Perfecting Astrophotography Exposure Lengths - A deep dive into exposure times vs sub count

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  • Опубликовано: 23 ноя 2024

Комментарии • 196

  • @AstroWithRoRo
    @AstroWithRoRo  3 года назад +31

    Note: Bias/dark flat frames can help reduce the extra noise added from short sub length exposures, I will be exploring this in another video.

    • @jefflucas_life
      @jefflucas_life 3 года назад +2

      Enjoyed the informative tips for broad and narrow exposures, great refresher, I subbed 😃

    • @michaelbibby8636
      @michaelbibby8636 2 года назад

      Also, what was your guiding like for the 3 minute subs? One possible take away from this test is that your guiding is not as good as it could be.

  • @gregorymckenna6609
    @gregorymckenna6609 Год назад +3

    This topic is not talked about enough. Great that you are tackling it. Many will benefit.

  • @roymixon
    @roymixon 4 дня назад

    I'm new with EAA from last year staring May of 2023. Your video is grand! Glad I found your channel! Thanks for sharing and posting this. I learned a lot in such a short well explained video.

  • @JohnICGomes
    @JohnICGomes 3 года назад +17

    One of the best explanation I have come across on the net. Period!

    • @AstroWithRoRo
      @AstroWithRoRo  3 года назад

      Thank you!

    • @Astrospacegeek
      @Astrospacegeek 3 года назад

      Dr glover does a pretty good job

    • @AstroWithRoRo
      @AstroWithRoRo  3 года назад

      Much of this video is based off his work, I merely attempted to bring it all together and explain it in my own words :)

    • @ManishKumar-mw3sb
      @ManishKumar-mw3sb 2 года назад

      I didnt got anything

    • @ShorumTOO
      @ShorumTOO 2 года назад

      Quote!

  • @terrypowell8900
    @terrypowell8900 3 года назад +10

    This may be the best and simplest explanation of this issue I have come across. Excellent job!!

  • @oldrocker1970
    @oldrocker1970 Год назад

    Excellent video. 2 years old but still the easiest explanation I was able to find. I see a lot of people talking about gain/ISO, and that that should be part of the explanation. I disagree. First you figure out your exposure time, and then pick a gain to make sure you aren't clipping or over saturated. I come from the planetary imaging world where everything was super simple. Make your exposure time as short as you can (because that is frame rate in planetary imaging). We are trying to beat seeing, so ms level images. Then adjust your gain so you can see the image. That's why planetary cameras have their optimal gain up at 180-200. Hot pixcels be damned. We don't care!

  • @MikeHammer1
    @MikeHammer1 2 месяца назад

    When imaging deep sky objects with bright areas, excessively long exposure times can blow out the bright areas. Each camera imaging sensor has a limit to the number of photons a pixel can hold after which it becomes saturated.

  • @DiametralPitch
    @DiametralPitch 5 месяцев назад

    Absolutely fantastically explained video. You didn't leave anything out, something that's been missing from other videos I've seen. Loved the formulas and charts, and also liked the fact that you did a real test between two methods. The level of detail in this video made me sub instantly. Keep up the awesome content!

  • @aescaffre
    @aescaffre 2 месяца назад

    Really great and efficient way of putting it

  • @robertw1871
    @robertw1871 2 года назад +5

    Might be a good point to also include the difference in file size, 30 500s subs is not nearly as expensive as 500 30s subs when each frame is 50 to 100Mb each… All of the sudden you need 50 terabytes of storage, 256 gig of ram and 4 $2000 processors… And your image processing machine set you back $37,000 lol…

    • @rogerbarnett8412
      @rogerbarnett8412 9 месяцев назад +2

      Thibnk your math is off. by 1000x, 500 30 sec subs would be 25-50 gb, not tb...

    • @robertw1871
      @robertw1871 9 месяцев назад

      @@rogerbarnett8412 Read harder! Try a couple seasons worth of projects with 50 to 100meg files and hundreds to thousands of subs, it doesn’t take long. I’m living it my friend, 100TB NAS rack to manage 2 cameras! It’s not a joke. My math is exactly spot on! Last season I aquired 62.7TB of data.

  • @danjensen9425
    @danjensen9425 2 года назад +1

    Great video. Giving us something to work with is awesome. I have the 294 mm and mc. And going to a star party in Northern California end of June 2022. This is one of those videos I’ll watch a few times.

  • @user-gp3hv9fz2d
    @user-gp3hv9fz2d 5 месяцев назад

    I think, the less the time you expose, the more frames you acquire AND the most well-guided images will be taken. At the same time, you ensure your guiding will continue to be as desired, and the focus, as well, so lees frames to be thrown away. Flat fields are an absolute must (fortunately with NINA it seems to be relatively easy, as it calculates the ideal time per filter depending on the minimum and maximum time per filter you set).

  • @brianschumacher8751
    @brianschumacher8751 2 года назад +1

    Excellent video and thank you, was glad you mentioned Dr. Robin Glover. He has a great video that is very specific to exposure times. I have had good success with exposing at AVG ADU 1200 above the bias level on my 294MCPro. The exception is when I use my L-extreme filter as I am not able to achieve that level at a camera GAIN 125. I'm in a Bortel 5/6 zone and do not go over 3 min subs.

