Thanks for taking the time to do this experiment Luke. To me the 60s image looks just a fraction sharper, especially the stars. That could just be down to guiding error having more of an impact on the 300s subs as well as the stars starting to blow out in the longer subs. Given that I have always used 300s subs, this makes me think that for the f5.6 scope I am using, 60s to 120s subs would probably be every bit as good as 300s subs. Also the difference in SNR you pointed out is less than 1%, so not really worth worrying about. The only downside of shorter subs is that you end up with a lot more images to stack, but since I stack overnight while I sleep, not a worry for me. The advantage of more images is that you will have to throw away less time overall, due to satellites, cloud etc. What might make a good follow up experiment is to repeat this with narrowband filters on a nebula. Given the bandpass is so much smaller, perhaps there would be a much bigger difference (especially the Oiii channel on most targets).
Me too mate. My processing is pretty awful still after about 15 months of UK skies astro, so averaging around 1-2 clear night skies per month. I am getting better like, but when you see works produced by the likes of Luke, you feel lightyears behind! lol.
I am really enjoying your content Luke, as an old guy but a newbie in the hobby I always gain knowledge from watching your tests. I tend to stick with shorter subs as it's less painful to throw out a short sub due to a plane or satellite and clouds that come into view during exposure. I would really be interested in the narrow band duo filter test as I'm using a OSC camera and have only recently picked up some Askar C1 and C2 filters for my own testing. I'm still so new that most of what I'm doing is live stacking on the fly but saving the images for later processing. It's baby steps for me so that my brain can retain what I'm learning. Thanks Luke and all the best from SE Utah, Cheers !
At 9:45 you were examining some nebulae and commenting on a slight resolution win for the shorter sub. Immediately above and left of those three emission nebulae there is a dust lane that is substantially clearer in the short subs as well. I seem to see that all over the shorter sub images, actually, though without the ability to zoom in it's hard to be sure.
My happy-go-lucky strategy in moderately polluted skies is 30 sec sub exposures at f/5 - longer sub exposures are more blurry in my turbulent sky. Meet lots of headwind when talking lots of unguided short exposures... 😊
Hey Luke! I think the biggest benefit to using shorter subs is less reliance on your mount tracking accuracy and the ability to get more subs in less time to add to the averaging algo to help brings out more details. The only downside is some nebulosity is lost. For now I just make sure I am as close to the left side of the histogram without clipping. Thanks for the video mate!
Very good one! and quite surprised by the results! In this case it could be worth to go with 5 mins subs just to save space and computing time! I'll wait for the dual band tests! Keep up the good work! 👍👍
Fascinating. Over TH-cam, on my screen, I honestly could not tell the difference. The other advantage to shorter subs for my Bortle 6 sky is the prevalence of satellite and airplane trails. Shorter subs give me more subs without them. Also, everything I have read/been told says that shorter subs are needed in my light polluted skies because of unwanted light, even with filters. Now I need not worry about getting good quality with those shorter subs. But I'm still concentrating on fairly bright, fairly large objects right now. Will have to see if that changes with more difficult objects. Thanks for doing this, Luke.
Excellent test once again Luke. Nice to know there's a fairly wide range of acceptable exposures, and that going for shorter exposures to preserve star cores etc doesn't really hurt you.
Thanks Pete!! - agreed mate, I think the range of exposure lengths that stack with very high efficiency is pretty large, especially from my bright skies so read noise is always being swamped unless using super short exposures! Clear skies to you my friend :-D
Very interesting again, it's good to have tackled this believe into experiment! What this change for me is my pre-processing storage/capacity: I could actually have less, longer subs that would make my life so much easier. When you reach 20h of integration time, having 180s subs over 60s makes a big difference in storage !
Absolutely mate, yeah! 1200 subs vs 400, that's going to make a huge difference in processing time and storage consumption as you quite rightly say! 👍👍
In high Bortle areas, shooting short subs will add to your shot noise pretty quickly, though it should be partially compensated for in stacking with good dithering since 60s subs will give you more samples to average in the stacking process. Nonetheless, shot noise is a major troublemaker. Insofar as I understand it, to really benefit from very short subs, you need darker skies. I can only theorize the challenges of light pollution in processing, however, as I've never had to deal with it. As far as signal, that simply adds up. 60 1s subs will give as much signal as 1 60s sub. But the SNR will be different for a master derived from 60 1s subs than from 1 60s sub. 60 1s subs--higher shot noise but more samples to average out noise (less significant in dark skies), but your tracking/guiding errors will matter less and you can be more aggressive in culling subs. 1 60s sub, less shot noise. So a good strategy is that in high Bortle areas, shoot longer subs, though I generally find that you will always do as better to shoot as short as your conditions allow you get away with.
