Lasers Lie!!.. And You Can't Ever Trust A Liar..
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- Опубликовано: 7 дек 2021
- Lasers for collimating your telescope sound like a futuristic way of going about things, after all, what can be more reliable than a laser beam for precision measurements.. Right.. Well no not really... Please watch and all will be explained...
I want to point out that this is an awareness video of what to expect (that they don't tell you about in the instructions) when using a laser for collimating your telescope.
Thank you for watching don't forget to subscribe as I do regular uploads for the new astronomer. Clear skies all :)
How to collimate a telescope without a laser part 1: • How To Collimate a Ref...
How to collimate a telescope without a laser part 2: • Collimation Made Easy ...
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Hey Jason, thanks for putting up this video. I'm new to astronomy and got my first telescope 12" dob. I had NO IDEA my laser wasn't collimated. I tested it out and sure enough it was way off. I got my telescope properly collimated now and super excited to see the difference tonight!
Great channel. I have shared your frustration with lasers. I am also a great fan of the collimation cap, or it's fancier sibling the Cheshire collimator. One of your commenters made a very good point about rotation of the secondary, lasers don't help here and using a laser to align the secondary often messes it up badly, while it's telling you it's fine.
The problems you describe are surely the biggest frustrations with lasers. And it's worse than that if you have a sloppy focuser as well. I struggled with this for a while until I realised that none of that matters! We are so often told to adjust the secondary to get the laser dot in the centre ring of the mirror. But as you have shown, it wobbles all over the place, and trying to chase that by mucking about with the secondary will only result in a badly misaligned secondary and worn out collimation screws.
"Never chase a laser with a secondary mirror"
I've come to the conclusion that the secondary should ONLY be aligned with a cap or Cheshire. A laser simply isn't up to the job and no amount of shimming or fussing will get it right. It isn't even possible to get the secondary rotation right with a laser.
But the alignment of the secondary is not even all that critical to the final collimation, it's poor primary collimation that causes the coma. Once the secondary is set, it almost never needs adjusting.
Once the secondary is done, put in the laser. The dot will probably be out. That doesn't matter. We can get the dot in the centre simply by jiggling the laser and focuser a bit and tightening the screws. That is perfectly valid, as long as it stays there. When collimating the primary all we require is a "ray" from the center of the eyepiece to hit the centre of the mirror and bounce back to the centre of the eyepiece. Placing your eye at the centre of the focuser using a cap does exactly this. We can see the reflection of the centre of the cap, and the "ray" is just the line between the cap and it's reflection. If we see the reflection of the cap centered in the centre of the mirror, then the primary is collimated. A laser shining slightly off centre is the same as looking slightly away from the centre when using a cap. Jiggling the laser does not move it's central position in the focuser enough to matter, it only changes where the laser is "looking". So "look" at the centre of the mirror.
So why bother? For me, it is very useful for longer Newtonians where I can't look in the eyepice and adjust the collimation screws at the same time. I can see the laser collimator screen from the back of the telescope where I am doing the adjustments. Once I've adjusted the primary mirror I check that the laser is still in the centre.
I checked my Astro Essentials laser collimator (£45) and it was spot on at a distance of 7m. I have a Cheshire and a cap also which I use to collimate my Dobsonian. I have compression rings on my focuser and fittings and have virtually zero play. I use the Cheshire and cap and check with my laser. The laser comes into its own in the field in the dark and used with a Barlow lens
Hi Jason! Its always a joy to see your videos. I don’t like laser for collimating my newtonians, but a barlowed laser is a different story when collimating the primary mirror. I really like my Collimation cap too, so simple and precise.
Clear skies!
Sounds like using a Carpenter 'level' on a boat in the water.
Great instructions...down to earth style...staying on the topic and not gabbing is critical.
Nick, Saugus CA.
If you use a barlow with your laser, it doesn’t matter if its collimated or not. You will get a “donut shaped” reflection on the lasers target from your center dot on the primary. You just center that donut.
Thanks for saving me there. I was planning to buy one for my reflector telescope and luckily found your video, otherwise my money would go to waste.
As you recommend in another video....A clear film canister with a grey plastic lid is brilliant..( pin hole in the grey lid) it's possible to illuminate the cap with a small torch shining through the side of the clear canister.....it shows up really well on the secondary mirror ......you can get them if you ask nicely at a boots photography counter who still develop film ....I'm lucky because I still use film as well as digital!!!!! Great videos .