  • @Lukas_Hart
    @Lukas_Hart Год назад +1

    Interesting comparison, something I just started thinking about as I just got a tracking mount.
    But I think you got something wrong about why the long exposure image is less noisy:
    In general MORE IMAGES = LESS NOISE! Because the stacking software doesn't ADD, it AVERAGES the images. So the random noise in every sub exposure will be averaged in the stacked image and the signal to noise ratio improves. Otherwise there wouldn't be really a benefit of stacking images, except the clouds/shake problem you talked about.
    In addition, the noise in the short exposure time subs to me looks more like dark current/fixed pattern noise, what should be cleaned out by using darks (but you did)... maybe something went wrong there?
    I don't know the settings of both exposure times, but I would assume, that differences in photon noise had a great impact on your images. For people who don't know: There are several types of noise in your image, for example "read noise" (a.k.a. downstream noise, caused by the electronics of the camera after the gain/iso is applied to the signal before it reaches the ADC) and photon noise (caused by the effect that not every pixel was hit by the same amount of photons, so the pixel voltages varies to each other) and some more.
    Read Noise: The higher gain/iso you choose, the more the signal gets amplified before the read noise is applied -> less noise in the image.
    Photon Noise: The longer the exposure time, the less impact has a varying photon count of each pixel -> less noise in the image.
    So if your gain setting was the same on both exposure times I would guess it is mainly photon noise and bad SNR (more visible read noise) you see there. If gain was adjusted for the different exposure times, may be your darks calibration has something to do with that...(?) So for some reason your longer exposed subs are cleaner.
    I am not saying your test result is wrong/bad but your conclusion why the test result is like it is might be off. BUT for sure it is NOT less noise because you stacked less images! It's the opposite!
    Thanks for your video though! Cheers

  • @jeremyphillips1134
    @jeremyphillips1134 Месяц назад

    Excellent job. Thanks for posting.

  • @michael.a.covington
    @michael.a.covington Год назад

    The big thing here is that many mounts will give a high yield of 30-second exposures even if they can't track a 3-minute exposure perfectly at all.
    I strongly recommend using flats and flat darks. (Flats cannot be applied correctly without flat darks, required for the calculation.)

  • @kasparssmirnovs9482
    @kasparssmirnovs9482 2 года назад +1

    Well my exposures are usually 15-30 minutes, depending on object brightness, shortest i have done was 30 seconds on Cat eye nebula to get details in the middle :) Longest i went was 60 minutes for distant galaxy cluster :)

  • @CosminTruta
    @CosminTruta 3 года назад +1

    Very insightful and useful advice, many thanks!
    If I may please be pedantic with one small detail regarding the noise (R) factor in the minimum sub length formula (C times R squared over P):
    "[...] get the lowest noise that you can, because, as it gets higher, the squaring of it will make it exponentially worse, and you will want this to be as low as possible."
    I think you meant to say "quadratically worse", instead of "exponentially worse" ;-)

  • @2badger2
    @2badger2 Год назад +1

    I live in a Bortle 7/8 area and use a Optolong L-Ultimate 2" Light Pollution Dual Band Filter. How would the color camera (ASI2600MC) exposure numbers change? Thank you and thanks for sharing this video.

  • @Farathus
    @Farathus Год назад

    With faint objects i have run into dynamic range problems using short subs. If your Nebula just fills the first 100 buckets of your camera sensor well you will have to live with these 100 brightness values across the entire nebula. When stretching aggressively you will see banding. Long exposures avoid that by using more of the dynamic range of the sensor.

  • @georges3799
    @georges3799 2 года назад

    I miss the times I use to chill film emulsions with dry ice to reduce the effects of reciprocity failure during hour long exposures. Then all of the time spent in a dark room processing the plates.; and praying that my manual guiding was good enough for a solid image.

  • @kekkoukedarake110
    @kekkoukedarake110 2 года назад

    I greatly appreciate your explanation on this topics. Now I understand why my shorter exposures tend to be better than longer ones.

  • @mrutyunjaymishra351
    @mrutyunjaymishra351 11 месяцев назад

    To be honest, When I imaged the orion nebula, a 60 second exposure was way more vibrant than a 120 second exposure although the 120 secs was exposed for 30 mins, and the 60 mins for just 10 mins. For Bright Objects, short exposures are perfect. But when I went for the sculptor galaxy, a 60 second exposure absolutely failed to bring out much detail except for a bit at the centre. A 120 sec was much better and brighter, but still could not detail the outer edges of the galaxy. That is when you realise a 300 -600 sec exposure is perfect for dim objects.

  • @jimbob4484
    @jimbob4484 2 года назад

    That is super helpful RoRo. I am just getting going with Deep space astro. I have an ESPIRT 100ED/EQ6 mount +1600MM with all the bells and whistles, controlled with a stellarmate on rasbery pi. Got it all working for the first time the other week (after some very frustrating nights of getting nowhere) and got a shot of M42. Luminence turned out well (1 minute subs, 1 hour luminence/1 hour RGB) although it was a bit off centre and the bright core was a bit saturated(gain was a bit too high I think). My RGB channels were out of focus (I thought they were supposed to be par focal). This is the next stop for me, to optimise the exposure settings! Ive seen Robin's talk on youtube. It really cuts into the science of CMOS astro imaging. I come from a science and engineering background and even I will admit that it's not an easy topic. I think tutorials like yours are super helpful. You need a primer to begin with and then depending on personal interest, people can dig into the detail..... I am gona be compiling notes based on tutorials like yours and the work Robin and others have done ( whatever I can get my hands on ).... As is the case with astro, it an be days or weeks between imaging sessions ans so its easy to forget some of the fubdamental principles.