Unless you're sick of this experiment... I'd like to see the dual narrowband with one shot color and about f7 results (simply because that's what I have and I'm selfish... 😜) So far the differences seem to be a wash to my eyes but then they're old, less experienced in pixel peeping and not to be trusted... This experiment so far seems to be blowing most of the common knowledge carried over from back in the dark ages right out of the water! Thanks for all the hard work, Luke! 👍👍
One not minor advantage of the longer exposures is reducing the amount of subs, 5x reduction in this case. With my setup, I'm limited to 30" subs (intervalometer in the mail...). That means that I stacked 840 subs for a 7-hour integration, taking over 500 GB of working space and 7+ hours of WBPP time, on a decent computer... I want longer exposures just to be able to process more quickly and efficiently.
The real benefit of shorter subs is in satellite and cloud loss of data. Lose 60 seconds or 5 minutes. So being so very close in quality the same time of opportunity to shoot with say 10 frames lost to whatever yields more data with shorter frames.
Thanks Luke, this series is a huge help for lots of us. I would love to see the same experiment at medium focals (f4 or f5) with a narrowband like the L-ultimate 🌌🔭
Hey Luke, thank you for keeping this video series going, loving it so far ! Could you maybe provide raw data for this one, as youtube compression makes it hard seeing little differences in details (maybe thats the whole point though, exposure length doesn't matter xD) Clear skies, mate, keep doing what you are doing, appreciate it very much !
Hey mate! - Thanks so much for watching! I'm currently running rather low on cloud storage so can't easily make this available (yet) I'm going to take a good look through and clear out what I can after the weekend though, so hopefully more room then - if you're really interested in seeing it I can make it available then? Cheers!
Great video. One thing I wonder about is why you don't let your exposure length be dictated by the amount of overexposed pixels? Judging by the unstretched 300s sub, there are many overexposed pixels. Shouldn't the goal be to keep those to just a few hundred? You can actually see that the galaxy core in the 60s sub is better defined.
Hi luke thanks for continuing with this experiment mate. I cant believe how similar the results are , the only downside i can see is the number of files to stack with the short exposures , Thanks again for taking the time to make these video mate
Thanks Tony!! - I really expected to see a little more difference than this too, but it's pretty much identical isn't it, just really minor differences! :-)
Brilliant video Luke. Many thanks for doing the experiments and sharing your results. It really is interesting how little difference there is. Thanks for all your hard work.
I am in a Bortle 6 area. My go to exposure length is 180 seconds. To me, this is the sweet spot. If I get wind shake, I’ve blown a 3 minute sub vs losing 5 minutes with 5 min subs. 1 min subs are ‘OK’ but take up a lot of room with long exposures. I save my 30 sec-1 min subs for comets.
Thanks so much for going through this Luke! I also often pondered the differences between the two sets of exposures and it seems like it really does not make much of a difference here. I look forward to the Dual Narrowband version of this with the Askar 120 APO at F7 especially on something that is really faint and barely or does not show up in the subframes but does when you do a final integration.
This rocks, Luke. Thanks for the continued research into this topic. These data align closely with my ED127 setup...except for my old camera. It's great to see what you learned. Cheers!
Great to see these results! I don't have a guided scope and my mount's tracking is far from perfect, so I can't take really long exposures. It's good to see that I can get enough data for a decent picture with shorter exposures
Another really interesting comparison Luke. I definitely think there's not a great deal of difference with bright targets. However I suspect long exposures would have better results with fainter targets ? Always a great watch mate 👍
Thanks Pete mate! - It's going to be interesting to test again on a narrowband target and see how that turns out too, RE: fainter targets, the SNR difference on the fainter regions of this image are very small it seems, so maybe the difference won't be too big after all! :-D Clear skies my friend!