Love your channel. Totally respect your opinion(s). Having said that my cheapo SVBony LC was spot on right out of the box. Maybe I was just lucky. As for the play I just used equidistant strips of masking tape. The main thing I like about using the laser collimator is that with my 10" Dob, I don't have to keep going back to the eyepiece to check alignment as I'm making adjustments. Of course checking it at the end with your cap is just good common sense.
Hello Donald, Thank you my friend..That's the only problem with caps/Cheshire's if you have a telescope with a FL more than a 1000 mm you can't adjust and look at the same time but with anything less you can do both at the same time.
I use one. My first one was out, but they had glued in the screws. The second one was out even further, but I used a V block and a large amount of frustration to get it right.
I'd be careful about double sided tape and a shim. I'd go with a simple layer of tape, but not going over itself first.
I built mine up until it was a good friction fit, no thumb screws needed.
Lower end scopes may also be the Bird-jones style and you need to remove the lense from the bottom of the focuser. Funny no one really mentions them.
I'm with you Jay! I learnt the hard way, lol...I ONLY use the Cap now :}
Wouldn't a Cheshire have exactly the same problem? Wobble in the focuser isn't the blame of the Laser collimator, it's just more apparant and you can do something about it. Collimation caps aren't know for being very precise either tbh.
Same here. I tried the laser once and screwed up my reflectors so bad, that I had to start from square one. I can collimate the primary and secondary mirrors so accurate just with a collimation cap, that I sent the laser back.
My advice would be to dont buy a cheap crappy laser collimator or expect one to work on a crappy focuser. I have a Howie Glatter laser collimator and it does not need collimating. Having said that I agree 100% that you don't need one.
I don’t worry too much if the laser is out , I use in a 2” focuser with a 1.25 compression fitting adjusting so the laser turn slowly as long as the red dot rotates centrally within the primary circle,
This is the technique I've been trying. It was such a pain getting the red dot close to spinning down a 4 meter corridor, when it still spins a little in the telescope, I've just done my best to get it rotating around the center ring.
Then barrlowed laser technique, and or checking with the Cheshire
Really informative Video Jason thank you. What are your views on Cheshire Collimators ?
Hello Paul, Your welcome my friend. Cheshire are great, any form of collimation that doesn't require batteries or the thing that is going to collimate doesn't need collimating get's a tick in my book :)
Really enjoy all of your videos Jason.
Something I don't think you have mentioned and I believe it to be another major setback of laser collimators, is that they simply can't help with rotation of the secondary mirror.
It's possible to deliberately rotate your secondary incorrectly and then compensate by tilting with the three grub screws to get the red dot exactly in the centre of the primary (try it).
So while someone might think they are in perfect collimation, they could actually be losing an abundance of light because their secondary isn't rotated properly.
Even if you are aware of all the pitfalls of lasers that you have mentioned, and are super careful while using one. There is just too many things that can go wrong while using a laser (including Barlowed).
I like to align my secondary with a Cheshire sightube and then align my primary with a cap, works every time.
I can see the advantage of using a laser for a longer focal length telescope where you can't look through the focuser while simultaneously adjusting the primary mirror knobs. But I think this is only to get you in the ballpark, and you should definitely do a final check with either a Cheshire or collimation cap.
I hope someone reads this and saves themselves the money and headache.
Hello A B, Some great points and advice there, thank you for your comment my friend. :)
Can you explain how to fix a secondary mirror? I think I got mine out of whack, I got a laser collimator and a collimation cap but I dont have a cheshire, and also do I collimate the secondary mirror first, and do I turn the focuser in all the way or does it matter? Trying to do my Celestron Astromaster 130
What I found works for me, is one I have a focuser with a compression ring so thats spot on. And two, I always point the white face to the rear of the telescope every time, so when I collimate my scope, the laser is pointing consistently. I can understand why using one with a 2 screw eyepiece like this would be too inaccurate.