  • @wdavis6814
    @wdavis6814 Год назад

    Getting into mono and I've been taking notes using your videos. Super super helpful info! Thanks!

  • @fastamv.9896
    @fastamv.9896 3 года назад +3

    Yep, i guessed right but it was easy, you can clearly see you have pulled out more of the fainter details with the longer exposure.

  • @wimnelissen6230
    @wimnelissen6230 2 года назад

    Thank you for your very interesting talk, like the in depht explanation of exposure times etc. Wim Nelissen, The Netherlands

  • @rpg350
    @rpg350 2 года назад

    best explanation I've ever seen

  • @DeanJohnson67
    @DeanJohnson67 Месяц назад

    another reason to use shorter exposure length for me ... the planes flying over me on the way to chicago west - east or north - south to Milwaukee . fewer wasted frames > 120 seconds

  • @werdsmyth
    @werdsmyth 2 года назад

    I live in a Bortle 4 area. 180sec subs is my usual go to (with a OSC and pretty accurately tracking NEQ6 mount). Might reduce that to 120sec if I'm shooting something like Andromeda or Orion, or if the moon is above 50%. Might increase it to up to 300sec if I'm shooting a distance nebula with the L-Enhance filter. But I'm also a lazy astrophotographer and don't shoot bias or flats and also tend to borrow darks I've shot on previous nights under the same conditions.

  • @victorvillenapenas4274
    @victorvillenapenas4274 2 года назад

    Theoretically lucky imaging is the way to go if your telescope is sharp enough, even if it takes longer to image the same thing. On long exposures the best result you can achieve is the average atmospheric conditions which usually are way under the telescope’s potential. By taking loads of say 2/5 seconds exposures you can just take the perfectly sharp ones and avoid the ones blurred by instabilities in the atmosphere.

  • @robertopigini7277
    @robertopigini7277 7 месяцев назад

    Great explanation! Really helpful! Thank you so much.

  • @dummag4126
    @dummag4126 Год назад

    All people confused total exposure time with integration time. A 30 second exposure remains 30 seconds even with 100 30 second frames. 3000 seconds is just integration, not exposure. Exposure collects light, integration dusts away noise, improving signal-to-noise ratio, but does not increase exposure. I normally write like this: "photo x, exposure time 120 seconds, total integration time 3 hours". The longer an exposure of a single light is, the more light enters the sensor, as long as light pollution allows it. Integration lets you discover wonders that you didn't believe that your sensor was able to collect with such a short exposure. But you don't collect more light by integrating. This concept is so important as it is greatly misunderstood.

  • @entropytango5348
    @entropytango5348 Год назад

    Spot on all those details. Especially failure rates. I often vary exposures on a single object from 1 to 3 minutes (DSLR) during an imaging session (clouds, unexpected lights, etc). DSS stacks those without a problem but I'm unsure how that works in other stackers?

  • @JVRost
    @JVRost 2 года назад +1

    The shutter speed is increasingly dependent not on the illumination of the sky, but on the number of Starlinks))😆

  • @aj-astrophoto
    @aj-astrophoto Год назад

    Thanks for this very interresting video! It is very clear.

  • @mikemeal355
    @mikemeal355 3 года назад +1

    This has explained so much, thanks very much 👍

  • @fang8660
    @fang8660 3 года назад

    Very well made video, this cleared up a lot of my questions regarding this topic. Thank you for the info!

  • @spordniar
    @spordniar 3 года назад +1

    Absolutely amazing video! So well explained and easy to understand and follow.

    • @AstroWithRoRo
      @AstroWithRoRo  3 года назад

      Thanks for the positive feedback 🥳

  • @dustinkimball
    @dustinkimball Год назад

    Short sub minimum requirements = $300 uncooled camera, $400 budget mount, $400 small APO $100 flattener
    Long sub minimum requirement = $900 cooled camera ($1400 mono), $1200 mount, $400 small APO $100 flattener
    Unless you are VERY dedicated to the hobby or are willing to spend 3x as much for slightly better images,go for the short sub exposures. EAA is FUN and easy, astrophotography is challenging

  • @DIYTinkerer
    @DIYTinkerer 2 года назад

    You also need to factor in overheads such as download time, at very short exposures these can be considerable

  • @peterferguson4677
    @peterferguson4677 3 года назад +1

    Really useful video for someone of limited knowledge like myself..good stuff man 👍🏻

  • @ricardoabh3242
    @ricardoabh3242 5 месяцев назад

    Very inter and good for beginners like me

  • @davidaylsworth8964
    @davidaylsworth8964 3 года назад

    I just switched over from DSLR to TEC imaging and this video presents another piece of information for me to assimilate into my approach. With DSLRs I was pretty happy if I got 180s subs from my Bortle 8 observatory. With my ZWO ASI533MC Pro, 3 minute subs seem to leave me with bloated stars that are tougher to manage in PS. After viewing this video I will be working with much shorter subs on my 80mm f/8 refractor and LP filter, More like 60s to 90s or so. Great info to have for consideration. Thanks!

  • @filamentum0372
    @filamentum0372 3 года назад

    Great Video! Only one I could find that cleared up all my questions. Good job!