You briefly metioned this in the video but by adjusting the gain on the shorter exposure image you would have most likely matched the brightness of the longer one as gain and exposure length work together. I'm sure you're well aware of Robin Glover's calculations for setting gain/exposure so a test using those calculation and adjusting both variables woud be intresteing if you're wanting to do another experement.
As an astrophotographer brought up in the Cuiv (i.e. lazy) school of astrophotography i really appreciate you doing the hard work for me. Would be interested in seeing if using something like a dual band filter with its better SNR would change the results?
I think it will change the results for sure, I can't wait to see what that actually looks like in practice though! :-) Further tests coming, Clear skies!
Awesome results Luke. I am considering moving to 120APO instead of an F5 8” reflector and was concerned about working with F7 at native FL but your results have shown that this may not be a big issue.
Hey mate!! - I think you're right - you'll see a difference on your exposures for sure, but it's probably not going to be night-and-day dramatic in terms of light loss! :-) Clear skies!
I have a Skywatcher 200pds and I was thinking of buying an askar reflector too. But I was considering the 103 with X1 flattener, .8 and .6 reducers to have a variety of setups and try something very different from what I have. Are you using a colour or mono camera?
Great video. I am relatively new to astrophotography and this video will help in determining exposure time. To my eye the 60s image was slightly sharper. I am also shooting in light polluted skies at Bortle 8. I will try a similar experiment with my equipment and see how that turns out.
Thanks Luke for this follow up video. It’s such a pleasure to learn from your analysis (and labor) putting this together. With Nebula season approaching, please consider doing a comparison video on narrow band. I’ve typically been doing 5 minute NB subs (Bortle 7-8) and was thinking of jumping to 10 minute subs. Would love to hear your thoughts on NB.
Another interesting result mate I'm thinking about having another go at this target weekend at Nicky's so I'll probably go to 180 seconds just to see what I can get, clear skies mate.
Luke to my eye, the 60sec subs on the left near the beginning actually looked a teeny tiny bit better? Interesting! If I may, would you say it's advantageous to use a super fast F-ratio under city night skies? I always assumed F4, F3 or as low as F2 would actually be worse because it would soak up much more light pollution? I currently go no faster than F5 with my 8" Newt. reflector? Am I mistaken Luke? ( Sorry, I appreciate you have lots of comments to read n respond to! ) BTW awesome vid as always thanks Luke, you're very easy to listen to and you come across as very intelligent!
Thanks ever so much for sharing your thoughts my friend!! It's appreciated 👍 Re: faster f/ratios, - generally speaking they catch more of everything, light pollution and signal, luckily for us the target signal stacks up linearly over time with more and more subs, but the noise sources don't stack linearly, so as long as you keep gathering subs your signal will pull away from the noise over time, and it'll happen faster with a faster f-ratio (again, generally speaking!) Thanks again mate! 👍👍
Very interesting results, I like your so-called interleaved capture method. I assume that you are using WBPP to do the stacking, and the same 'Integration Parameters' and 'Subframe Weighting Formulas' for both long and short subs. Is it possible that the 'Subframe Weighting Formula' being used is more suited to fewer long subs than many shorter ones. I suspect that this could end up as a real rabbit hole 😉
Absolutely agree this could become a rabbit hole haha :-D I did the stacking in APP as it happens, settings were kept identical between them :-) Hope that helps!!
Hey Luke my new goto exposure is 120 in narrowband rgb. Any more and the background mean rockets. Added bonus is i find more resolution with 120 secs opposed to 300secs. Maybe seeing has more effect on longer subs. Great video mate and clear skies.
Another great video! One question I had is whether taking more photos for shorter times has a benefit of allowing one to retain more "excellent" image time. I always find that a certain percent of images are slightly flawed (e.g., egg-shaped stars from tracking errors). I get better a better final image by discarding these prior to stacking (I think correcting these in post doesn't do as good a job). If I took 5 one-minute photos, perhaps I would lose 1 out of five (retaining 4 minutes out of five). On the other hand, if that one minute was part of a 5 minute photo it might result in losing the whole 5 minute image. In other words, taking 1 minute photos allows for greater control over what makes the final cut in a manner that retains the maximum amount of "excellent" image time and hence the possibility of creating a superior final image. Thoughts?