Although everything you say is true, I still find some value with a Laser Collimator if you have the patience to fiddle with it. I used masking tape to get it to fit snug enough that I didn't need to use the screw to lock it into place. And my brand new SVBony Laser Collimator came with poor collimation right out of the box. I drew about a 1/2" circle from about 1 meter away. I had it on the edge of my desk pointing down. Once I figured out that the laser dot was always on the high side, helped me know which of the three adjustments needed to be adjusted. And in about 15 mins I had it ready to go. I really don't know why SVBony covers the opening for these adjustments. It's as if the product they sell never comes out of collimation. Well, I know for a fact that is not true. But I just used an hobby knife to dig out the rubber type glue they put in the holds so I could get access to the small grub screws inside. I believe they are 2mm hex head screws. I ended up spending about 90 mins in total figuring it all out. But my 8" SCT finally did collimate and the star test yielded amazingly good results. I decided not to even adjust it as it was that close. I'd probably just make it worse. ;0)
Hey Jason great video and interesting what you say! I guess I'll stick with refractor easy to setup and observe straight away. It's amazing a cap is better so you'll safe money.
I just got the Huawei p40pro smartphone and it's awesome for astrophotography as I've took shots and thought this is going to he so awesome in extremely dark locations next year.
Collimaters I think are OK but you ever thought of pointing at polaris when your polar align your scope? Maybe it'll work nicely just point at polaris and see if it works.
Thanks for the video my friend and stay safe too plus clear skies!!!!
Hey Bushcraft, Thank you my friend. Yes I've heard a few good things about the Huawei P40 I've got the Huawei P smart the budget version but it still has a reasonable camera on it, it's what I do all my videos with.. Unfortunately I've not been able to do anything with Polaris for about 10 years, because were I currently live Polaris is totally blocked by trees.... Only a rough polar alignment for me. Take care buddy, clear skies :)
I agree I bought 2. Collimated one with alot of doing. I no longer use them. . Cheshire 👍
Thanks Jason, your videos are really usefull and clarifying for beginners like me. I have to say that your English it's also clear for a Spaniard and it helps a lot... Now waiting for a chesire tutorial ;)
Hello Gonguere. That's great to hear my friend and your more than welcome . Cheshire video coming soon so stay tuned 😀
@@smalloptics753 Sure my friend...
Hi Jay, I'm just wondering about what you were saying at 5:30 ish into the video? My initial thought was that a Cheshire collimator will also change how concentric it sits in the focuser as you tighten the thumb screws, and so will an eyepiece. Therefore if you treat the laser or Cheshire like an eyepiece and tighten it by the same amount as you would an eyepiece, then surely you should be fine to collimate for visual astronomy that way? I would say concentricity comes more into play for imaging where people have screw fit adapters. In that case peeps can use an Hotech laser which has a compression fitting which does away with the thumb screws adding tilt. I personally think collimated lasers are quite straight forward because you don't need to squint down a tube, but I wouldn't usually recommend one of the cheap lasers to beginners for the points your rightly mentioned. A 6 quid collimation cap and a final tweak of collimation on a defocused star is probably all you need. p.s. I didn't realise that brass compression ring fittings also prevented tilt! I thought they just stopped barrels getting scratched by set screws. Bonus!
Hey Chris, Quite true, all thumb screw focuses will push the eyepiece/cheshire of centre a little but the point I'm trying to make is which admittedly I should have made a little clearer is, in thumb screw focuses laser collimation is only as good as a Cheshire/cap. like I say I have put it to the test Cap V's laser and the result was negligible. Also I don't want newbies thinking they have to buy a laser to get good collimation. Honesty Chris I've seen some disastrous attempts at collimating with lasers in the past. And yes the good old star test is all beginners should concentrate on at first, after that they can take collimation to whatever level they want.... As long as they don't use a laser lol..
To prove to someone that a laser collimator gives a false sense of accuracy... Let them collimate their scope with it. And then play with their primary mirror set screws. Watch as the laser moves away from the center donut on the primary. If the laser collimator process were any good, no amount of adjustment to the primary mirror should change the secondary mirror away from its correct position. These devices invite people to mess with their secondary mirror much more than needed. People end up really cranking on the secondary screws and bend their secondary's spider, or put divots into the secondary's holder that make it hard to keep its position. I was at a star party where someone said their scope was collimated because they used a laser, but the planetary images were really poor. I put a collimation cap on and shined a red lamp down the tube. They could see for themselves that the cap said otherwise. I adjusted their primary with the cap, and the planetary views improved dramatically.
I use a Cheshire collimator for my 8" Dobsonian. That's good enough for me. ;)
do you know any areas i could store my telescope or where i should store it. Also like what room temperatures and etc
Nice video all of your points are valid but What if you can't see what's going on with the collimation through the collimation cap while working with primary mirror screws?
