands?
Very nicely made tutorial. Thank you very much!
I have some questions regarding your choice of equipment and setting. First why this specific guider instead of an OAG with a much larger prism that would be better suited to the fast guiding required by your mount? Also, why bother with M42/M48 connections when there are options to connect OAG, filter drawer/wheel, and camera with M2.5 screws? Finally, since you have a filter drawer, shouldn't you account for the glass in your back focus distance and have 56mm instead of 55mm?
- back focus distance, other OAGs tend to be too thick. Also this OAG is cheap!
- because this OAG doesn't have the screw options, it's not the OAG-L
- yes, and I do, I can't make things too complex in a single video :) And it doesn't change things much at F4 at least for this telescope
Excellent video mate! I have a 2350 mm Celestron SCT but I also use it with a Hyperstar lens which takes the FL down to 517 roughly. I want to be able to guide in both cases. Should I be able to purchase just 1 configuration to do both?
Hyperstar sits in front of the objective lens, which makes it unsuitable for OAG use - so one scenario would be OAG, the other guidescope
Thanks! Makes sense!
What if I have a big filter wheel? That takes up 20mm of my back focus space? I would need a tiny OAG to make my back focus work!
I'm using (or trying to use) an OAG with a FRA500 and its reducer. The big problem is that I'm having massive comma at the guiding camera. In theory, the prism is inside the image circle that the reducer should deliver with flat field. What could be another reason for this trouble? May the prism be with a failure? Backfocus? I'm using Player One FHD-OAG MAX.
Hi Cuiv! one question: I'm planning to buy the zwo am5 and I have a Newtonian 650/130. Do you think that is necessary to buy the pier extension for the mount? Because I see that you are not using it even with your telescope which is slight bigger than mine.
ooh! I forgot to mention that my Latitude is very low: 8 degrees. (Trujillo, Peru)
i just updated pixinsight ( that was a bad idea) iv'e now lost ez processing suite do you know of a fix or replacement &/or do you have a tutorial that doesn't use ez thanks
Amazing timing, Cuiv! I just got my EdgeHD 8 a few days ago and have been testing it and I've been talking myself out of trying the OAG I got with it in favor of a familiar guide scope/camera. Time to stop wussing out, I think, and put the OAG in the image train. Of course, using the external guide scope (an AT60EDR with a LONG focuser tube hanging out 🙄) I noticed elongated stars, even though the total RMS guiding error with my AM5 was in the vicinity of 0.4" for a good amount of the time. What did I expect with the saggy focus tube? Anyway, thanks for the 'encouragement' from afar! I'm going to try out the OAG and just bite the bullet and iron out whatever issues arise.
Ooh yes I had the EdgeHD8 a long time ago and an OAG is critical! The Celestron OAG by the way is a work of art, and when paired with a large sensor guide cam like a 174 it works beautifully!
@@CuivTheLazyGeek Well , we will see tonight! Can’t wait to try it out. Thx so much again. You got me off my butt and everything is set up. 😊
The OAG will serve you well. Make sure the OAG has a larger prism and get the right camera for it.
@@Dennis-tf2cs Thanks, Dennis. Yes, I have the Celestron OAG paired with an ASI174MM Mini. So far tonight, the guiding has been under 0.5" total RMS (usually about 0.4") with the 0.7x reducer. (The RA and DEC have been pretty much equal and around 0.25-0.30" each.) I think so far, so good! The OAG seems to be making a definite improvement.
Thank you Cuiv.
What do you think about O.N.A.G. ( On Axis Guider ) ?
I think it's a great idea but I've never tried it! Last time I checked it did use a lot of backfocus, not sure if that's still the case
@@CuivTheLazyGeek Indeed : 66cm for standard, 68cm for the big one ( if i'm right ). It's good for RC, refractors, not newtonians.
The main interest is that you uses the guide camera with short frequences to control. A diffraction cross is created and the soft controls the shape that varies with the focus error. As an example Peter Rejto, a TEC APO 180FL owner uses this system with excellent results.
But there's an accessory, a special lens to screw in the guide camera that creates the same cross able to be controlled by the soft. With this, you can use it in the OAG system, i.e. newtonian...
Is it worthy compared to our regular system ?
What is a full well capacity of the camera that needs 5 or 10 minutes exposure time? Imaging from light polluted areas adds even more constraints. OAG appeals because the setup is more compact, I don't know if there are additional benefits in terms of more accurate tracking
Narrowband :)
Is back focus measured from the focuser to the sensor or from the coma corrector to the sensor? My coma corrector sticks out 45mm from the focuser.
From CC flange to sensor!
Thank you, I’m determined to make this work, so 83.2mm from CC to sensor 👍
My camera pushes my Crayford down even when I have my tension completely tightened. Any suggestions on what to do?
Another great video. One of the problems I seem to be having is that even though my filters are supposed to be parfocal, there is some slight change each time a focusing routine is done at filter change, and that throws the OAG camera, which is in front of the filters off a little bit. I then have to refocus the OAG by hand. Do you find that same issue?