  • @David_Glazebrook
    @David_Glazebrook 3 года назад +2

    Thanks so much for the vid. I'm still in the DSLR arena and the principals of gear, conditions & experience are equally applicable. What changes perhaps is the recommended exposure times .... yes? Do you have a vid or other source you can point me to regarding this? Cheers :)

  • @josephluciani5531
    @josephluciani5531 3 года назад +1

    Thank you so much for making this confusing topic (for beginners) more understandable. Much appreciated!!!! Wondering how a light pollution, broad ban filter would alter the cheat-sheet exposure times (Bortle 7-8)?

    • @AstroWithRoRo
      @AstroWithRoRo  3 года назад +1

      Broadband imaging will need shorter subs, similarly the more light polluted your skies the shorter your exposures should be. If you add in a light pollution filter you can make your exposures a bit longer though since it helps to reduce the sky glow.

  • @orionm4268
    @orionm4268 3 года назад +5

    All in all, exposures depend on your bortel zone, your target, and most importantly your scopes aperture and your cameras pixel size, crop factor, and so on.
    There is no perfect exposure time as there is no perfect rig for DSO, planetary and so on.
    Astronomy like other fields has many rabit holes to go down.
    Clear skies

  • @gwthomas52
    @gwthomas52 3 года назад

    Great info. It helped to resolve a number of questions that I had. I just started with this hobby about 9 to 12 months ago, and I've struggle with determining my ISO and exposure times. Maybe a short comparison might be an interesting topic, or not.

  • @cwarrillow
    @cwarrillow 3 года назад +1

    If I take shorter exposures the histogram looks very low and not the normal third across the screen. Would this hurt?

  • @assaultpickle77
    @assaultpickle77 2 года назад

    Ioptron Skyguider Pro. Guidestar61 + field flattener. Stock Canon T7.
    =2 minutes subs.
    My best night of astrophotography ever!

  • @orionm4268
    @orionm4268 3 года назад

    Short exposures are good, just need more subs to increase signal.
    Also depending on wethor or not you are using an un-cooled camera, Long exposures past 5 minutes don't look to great because of the sensors heat, yes dark frames can help, but temperature isn't precise and connont be regulated easily with dslr's and so on.

  • @possummanrld
    @possummanrld 3 года назад

    Thanks for the well presented, balanced and objective information. In evaluating these types of videos, I honestly believe most of these crazy long exposure times, and, crazy amounts of hundreds or even thousands of exposures, is unnecessary overkill. And I think it is also at times the idea of a "look what I can do", attitude.
    So, I think I am more of a shorter exposure guy! ha! ha! But, each to their own. So, if 10 minute exposures makes someone happy, or if 1000 exposures is your bag, by all means, go for it! 😁

    • @AstroWithRoRo
      @AstroWithRoRo  3 года назад +1

      Absolutely, the choice is there to do either and it comes down to personal preference. Knowledge that you can do all/either is key as many think they must strive for very long exposure times.

  • @nitin_tag
    @nitin_tag 2 года назад

    Excellent explanation.

  • @acshaw80
    @acshaw80 Год назад

    Very helpful; you have a really great channel!

  • @MetalZlig
    @MetalZlig 2 года назад

    Very good video on this topic! :) I would just add that the lense f/ratio will also have an influence on the optimal sub exposure time.

    • @mif1118
      @mif1118 Год назад +1

      That is already included in the sharp cap calculation for the sky electron rate.

  • @DavidJohnson-xr7ep
    @DavidJohnson-xr7ep 3 года назад

    Id love if you'd do a video about how to find the best gain to set your camera at in some detail like you did for this video

    • @AstroWithRoRo
      @AstroWithRoRo  3 года назад +1

      This video may interest you, I talk about finding the best gain/ISO for cameras in it: ruclips.net/video/O05qb2XI2kk/видео.html

  • @komr323
    @komr323 3 года назад +4

    I think you have missed the key on sub exposure, which is brightness of the object. You definitely won’t expose the same time for m42 and sh2-240.

    • @AstroWithRoRo
      @AstroWithRoRo  3 года назад +2

      I may have skimmed over this a bit too quickly, but absolutely you do not want to over expose your images, even under dark skies. If you want to shoot something that has a lot of very bright stars, or a large dynamic range then you may need to keep your exposures very short, or shoot at two different exposure lengths and use a HDR method in post. I may create a video on HDR imaging and how to know if you're overexposing/blowing out your images. Thanks!

    • @erikahrend
      @erikahrend 3 года назад +2

      @@AstroWithRoRo Please do...

    • @padraickoen8949
      @padraickoen8949 3 года назад

      RoRo, first, great material and presentation. Like komr323's comment about 'object brightness', shouldn't 'light gathering capability' be a consideration? I'm thinking not only the focal ratio, but also the diameter of the telescope. I've used a C11 and a C14 each fitted with a Starizona Hyperstar lens, both resulting in f/1.9, and both using the same camera, a ASI1600mc, and both at the Arkaroola Imaging Observatory in outback South Australia where it is Bortle 1 or 0 (average SQM Maximum is > 22.0 mpass). But the C14 collects 70% more light per second than the C11. So, over-exposure is a consideration. In the evenings the equipment is used to give live deep space astronomy tours where audience's image presentation wait-time tolerance is less than 6 seconds. So, the C14 is much better at satisfying them. For my after-hours survey work, I continued to use 5 second exposures, except for bright objects, like Omega Centauri. An exception to that exposure length was when imaging M31, which I found 3 x 20 second subs were much better than 12 x 5 second subs (see www.flickr.com/photos/pkoen/50545716423/ for what that looks like from 30° South latitude).