Then you just get someone to help or you go back and forth. That's my problem. 48 inch tube can't look down the focuser while turning the screws but once you see it moving no problems.
Hello Irfan. Like mark says is one option another is to use a eyepiece phone holder and use your phone as a monitor to see whats happening in the focuser. With telescopes under a 1000 mm fl you can look in the focuser and adjust at the same time :)
In honestly really thankful you saved me from buying one of those XD i still spent the money on a cheshire that turns out i dont need but god it would've been so frustrating trying to use one of those
I tried a laser collimator when I first started astronomy .It was Frustrating ,no matter what ,I could not get my primary mirror collimated .Then ,I read about using a camera film holder and put a hole on the bottom of the film holder and place it in eyepiece holder.I also put a round notebook sticked that used to fix notebook paper holes that torn to the middle of my primary mirror .After I did that ,I was able to collimate the primary mirror in no time .Old ways are the best ways ..I latter got a collimation cap,to use .still have the camera film holder with hole in middle of the bottom of film holder ,,in case I lose one misplace collimation cap
10:42 Jeez you've really got it in for lasers Jay lol have you had a bad experience with an expensive laser? I've owned both the Baader and Hotech and they were spot on for 80-100 quid respectively. Is there any chance you're getting a bit carried away there, or have you had a bad experience with something like a Howie Glatter ? :D
Ha ha ha.. Collimating a collimater...enough said..
I discovered this same issue with a laser bore sighter. Lasers are only as straight as their alignment.
Good video but the thing that is not explained only because it may not have been brought up is why the "Cap" design cannot be skewed? I would think that it is also not going to be a perfect fit? I see more videos here in show more so I will look at them first.
If you don't "shim" your eye piece, it will be out of alignment, as well. For the non-compression ring clamps, the single screw variety would theoretically align the laser or eye piece in the same location each time. After hearing people complain about collimating the lasers, I checked my SVbony laser and it was "spot" on at a distance of 20 feet (6+ meters), and that is more than acceptable in the much shorter distance to the primary reflector. It is certainly easier to make the adjustment from the back of the tube without moving back and forth to the focuser.
Hello Bill, Yes, all thumb screw focuses will push the eyepiece to one side a little but for visual astronomy you wont notice it , when it is important for accessories to be dead centred is for astrophotography... With telescopes less than 1000 mm you can adjust and look at the same time :)
i bought one of those and learned something very importent thing , my telescope was bird jones (powerseeker 127eq) , after trying varius methods for collimation i can tell from experience just using my eyes on primary and secondry aligment and fine tuning with dark sky using bright stars its works for me and im happy with my bird jones , it was a pleasant jorney to learn new things and ur videos helped a lot thank u, now im waiting my 8"dob to arrive
Wish you could still make a video using a Cheshire. Ive kinda got the basics of it. And everything looks pretty centered. I think I've got it okay in collimation. Haven't had a clear night to check it out yet. But today is got dark blue skies and no clouds. Hope that holds up till tonight.
Hello Mark. stay tuned buddy I'm hoping to do a Cheshire video soon... Me too pal hope those clouds stay away for you.
@@smalloptics753 thanks buddy. I can already see Venus sticking up and a little bit of the moon.
@@smalloptics753 thanks Jason. Man I think I might have it pretty descent in collimation with the Cheshire anyway. I got to see Jupiter tonight and the moon. So cold it was hard to stay out long. My scope is f8 in skyquest xt6. But it has the metal focuser. Heard some bad things bout the plastic focuser ones. But thanks for all your help.
Great videos. Can you turn the gain on your mic down a little before you record? The crunchy sound you hear when speaking loud is clipping. Signed, a fan and audio engineer.
Apologies Chris I know.. I need to get a new mic the one I'm using is only a budget one, cost me about £30 and at the moment I'm using my phone as a camera and there is no way to alter the gain. I am getting a little better with it now by not having it so close to my mouth and have to point it away from my voice so it doesn't over mod, but of course the problem with that is I pick up all the rooms Echo. Like I say I really do need a better equipment all round. Hope it's not affecting your viewing too much my friend.. Sorry again.