I think that's spot-on mate, having the ability to be ruthless when culling bad subs because you're overall only losing a minute of data per rejected sub is absolutely a boon, both in final quality of the stack and also raw SNR! :-) throwing away a 10m sub because a momentary gust of wind/small passing cloud happened and spoiled the whole thing feels baaaad!! - with 1m subs you could throw the 1 or 2 bad frames and keep the rest, boosting overall snr as you quite rightly say!
Funny ... In the first video of the series, I told you that after several tests i decided to ALWAYS stick to the 2min subs ( bortle 5, touptek imx 571 OSC camera) as I could not see any advantage on going beyond 2 that. Now, after the third test of extensive analysis you said "somewhere between 1 and 5 mins". 🤣 It looks to me we converged to the same conclusion ( perhaps because we have a similar bortle and same camera sensor) .
Feels like a natural conclusion to make yeah! :-D I've had fun with these tests so far, I think the f7 narrowband/dual narrowband test will finally show some differences though, or at least I imagine so! Clear skies! :-D
Fascinating experiment, and it seemed to me that the 60s result had slightly higher contrast than the 300s. However, I would be interested to know if you used the same gain settings for the two sets and if not just how much did you up the gain for the 60s subs. Anyway, great test, thanks for doing it.
Hey there mate! - I actually kept the gain settings the same for both exposures here, just as the default 'HCG open' mode - I did consider trying to normalise the sub exposure captures slightly by elevating the 60s subs gain, but decided to just leave it after early test exposures looked fine in both cases :-) Cheers!
@@lukomatico Hi Luke, that is really useful. I've been getting rather too many bloated stars with my 300s subs (at f7, gain 180 using an ASI533MC). Tried 200s subs last night on M84, less bloated stars but detail of the spiral arms still came through. Win.
Hello Luke. New subscriber here. Just wanted to say hello and to thank you sincerely for your awesome videos and for all your time & effort ! I recently moved from a modified 6D to a ASI6200MC Pro for my TEC140 (F/7) along with using PI & PS for my processing. My God what a difference !!!! Your videos have helped me greatly. I have settled on 120 sec or 150 sec unguided subs for my Bortle 5 skies. My greatest uncertainty at this point is knowing what gain to use. I typically use 100 (for max dynamic range) which I hope is helping me not blow out brighter stars or bright cores. I would love to see a future video discussing the determination of the best gain for different setups & scenarios. Am I losing out by shooting at G100 with my short exposure times vs. using a gain of say 200 or even 300? TU again !
Hey there!! - Thank you so much for your support, that means a lot my friend! :-D Congratulations on the new camera and for pairing it with such a lovely scope! - RE: your question about gain, I'd use the 6200 at the HCG open setting just as you have been doing, gain 100! :-) Going from 100 up-to 300 or even beyond in most situations will not offer much 'gain' in image quality, if you'll excuse the pun! rather, it can simply make matters worse with the reduction in available dynamic range. I hope that helps! Luke
@@lukomatico Hi Luke, sure does help, thank you for the advice. I seem to have a hard time maintaining my star colors which is why I have been using G100 but my histogram is too far to the left I suspect. Although in the end, after processing I am able to make a not so horrible image :-) Tonight I go after the Pelican....cross your fingers for me ! TU agn. Gedas
Actually you should do the same test with a camera with a lower Qe (the 585 is around 90%), with something like around 70%, maybe 60%, the difference should be more visible.
Hey mate! - I've got my RASA narrowband long vs short test video up already, but need some clear skies to check with the slower scope :-) I expect we'll see more of a difference then! Clear skies!
Ah yea I saw that one, I look forward to the next test. I've narrowed my kit down to a 250 quattro and a 6" hyperstar so these videos are very interesting to me. After watching your first one with the 10 min subs vs 1 min I had a clear night not long after and tried out the 1m subs with my 250 on the iris and it was amazing how many subs I had at the end, I'm used to imaging at either 300s or 420s so only getting about 19 images a night haha
I'd love to mate,it's just these shorts nights and now no astronomical darkness at this time of year limits what's reasonably possible :-) I'd add RE: fainter targets, the SNR difference on the fainter regions of this image (wispy extensions, background galaxies) are very small it seems, so maybe the difference won't be too big after all! :-D
@@lukomatico I hear you!! The clouds the last couple of years have been smothering for this hobby. I'd love to test these things too but man if I get a clear night I am after an image vs testing!! Love the material.. thanks for your videos... they are great!!