    • @AstroWithRoRo
      @AstroWithRoRo  3 года назад

      This is starting to push my understandings, but from what I have researched, for extended objects like nebulae, the focal ratio, sky brightness and camera noise are all that really matter. Limiting magnitudes based on aperture is for stars/point sources. Limiting magnitudes on extended objects like galaxies and nebulae are based on focal ratio. So for extended objects, no matter the aperture size, if the f-stop is the same the nebulae brightness will be the same at the same exposure length. Your point light sources will get much brighter though so you will need to make sure these don't clip. Because of this, a larger telescope will be more likely to clip it's stars, so you may need to drop your exposure time to avoid this, but the nebulosity or galaxy views will be the exact same brightness between different sized scopes of the same focal ratio. This is actually one possible negative of large aperture scopes, you may need to image shorter than ideal times because your stars will slip too early adding in more read noise. Of course the benefit of a larger aperture (at the same fratio) is that you have a longer focal length, thus you will gain more resolution on the object you are trying to image. It's also why you can use a f/1.8 camera lens and get great nebulosity with short exposure lengths, but you sacrifice all the object resolution as the images are so wide with their field of view.
      I'm going to leave a link to a great thread on cloudy nights that delves deep into the reasoning behind it from people who understand a lot more than me on this topic: www.cloudynights.com/topic/630597-exposure-time-for-telescopes-with-same-f-ratio-but-different-focal-length-and-aperture/?p=8796287

  • @zbnmth
    @zbnmth 8 месяцев назад

    Overexposing subs is also a consideration!

  • @seanc8054
    @seanc8054 3 года назад

    i have been wondering this for so long, but nobody has ever really done it in this much detail, i dont have any experience with photographing stars, but i really want to try it, although the only DSLR i actually have is an old pentax K-5, which is i think a decade old now, or maybe even older

  • @roostaCSGO
    @roostaCSGO 3 года назад

    Great video, I have been trying to wrap my head around calculating ideal exposure times for my setup and until now I've been eyeballing it. I've been severely undershooting narrowband at 3-5 minutes and overshooting my LRGB at 2-3 minutes. With my location and my 183MM Pro @ F4.5 I supposedly should shoot for 14+ minute narrowband subs, 45 second RGB, and 15 second luminance. I think I'll shoot a bit longer LRGB than that though, while cutting back the narrowband. In any case, now I have some ballpark numbers to work with and hopefully this should improve my images!

  • @AstroCloudGenerator
    @AstroCloudGenerator 2 года назад +1

    Hi. I would love to hear your thoughts on varying the gain rather than exposure time when capturing RGB stars for a narrow band image. I have an ASI2600mm and am just getting a feel for it. I have clearly been overexposing my stars and the colours have suffered but I wonder if a lower gain would improve the colour quality more than shortening the exposure.

  • @AstroHunter5280
    @AstroHunter5280 2 года назад

    Ok, this is a great video and shedded some light on my process. Here is what I have:
    RedCat 51
    ASI 533mc
    30mm guidescope/ASI 290mm mini
    EQ6 Pro
    L-Extreme/L-Pro Filters
    Bortle 7 skies
    I have been shooting at a gain 100 x 300 second exposures. Are my exposures too long? Should i be following this 180 second threshold in my suburban area?

  • @matthewkendall5235
    @matthewkendall5235 3 года назад

    I think that is quite a helpful video - many thanks. I have multiple scopes in a small 2.3 metre astro dome I control remotely from my house. I most commonly image nebular using a Williams Optics FLT 110 pared to a ZWO ASI071MC-cool Pro camera and a 235mm Celestron Carbon Fibre F10 SCT connected to a ZWO ASI1600MM-c. I mount this and a Williams optics 98mm Doublet (the 235mm and 110 side by side, with the 98mm piggybacked on the 110) on an old Vixen Atlux mount controlled by a Vixen SkySensor2000-pc. I guide off axis from the SCT or on axis from the 98mm using a ZWO 120MM-s or QHY 5IL cameras respectively. With guiding I can go out to 30 minute subs and still get round stars - (but super saturated frames) So I know the tracking and guiding is really decent. I didn't know there was a light pollution map (big thanks you for that) that tells me I am in Bortle class 6 skies. Typically since moving from modded Canon DSLRs to ZWO cameras I have shortened my subs to 2-6 minutes - depending on how faint my target is. This has been all trial and error - your video gave me some science to tune into my experimentation - another big thank you. Lastly I haven't settle on single processing software yet. I typically transfer my images from my astrolab PC to a 8 physical core CPU with 64 GB RAM and 2 NVME drive and 4 SSDs to to stacking and processing. But I have only played with Deep Sky Stacker and an old Photoshop CS4 software to process my images. From your video I am sensing I should look at one of the big three astro image processing software suites - are you totally happy with PixelInsight or do you think go simpler? Many thanks Matthew

    • @AstroWithRoRo
      @AstroWithRoRo  3 года назад +2

      Sounds like you have some wonderful gear Matthew, I dream of having a permanent setup like yours! I'm so glad to hear the video helps you to narrow in on getting sub times that get the best results for your gear, it's amazing what these new cameras can do. I started with Sequator which was solid, but simple, you couldn't tweak a lot if the processing didn't end up how you wanted. DSS is quite good, but I found that I still had to bring things into PS to do all my colour correction. Pixinsights is great because it allows you to edit the images from FITs through to JPG. It's a very complex program though, so if you choose to use it make sure you're ready to read and watch a lot of guides and tutorials.