PHD2 is fine with stars slightly out of focus - unless you have wildly different filter thicknesses, I find I don't need to refocus the OAG - it still works fine.
You're welcome!!
Would you be willing to share your AsiAir settings for the OAG guide cam when used with the AM5? I have a similar setup and am struggling to dial in my settings.
Looking for your values for: Calibration step time, max DEC duration, max RA duration, Bin2 or not, stability, settle time, timeout, guide cam exposure length, RA aggressiveness, DEC aggressiveness.
I don't use the ASIAir with this setup...
@@CuivTheLazyGeek Okay then, maybe your NINA settings? They should still work as it's the same basic setup, and same mount.
Would the new ZWO Camera with guider built in have the same effect of fixing this issue?
Almost. the issue with the duo is you can't place the guiding camera in front of narrowband filters and therefore there is not much light hitting the guide sensor BUT most of the time it is still working fine.
My OAG + guide camera added too much weight to the focusing assembly on my MN190. Ended up ordering the ASI2600mc Duo to see if that will work instead.
The Duo looks really neat! Finally with recent CMOS technology the idea became viable :)
ZWO 1,25" helical focuser seems to be totally useless with the OAG. It's frustrating to see my ASI290MM Mini camera can't reach focus due to the excessive length of the focuser and the weird mushroom shape of the camera. Did ZWO even test it?
What about cameras with more than one sensor like ASI2600MC DUO? Have you tried one like that?
Not yet, I want to though!
Have you had a chance to test it under the stars yet? I'm curious star shapes on the guide camera. I've had issues getting decent star shapes using an OAG with this scope. Probably my issues we related to collimation more than anything. Having said that I know star shape shouldn't be SUPER important, but I've seen super weird shapes and it feels like the seeing conditions would cause those shapes to change which in turn makes PHD2 affect it's centroid calculation, as a result I have had way worse guiding using a OAG than a separate guide scope. But I really would like to get it to work in particular with this scope. I think these thin rolled steel chassis can have flexture in themselves which can cause issues with guiding. I've had the most success pairing this scope with a Evoguide 50 guide camera.
as you said, starshapes shoudn't matter for guiding. my stars looks mostly horrible in the OAG and guiding is totally fine.
Yeah I was operating off that same thought process but in practice my guiding was way worse. As I mentioned it may have been mostly collimation issues that were my issues which was throwing the shapes WAY off.@@realmcerono
Back when I was using the EdgeHD800, my star shapes in the OAG were terrible (like little comets) but the guiding was working without issue :)
Would a camera with a square sensor be blocked by the OAG prism?
It only depends on the size of the OAG and the side of the sensor. The shape doesn't really matter - current square sensor would be the 533, which is relatively small, so not an issue!
OAG is great and also cost effective ( no guide scope)..I made the mistake of listening to the armchair experts who tell you OAG is problematic ... I find if I have difficulty finding guide stars the problem is seeing and as such makes me question if I should be imaging...so far the plus side has all the ticks.
It can be finicky to set up for sure!
I can’t get my camera to show images during the day. You skipped over this on your video, can you explain what you used to capture the image and what settings you needed for it to not flood the sensor?
I also think I need to move my primary mirror inwards to get the offset the same between the cameras. Is there an easy way to measure from the prism to each camera chip?
I thought that TP's guiding camera would have a focus issue with other brands' OAG because of the "short neck". it would result in a longer back focal distance.
That's exactly the issue I'm having here (although Touptek guide camera), so I couldn't use the helical focuser - still in the end it was easy to focus :)
And how about reframing? I suppose that if you rotate camera only you may get obstructed by prism. Rotating camera and OAG you need to recalibrate guiding...
what's the weight of that scope/camera/focuser setup Cuiv?
I'm actually not even sure... because I use the AM5 as a mount I didn't need to care :)
@@CuivTheLazyGeekha, fair enough. I ask because I've also got the AM5, and I'm near the 20kg limit, so just curious as to how much you've pushed the weight. I've seen the performance drop the heavier I've gone (obviously!). All good though, good luck!
1. Terrible star shapes and wrong center calculating in phd2 with atmosphere turbulence.
2. Sometimes there is no stars in field of view with 120mm camera and 200/1000 newt.
3. Focusing main camera = defocusing guiding camera.
4. Darker image in guider.
Happy with 60/240 hard fixed guider at the lossmandy plate on top of tube rings. Get 0.4 rms at heq5pro and no trailing stars. Guider and main scope are collimated, and good polar alignment, of course.
Glad it's working for you!
My stars in OAG are very round with no issue in PHD2 (at least for now!) and my shorter FL will make it easier to find guide stars during the galaxy season :)
My guess is your newt is of better quality than mine too :D
@@CuivTheLazyGeek i think no - sw200pds without coma corrector)
@@cooltyn oooh the lack of CC would explain your OAG star shapes haha! But good you're not having troubleotherwise!