Hi Luke, I settled on -10C 100gain 120sec L-eNhance for *everything* with my 533mc on a 130APO (732mm) in Bortle 7 skies. It gives massive advantages to habitually do the same thing every night. This strongly manages the risk of screwing up. Given the large number of guiding parameters and setup conditions and preparation steps you need to attend to, my own experience included a lot of repeat failures to capture any usable data in back to back sessions. What your tests show it that yes indeed it doesn't matter much at all 👍. I've also learned that changing settings (within reason) has a *tiny* effect compared with the variation I (Mr average PI afficionado) introduce with my best processing efforts, and I suspect that this in turn has a *tiny* effect compared with the seeing and dark sky conditions you can get with travelling. Finally the whole thing is dominated by the total integration time. So thanks for this confirmation!
Thank you for watching my friend!! - I think that's a real quality set of observations and thoughts, thank you for sharing! :-D Looking forwards to the narrowband/dual narrowband test now, that should finally show some larger differences (I think!)
Hi Luke! I can't remember how bright are your skies? I live just outside of Toronto and have wondered how long an exposure I can try. I'm using 20s but maybe I should try longer exposures. I have a Gear60 f/5 scope and a Player One Neptune CII. I've ordered an Ares-C will that change things?
Hey mate! My skies are bortle 7 here :-) Congratulations on the new camera by the way! That'll allow you to get brighter and better signal images for any given exposure time when vs the Neptune 👍
@@lukomatico Last night I finally got auto focussing working. I think that's a game changer for sure. Everything after that like polar alignment and just peace of mind will make this easier. Never realized that the number of steps is so small. If you had told me the total number of steps for a run was 800 steps of 1.3 microns I might not have believed it.
Hey Andy! - I didn't measure them exactly but the 18 stack was definitely quicker, however both were quite fast overall, my pc is pretty quick though - with a larger megapixel camera it would probably be a drag stacking hundreds!
I don't think you mentioned your Bortle zone. This is an interesting video as I have just bought a 10 Mircon mount and the consensus is guiding isn't needed for around five minutes or less depending on your model created for the mount and the focal length of your scope. If I can get away from the need to guide at say 1645 mm, I would be happy for shorter exposures. The test will be for F10 and 3 nm narrowband filters. Our skies here have been rubbish for nearly four years so I rarely take the opportunity to experiment with exposures. On a completely off topic note, I did narrowband exposures of a planetary nebula (PK 294-0.1 near the Running Chicken Nebula) at 645 mm (refractor @ F5.6) and at 2350 mm (reflector @ F10) and after cropping the refractor image, I couldn't see much difference between the two. It made me wonder why I bothered with the reflector considering how small the target was. Perhaps you might want to do something similar.
I use 5 to 8 seond exposures in Sharp Cap unless I am using a dual band filter, when I go to 15 seonds. I never try using 1 to 5 minute exposures. I bore easily, while waiting for the next update.
Thanks Luke, taking into consideration how many subs I bin, it's shorter subs all the way from now on. This will no doubt result in more integration time per session. Again thank you for an unbiased test.
You are true and false at one moment. The main reason to use long subs is to catch dust + faintly visible details. For example you can`t use 60s subs on Iris nebula, just try. If your sky is not excellent and you are near the town - all details will be mixed with light noise. Also you can`t use short exposures with narrowband, the signal will not be enough. P.S. I don`t know about you but I see difference in dust areas on your M51 (top-right corner). 300s catched more, and if you take more subs you better see this difference. Thx.
Thanks for taking the time to do this experiment Luke. To me the 60s image looks just a fraction sharper, especially the stars. That could just be down to guiding error having more of an impact on the 300s subs as well as the stars starting to blow out in the longer subs. Given that I have always used 300s subs, this makes me think that for the f5.6 scope I am using, 60s to 120s subs would probably be every bit as good as 300s subs. Also the difference in SNR you pointed out is less than 1%, so not really worth worrying about. The only downside of shorter subs is that you end up with a lot more images to stack, but since I stack overnight while I sleep, not a worry for me. The advantage of more images is that you will have to throw away less time overall, due to satellites, cloud etc. What might make a good follow up experiment is to repeat this with narrowband filters on a nebula. Given the bandpass is so much smaller, perhaps there would be a much bigger difference (especially the Oiii channel on most targets).