    • @matthewkendall5235
      @matthewkendall5235 3 года назад

      @@AstroWithRoRo many thanks - so as an interim step I went with Astro Pixel Processor as it is a lot simpler, I am rather time poor due to work loads and it is a lot cheaper. I think over time I will probably step up to Pixel Insight.
      On your imaging topic I wonder what advice you would give for capturing a nebulae within a star field? My thoughts are take maybe 20% of the frames or less to capture the star field - so as to have pin point stars - and use quite short shots - say 15 - 30 seconds - mask out the nebulae and have a layer just for the stars. Then for the nebulae is a question of 1) how much brighter than your background skies are they - so do you need to go narrow band and 2) else simply capture until the nebulae sets your cameras wells to about 70% - 80% in its brightest portion. Then sum up all your nebulosity layers - mask out the bright and bloated stars - process your nebula and add in the stars at the very end.
      If your nebula has a very high dynamic range - like say M42 Orion then you might have to split the nebula into two or three masked zones - which would make processing a tad more tricky. Wonder if you have played with this and have any advice to share on imaging objects with very high dynamic range and / or dealing with imaging in light polluted skies?

  • @SenpaiSkyy
    @SenpaiSkyy 7 месяцев назад

    So the 15 seconds is like lucky imaging then? It seems like it’s longer than like the lucky planetary imaging.

  • @dannychaing8428
    @dannychaing8428 3 года назад

    Excellent presentation and explanation! Much appreciated. I just became your subscriber.

  • @NebulaNestDIY
    @NebulaNestDIY Год назад

    I can find planets as well as many other deep space objects through various viewing lenses. When I take out the viewing lens and insert the camera I am clueless as to how to magnify the image so I can see it on the computer and phone APP's. The moon is easy enough to see and photo, but I can never see Jupiter or get it to come into focus. How is this done using cameras similar to the ASI 120MC-S model? I am very new at this!!

  • @daviddouglasuk
    @daviddouglasuk 2 года назад

    It would be really helpful if you could provide sub lengths for different setups representing beginner to pro. Starting with Sony A1 + 200-600 lens under a borle 4 sky.

  • @TeamGamingSWE
    @TeamGamingSWE Год назад

    Interesting, the light pollution map says my estimated SQM is 21.52, which equals to bortle 4 on that site. But on sharpcap tools it equals to a bortle 2.4? That can't be quite right?

  • @erikahrend
    @erikahrend 3 года назад +2

    Recently came across your channel, subbed! Thanks for the detailed explanation. When these issues crop up, though, there is always something that is not entirely clear. When you give the sub times for narrow band filters, I am assuming you are basing that on a mono sensor. However, there are many of us who shoot OSC with duo band filters (take the L-eXtreme, for example, which is 7nm in both Ha and OIII). If the calculated subs are for a mono sensor with a 7 nm filter, shooting the same 7nm filter with an OSC adds the extra filtration of the Bayer matrix, so how does that affect exposure calculation? Multiply (exposure time) by what factor? 3? Thanks!!

    • @AstroWithRoRo
      @AstroWithRoRo  3 года назад +1

      That's a very solid question. I hadn't thought about narrowband imaging on OSC cameras as I haven't done it myself. For this you can probably just take the 7nm times and be done with it. Since there's no overlap between the pixels receiving the Ha and pixels receiving the O3 it will work as if you had a 7nm Ha filter, then a 7nm O3 filter run on a mono cam. You will just lose some resolution due to the bayer matrix meaning the Ha red pixels are only 1/4 as numerous and O3 green pixels are 1/2 as numerous as a mono with the same filter. The image brightness of the red/green pixels receiving photons through the filter wont change compared to a regular 7nm on mono as far as I can tell.

    • @erikahrend
      @erikahrend 3 года назад

      @@AstroWithRoRo Thanks for taking the time to reply. What confuses me is that if you use the sky background calculator in Sharpcap, the values for unfiltered mono and either OSC or mono with RGB filter are different, so the RGB filters (or the filters in the Bayer matrix) seem to reduce the light in some measure...

    • @calvincarter5503
      @calvincarter5503 2 года назад

      @@erikahrend I'm probably not going to get this perfect, but that may be because when you are unfiltered mono, each pixel gets the full number of photons, whereas a bayer matrix will take the light and cut into 4 pieces (RGGB usually) and therefore each pixel is only getting 1/4 of the photons that the bare mono pixel would have gotten. So yes, the filter and the bayer matrix both reduce the amount of photons the pixel would receive.

  • @bengsynthmusic
    @bengsynthmusic 2 года назад

    Hello. So 12:03 let's pretend that there are no unwanted artifacts in that single exposure photo. Would it be fair to assume it would yield the best result?

  • @AmatureAstronomer
    @AmatureAstronomer Год назад

    According to the rule of 500, my 254mm reflector on a Dobsonian with a focal length of 1270 and an f5 has a maximum shutter speed of .39 seconds, before star trailing becomes and issue. Sad.

  • @einarschau
    @einarschau 2 года назад

    Great! Best wishes from Norway

  • @suzannebeers6238
    @suzannebeers6238 3 года назад

    Excellent explanation - thank you VERY much! Couple of quick questions... 1. You mention this is based on dedicated AP camera, are the same values for exposure time by sky conditions the same for astro-modified DSLR? 2. Is the brightness level of the target a factor in any way?