Thanks for these videos Jason but I have a question, just acquired a Bird-Jones with a spherical mirror rather than parabolic, is collimation process a) necessary b) same, as this type aren't true newtonians ? Thanks
Hello Paul, Yes you still need to collimate a bird-Jones but to do it with a laser you have to remove the lens that is in the focus tube. Don't worry it's not as scary as it sounds. Take a look at this video and it shows you how to go about it. Hope this helps :)
ruclips.net/video/5yLJh31bWNQ/видео.html
Hi Paul, i also have a cheapo bird-jones and my advice would be to collimate it on a bright defocused star, laser won't work on it, also a pinhole cap is ideal for the secondary
Thanks for your responses. Jason, I was intending to use a cap for collimation as I've been scared off the laser option.
Michael DeSign Big, that was exactly what I was planning to do, many thanks
Are the 1.25” to 2” adaptors that come with these lasers trash as well. I need a converter anyway
Hello Matt, never used it but they seem ok, steel constructed the only down side I can see is they only have one thumb screw.. Which isn't a major issue I suppose :)
My laser is spot on, but I have the problem, that the alignment of laser and the secondary mirror changes while rotating the holder of the laser in the focuser. I put the laser centered in the donut. Everything is fine. I rotated the adapter of the laser in the focuser, and the laser beam was no longer centered because of slight decentralization in the adapter.
So is's literally impossible to center the laser, because the adapter isn't centered in the focuser. Does anyone have an idea?
Shimming the laser makes it not fit especially with the double sided even if you glue it on can you use masking. Tape as a shim
You need to collimate the laser to use it for collimating XD
tell you what, get 2 identical telescopes, collimate one your favorite way and the second collimate with a laser. I'm willing to bet you wont observe a difference at all.
Great Video Jason! I Use a Collimation Eyepiece Reticle. Its Similar to a Collocation Cap, But has Cross Hairs. I Also Don't Like Using Lasers, Because replacing those Batteries is a Lot of work!
Hey Avanteesh. Thank you my friend, That's the good thing about caps and Cheshire's, they don't need any batteries :D
Take 20 seconds to change the batteries
Thanks for saving me $35 Jason. Next time I’m in town I’ll buy you a cold one!
Hello Matt, Your welcome buddy.. Mines a pint a real ale :)
if you use a eye piece holder that has a compression fitting , it will go in the same every time , that's my first observation , keep in mind I only own refractors , for this very reason ....LOL
Hey Tom, Believe it or not I'm a refractor man at heart, there is a lot of faffing about with a reflector
Was recollimating my telescope today because my camera struggled to hard focus the moon and space. Figured collimation could be the issue.
Then i figured. A barlow lens without an eyepiece inserted, with the focuser fully extended afterwards. Allows me to easily see if the alignment of the primary mirror is wrong. As it kindof keeps the location of the reflection of the diag mirror in the same place without your head being aligned. Just need your eye to be 10cm-30cm away from it. Because of this it also makes collimation easier and less tedious as it gives your head slightly more freedom. Zooming out the focuser also makes the zoomed inn at the center. Making aim of primary mirror more accurate. Meanwhile if you adjust it in and out. You can also see the 3 clips and make sure the diag mirror also is properly aligned. This allowed me to make my best collimation attempt. And no modification to the barlow is needed.
For this i used my celestron omni 2x barlow.
Now after collimation. I took the barlow out and looked into the focuser. Now all clips are where pictures show they should be. Diag morror reflection is centered. And so is my eye reflection within it.
You don't like lasers ? so,...... you're not a Star Wars fan then ...LOL
Ha ha ha.. No, Star Wars I can cope with..
collimate the lazer then the telescope, yes it work....... probably not 🙃🔭👍
lol .. Collimating a collimater to collimate your telescope.. Just thinking about it gives me a headache..
@@smalloptics753 - you can collimate your laser.
Yes it takes a few hours and it's a very fiddly job but
it's worth every second of your time.
You must use a compression ring type focuser.
You can always finish the job off by putting a Barlow on the laser
to illuminate the doughnut on the mirror and adjust the primary
while checking in the 45 degree window of the laser.
Finally - use your Cheshire cap to confirm that the result is good.
yes useless things they are . i did get one used it once and sent it straight back lol
Just get a compression ring for £10-£15 from China problem solved
I have been doing ATM now 56 years, Laser Collimators are junk, they "wiggle in the focuser, and
therefore cannot be trusted, just take it out, re-insert and get new data, as a retired engineer, in my profession, they would be gone, JUNK, Needs to be reinvented,period.
do you know any areas i could store my telescope or where i should store it. Also like what room temperatures and etc