I think that's a really reasonable set of conclusions my friend, thank you for sharing!! - I hope to do more tests for sure :-)
Clear skies!
Your 90 minute stack at F7 looks worlds better than my 6 hour stack at F5.5. I have such a far way to go in this hobby.
Me too mate. My processing is pretty awful still after about 15 months of UK skies astro, so averaging around 1-2 clear night skies per month. I am getting better like, but when you see works produced by the likes of Luke, you feel lightyears behind! lol.
I feel you buddy...
I love this hobby, clear skies to you all!
I am really enjoying your content Luke, as an old guy but a newbie in the hobby I always gain knowledge from watching your tests. I tend to stick with shorter subs as it's less painful to throw out a short sub due to a plane or satellite and clouds that come into view during exposure. I would really be interested in the narrow band duo filter test as I'm using a OSC camera and have only recently picked up some Askar C1 and C2 filters for my own testing. I'm still so new that most of what I'm doing is live stacking on the fly but saving the images for later processing. It's baby steps for me so that my brain can retain what I'm learning. Thanks Luke and all the best from SE Utah, Cheers !
Thank you so much for watching!! :-)
At 9:45 you were examining some nebulae and commenting on a slight resolution win for the shorter sub. Immediately above and left of those three emission nebulae there is a dust lane that is substantially clearer in the short subs as well. I seem to see that all over the shorter sub images, actually, though without the ability to zoom in it's hard to be sure.
My happy-go-lucky strategy in moderately polluted skies is 30 sec sub exposures at f/5 - longer sub exposures are more blurry in my turbulent sky. Meet lots of headwind when talking lots of unguided short exposures... 😊
Hey Luke! I think the biggest benefit to using shorter subs is less reliance on your mount tracking accuracy and the ability to get more subs in less time to add to the averaging algo to help brings out more details. The only downside is some nebulosity is lost. For now I just make sure I am as close to the left side of the histogram without clipping. Thanks for the video mate!
Very good one! and quite surprised by the results! In this case it could be worth to go with 5 mins subs just to save space and computing time! I'll wait for the dual band tests! Keep up the good work! 👍👍
Grazie Luke. all your efforts and sharing of your experiences are a valuable source of information. For me, you are a true reference
That's so kind of you my friend, thank you very much indeed for your support! :-) Clear skies to you!!
Fascinating. Over TH-cam, on my screen, I honestly could not tell the difference. The other advantage to shorter subs for my Bortle 6 sky is the prevalence of satellite and airplane trails. Shorter subs give me more subs without them. Also, everything I have read/been told says that shorter subs are needed in my light polluted skies because of unwanted light, even with filters. Now I need not worry about getting good quality with those shorter subs. But I'm still concentrating on fairly bright, fairly large objects right now. Will have to see if that changes with more difficult objects. Thanks for doing this, Luke.
Excellent test once again Luke. Nice to know there's a fairly wide range of acceptable exposures, and that going for shorter exposures to preserve star cores etc doesn't really hurt you.
Thanks Pete!! - agreed mate, I think the range of exposure lengths that stack with very high efficiency is pretty large, especially from my bright skies so read noise is always being swamped unless using super short exposures!
Clear skies to you my friend :-D
Very interesting again, it's good to have tackled this believe into experiment! What this change for me is my pre-processing storage/capacity: I could actually have less, longer subs that would make my life so much easier. When you reach 20h of integration time, having 180s subs over 60s makes a big difference in storage !
Absolutely mate, yeah! 1200 subs vs 400, that's going to make a huge difference in processing time and storage consumption as you quite rightly say! 👍👍
In high Bortle areas, shooting short subs will add to your shot noise pretty quickly, though it should be partially compensated for in stacking with good dithering since 60s subs will give you more samples to average in the stacking process. Nonetheless, shot noise is a major troublemaker. Insofar as I understand it, to really benefit from very short subs, you need darker skies. I can only theorize the challenges of light pollution in processing, however, as I've never had to deal with it. As far as signal, that simply adds up. 60 1s subs will give as much signal as 1 60s sub. But the SNR will be different for a master derived from 60 1s subs than from 1 60s sub. 60 1s subs--higher shot noise but more samples to average out noise (less significant in dark skies), but your tracking/guiding errors will matter less and you can be more aggressive in culling subs. 1 60s sub, less shot noise. So a good strategy is that in high Bortle areas, shoot longer subs, though I generally find that you will always do as better to shoot as short as your conditions allow you get away with.