  • @pompeymonkey3271
    @pompeymonkey3271 3 года назад

    That was effing brilliant!
    This is using math to substantially reduce the impact of light pollution.
    I'd love a QHY600, but I think reality will constrain me to a 268!
    Add in quality NB filters (i.e.

  • @Thunder_Dome45
    @Thunder_Dome45 3 года назад

    Well that was thorough. Thanks.

  • @orionm4268
    @orionm4268 3 года назад

    Good explanation

  • @MrMrduke1975
    @MrMrduke1975 6 месяцев назад

    I’d rather use a lower exposure and get a more accurate detailed shot, than potentially blowing out my shot with an exposure I had no business taking. The hobby isn’t going anywhere. Take your time and enjoy your time under the stars.

  • @anzo.p
    @anzo.p 3 года назад

    I suppose one can just begin exposing 30 seconds, 60, 90, 120.. and observe when the background greyness peak begins to detach noticeably from the black end of histogram..

  • @valentinotera3244
    @valentinotera3244 2 года назад

    What about 1 trillion of 1/4000s sub exposure? Can you imagine how crispy details

  • @qonos68
    @qonos68 2 года назад

    Hello Rowan, just landed here from nowhere and this was the explanation video I've been looking for in the last 2 months! Absolutely clearly explained, thank you so much. I think there is a last point it could be interesting to deepen. Given the pro and contra of 60 15 seconds and 5 3 minutes exposures, in order to achieve the 5 3 minutes SNR, how many additional 15 seconds exposures would be required?

  • @MADHIKER777
    @MADHIKER777 2 года назад

    Well done! Thank you!

  • @kpritcha
    @kpritcha 3 года назад

    Do we also need to consider dynamic range when thinking about exposure length?
    Presumably we would want to have the brightest parts of each sun frame to be almost filling the full pixel depth, so maximising the dynamic range?
    This would then count against shorter exposures

    • @AstroWithRoRo
      @AstroWithRoRo  3 года назад

      Great question! You do need to worry about dynamic range, but in a different way. Usually the brightest part of any DSO image is the stars, once these saturate the pixels they are on, you have gathered all the light you can without beginning to lose DR in your image. However, this doesn't directly relate to exposure length. What matters for exposure length is how good each of those pixels are at converting photons to electrons in the sensor. The better the quantum efficiency of the camera, the faster it will gather signal, and therefore the faster the star pixels will fill up. High dynamic range simply allows the camera to more accurately save the differing levels of brightness in each individual pixel, going from completely white to completely black. How quickly your camera fully saturates is down to the QE of the sensor and how big the full well depth of each pixel is. A perfect camera would have 100% QE & a very big full well depth so you save all the photons, but don't over saturate your stars quickly, allowing the background nebulosity to collect lots of data.

  • @superearth5256
    @superearth5256 Год назад

    That means i dont need star tracker if i stack multiple short exposure images?

  • @ckott99
    @ckott99 2 года назад

    Thanks for some very helpful information. I usually go for 5 minute subs on clear nights, mostly to reduce disk storage requirements and computational power for stacking. However, when there are some fast moving clouds going through the sky, going to a shorter exposure subs would allow some data collection. My experience has been that at 5 minutes almost every exposure catches a cloud. It's good to know what my options are, and that I could go much lower and still have very acceptable results.

  • @Redpulsar2011
    @Redpulsar2011 3 года назад

    Thank you for your informations !

  • @heavyjohnny
    @heavyjohnny Год назад

    This is great info. But for me, IMO LOL, the right exp time depends on how long my mount will allow me to keep the shutter open before my stars turn into eggs. Provided of course my histogram is not clipping or I am not blowing out the stars. MORE DATA! MORE!!!!!!!!

  • @svenvanveen4160
    @svenvanveen4160 3 года назад

    Really interesting video! I saw that you recently got the 294mm pro and I also saw a red cat 51 on the mount. I am really interested in the deep sky performance of this camera with a wide field refractor, like the redcat, and especially how the 1x1 binning mode compares to 2x2 binning mode for deep sky imaging since there are some caveats with the 1x1 binning mode.

    • @AstroWithRoRo
      @AstroWithRoRo  3 года назад +1

      I am putting together a video about this exact subject (1x1 vs 2x2 binning with wide and narrow FoVs), I hope to get it finished within the next month so do stay tuned for that.

    • @svenvanveen4160
      @svenvanveen4160 3 года назад

      @@AstroWithRoRo Thanks for the quick reply. Subbed to the channel with notifications turned and looking forward to this video! Keep up the great work!

  • @haiderbhogadia4829
    @haiderbhogadia4829 Год назад

    Excellent many thanks

  • @Suhaib955
    @Suhaib955 2 года назад

    How can you manage dithering with short exposure lengths? Wouldn't you be loosing a lot of time in settling between the subs compared to longer exposure times?

    • @RobertKarlBerta
      @RobertKarlBerta Год назад

      Don't dither after every short exposure,....do it every three or more.

  • @mikemccann8822
    @mikemccann8822 3 года назад +1

    So, sharpcap has two tools, sensor analysis, and the brain feature found in the histogram tool. How do you correlate your formula with the results in this tool. I’m not as far as I would like with using it because along the process I discovered that my newt has light leaks. And winter has moved in with wind, rain, snow. But I’ll hopefully get back to it soon.

    • @Steve-br7wt
      @Steve-br7wt 3 года назад

      Yep, those tools work great with my refactor for sure.