Unless you're sick of this experiment... I'd like to see the dual narrowband with one shot color and about f7 results (simply because that's what I have and I'm selfish... 😜) So far the differences seem to be a wash to my eyes but then they're old, less experienced in pixel peeping and not to be trusted... This experiment so far seems to be blowing most of the common knowledge carried over from back in the dark ages right out of the water! Thanks for all the hard work, Luke! 👍👍
Oh my pleasure mate, thank you ever so much for watching!! :-D
I'll certainly get that next comparison done as soon as possible 👍👍
you should do a linear fit on both images, then apply the same processes to each image. I feel like tjat would give a good comparison
One not minor advantage of the longer exposures is reducing the amount of subs, 5x reduction in this case.
With my setup, I'm limited to 30" subs (intervalometer in the mail...). That means that I stacked 840 subs for a 7-hour integration, taking over 500 GB of working space and 7+ hours of WBPP time, on a decent computer... I want longer exposures just to be able to process more quickly and efficiently.
That's definitely something that needs consideration my friend!! :-) Clear skies to you!
The real benefit of shorter subs is in satellite and cloud loss of data. Lose 60 seconds or 5 minutes. So being so very close in quality the same time of opportunity to shoot with say 10 frames lost to whatever yields more data with shorter frames.
Thanks Luke, this series is a huge help for lots of us.
I would love to see the same experiment at medium focals (f4 or f5) with a narrowband like the L-ultimate 🌌🔭
Great suggestion!
Hey Luke, thank you for keeping this video series going, loving it so far ! Could you maybe provide raw data for this one, as youtube compression makes it hard seeing little differences in details (maybe thats the whole point though, exposure length doesn't matter xD) Clear skies, mate, keep doing what you are doing, appreciate it very much !
Hey mate! - Thanks so much for watching! I'm currently running rather low on cloud storage so can't easily make this available (yet) I'm going to take a good look through and clear out what I can after the weekend though, so hopefully more room then - if you're really interested in seeing it I can make it available then?
Cheers!
Great video. One thing I wonder about is why you don't let your exposure length be dictated by the amount of overexposed pixels?
Judging by the unstretched 300s sub, there are many overexposed pixels. Shouldn't the goal be to keep those to just a few hundred?
You can actually see that the galaxy core in the 60s sub is better defined.
Really just a by-product of the test variables my friend, normally I'd try to avoid burnout like that :-) Cheers!
Hi luke thanks for continuing with this experiment mate. I cant believe how similar the results are , the only downside i can see is the number of files to stack with the short exposures , Thanks again for taking the time to make these video mate
Thanks Tony!! - I really expected to see a little more difference than this too, but it's pretty much identical isn't it, just really minor differences! :-)
Great video, Luke. Please do make the narrowband and the duo narrowband video. It would be very helpful!
Will do! Thank you so much! :-D
Brilliant video Luke. Many thanks for doing the experiments and sharing your results. It really is interesting how little difference there is. Thanks for all your hard work.
My pleasure mate!! thanks ever so much for watching :-) Clear skies!
I am in a Bortle 6 area. My go to exposure length is 180 seconds. To me, this is the sweet spot. If I get wind shake, I’ve blown a 3 minute sub vs losing 5 minutes with 5 min subs. 1 min subs are ‘OK’ but take up a lot of room with long exposures. I save my 30 sec-1 min subs for comets.
That's a wise move mate yeah! it's less of a loss when those unavoidable lost subs come around! (wind/passing cloud etc)
Thanks so much for going through this Luke! I also often pondered the differences between the two sets of exposures and it seems like it really does not make much of a difference here. I look forward to the Dual Narrowband version of this with the Askar 120 APO at F7 especially on something that is really faint and barely or does not show up in the subframes but does when you do a final integration.