    • @AstroWithRoRo
      @AstroWithRoRo  3 года назад +1

      This formula is actually the same that SharpCap Pro uses. It was created by Dr Robin Glover who is the creator of SharpCap :)

    • @mikemccann8822
      @mikemccann8822 3 года назад

      @@AstroWithRoRo so do you use the brain process to asses the night’s clarity, or do you use the formula and some other means to calculate that night’s image length.

    • @AstroWithRoRo
      @AstroWithRoRo  3 года назад

      I use NINA for my imaging, not SharpCap so I use the formula, keep minimum and maximum frame numbers in mind, and then take some educated guesses about the weather and seeing to come up with a sun time that I’m happy with. At home it’s usually quite short since I’m under heavy light pollution. If I head out to a dark site and the wind is calm then I start to let the minutes fly by for the subs.

  • @craigskinner8489
    @craigskinner8489 2 года назад

    Thank you. My next project is Sh2-192, Flying Bat. In order to capture the Squid portion in Oiii, I have settled on 8 min exposures. This is based on Dr Glover’s formulas. I am using a F5 refractor, QHY294m in 47 mode and 7 nm NB filters. My Bortal is 6. I have shot 5 min and 10 min in the past so will try 8 min this time. Planning on getting at least 30 hrs on Oiii so around 250 subs.
    Do you have thoughts on my reasoning?

    • @timbotron4000
      @timbotron4000 5 месяцев назад

      Did you finish this project?

  • @javierafeltra2840
    @javierafeltra2840 3 года назад

    Excellent video!! Congratulations!
    One conclusion about the video is that if we move from a zone of bortle 9 to one of bortle 2, the minimum subexp is prolonged. Especially if narrow band filters are used. In my case (ASI 294MC-Pro), using a Ha or SII filter in bortle 2 gives me a calculation of more than 600 seconds of minimum exposure time, making it very difficult to guide to reach those times.
    My question is: Is it correct to increase the gain (without losing so much dynamic range) to reduce the minimum exposure time in very little polluted skies?

    • @AstroWithRoRo
      @AstroWithRoRo  3 года назад +2

      You can increase the gain a bit if you're ok with the reduction in DR (say on really diffuse nebulae that don't have a lot of difference in their brightness). The numbers in this under dark skies may be "optimal" but certainly aren't the only number you can use. Even under dark skies, short exposures can work just fine, you will just end up with a bit more noise than if you could take those ultra long exposures. A 60s exposure in the city, and a 60s exposure under dark skies will still look WAY better under dark skies, so don't feel like it will not look good. It's just that under dark skies you can go for longer before the sky brightness overtakes the read noise, so the formula suggests you optimise for all the extra exposure time you can. The most important part though is to keep within your equipments means, pushing your equipment beyond their limits will mean you have to throw away more subs, making your image much worse than the extra read noise of shorter subs, even under dark skies.

  • @gregnicholl9011
    @gregnicholl9011 2 года назад

    G'day mate, nice video with good information. There is one thing missing however, something important. It was good of you to disclose that you have based this whole video on somebody else's hard work, but you really should mention Dr. Robin Glover by name & give him the credit he is due. And it's not too late to pin it up in a comment.

  • @geopolska
    @geopolska 2 года назад

    Good video, cheers.

  • @jaimie_t
    @jaimie_t 3 года назад

    I'm trying to use the sharpcap calculator referenced in the description (to compute P), but I don't know the "average" QE for my camera: ZWO ASI071MC Pro. The latest manual provides a QE "Peak" value of "TBD". I created a post on the ZWO forums to ask about this, but did not get an answer (a ZWO employee answered with some marketing language and a picture of the QE graph, but I don't know how to use that graph to compute the "average QE"). I wonder if a way exists to determine this by using the camera.

    • @AstroWithRoRo
      @AstroWithRoRo  3 года назад +1

      Using peak QE will give you a slightly shorter final exposure figure than average QE. I think for the 071MC you could use 40-45% QE as an average mark.

    • @jaimie_t
      @jaimie_t 3 года назад

      @@AstroWithRoRo Thank you!

  • @oM1naE
    @oM1naE 3 года назад

    I think there's something wrong with the very last calculation.
    It does not make sense that a Luminance frame has a longer minimum exposure time than RGB where only ~1/3 of the light is coming through the filter.

    • @AstroWithRoRo
      @AstroWithRoRo  3 года назад +1

      Yea you’re right. I got the RGB and L columns mixed up. L should be 1s and RGB should be 2s.

    • @brandonporter4227
      @brandonporter4227 2 года назад

      No, there's something seriously wrong with that calculation. I put in my numbers and I get a value of over 5000 seconds because my Sky Electron Rate comes out at a value of 0.01. My filters are 3nm, SQM is 21.4, f/4.9, QE 85%. My read noise is 2.25. So C*R^2/P is 10*2.25^/0.01 = 5065s. There's no way 5000 seconds is even close to accurate.

  • @arjundhannyify
    @arjundhannyify 2 года назад

    How about taking milkyway images?

  • @billallen275
    @billallen275 Год назад

    SImple - Tracking and Histogram, to start with, ISO, then light pollution... iteratively; that's how I see it as a process. Thank you.

  • @LM-ek2hb
    @LM-ek2hb 3 года назад

    Yes, - but how do I turn:
    "Sky Electron Rate 1.31 e/pixel/s"
    Into seconds of exposure??