My pleasure mate!! So glad you've found some enjoyment from these videos :-) it's a lot of fun to make them and a real privilege to share them! 👍👍
This rocks, Luke. Thanks for the continued research into this topic. These data align closely with my ED127 setup...except for my old camera. It's great to see what you learned. Cheers!
Great to hear! Thank you ever so much my friend
Great to see these results! I don't have a guided scope and my mount's tracking is far from perfect, so I can't take really long exposures. It's good to see that I can get enough data for a decent picture with shorter exposures
Glad to help mate!! that sounds like sticking with shorter subs is absolutely the right move for your rig right now :-)
Another really interesting comparison Luke. I definitely think there's not a great deal of difference with bright targets. However I suspect long exposures would have better results with fainter targets ? Always a great watch mate 👍
Thanks Pete mate! - It's going to be interesting to test again on a narrowband target and see how that turns out too, RE: fainter targets, the SNR difference on the fainter regions of this image are very small it seems, so maybe the difference won't be too big after all! :-D
Clear skies my friend!
You briefly metioned this in the video but by adjusting the gain on the shorter exposure image you would have most likely matched the brightness of the longer one as gain and exposure length work together.
I'm sure you're well aware of Robin Glover's calculations for setting gain/exposure so a test using those calculation and adjusting both variables woud be intresteing if you're wanting to do another experement.
As an astrophotographer brought up in the Cuiv (i.e. lazy) school of astrophotography i really appreciate you doing the hard work for me.
Would be interested in seeing if using something like a dual band filter with its better SNR would change the results?
I think it will change the results for sure, I can't wait to see what that actually looks like in practice though! :-) Further tests coming, Clear skies!
Awesome results Luke.
I am considering moving to 120APO instead of an F5 8” reflector and was concerned about working with F7 at native FL but your results have shown that this may not be a big issue.
Hey mate!! - I think you're right - you'll see a difference on your exposures for sure, but it's probably not going to be night-and-day dramatic in terms of light loss! :-)
Clear skies!
@@lukomatico The ASKAR looks like a great piece of kit and the ease of use versus a reflector is tempting.
I have a Skywatcher 200pds and I was thinking of buying an askar reflector too.
But I was considering the 103 with X1 flattener, .8 and .6 reducers to have a variety of setups and try something very different from what I have.
Are you using a colour or mono camera?
Great video. I am relatively new to astrophotography and this video will help in determining exposure time. To my eye the 60s image was slightly sharper. I am also shooting in light polluted skies at Bortle 8. I will try a similar experiment with my equipment and see how that turns out.
Excellent!! I'd be interested to hear how your own experiment goes my friend :-D
Thanks Luke for this follow up video. It’s such a pleasure to learn from your analysis (and labor) putting this together. With Nebula season approaching, please consider doing a comparison video on narrow band. I’ve typically been doing 5 minute NB subs (Bortle 7-8) and was thinking of jumping to 10 minute subs. Would love to hear your thoughts on NB.
Glad you enjoyed it Joe my friend, and those extra tests will be coming for sure! :-)
Another interesting result mate I'm thinking about having another go at this target weekend at Nicky's so I'll probably go to 180 seconds just to see what I can get, clear skies mate.
Clear skies mate!! :-)
Luke to my eye, the 60sec subs on the left near the beginning actually looked a teeny tiny bit better? Interesting!
If I may, would you say it's advantageous to use a super fast F-ratio under city night skies? I always assumed F4, F3 or as low as F2 would actually be worse because it would soak up much more light pollution? I currently go no faster than F5 with my 8" Newt. reflector? Am I mistaken Luke? ( Sorry, I appreciate you have lots of comments to read n respond to! )
BTW awesome vid as always thanks Luke, you're very easy to listen to and you come across as very intelligent!
Thanks ever so much for sharing your thoughts my friend!! It's appreciated 👍
Re: faster f/ratios, - generally speaking they catch more of everything, light pollution and signal, luckily for us the target signal stacks up linearly over time with more and more subs, but the noise sources don't stack linearly, so as long as you keep gathering subs your signal will pull away from the noise over time, and it'll happen faster with a faster f-ratio (again, generally speaking!)
Thanks again mate! 👍👍
@@lukomatico Thanks so much for explaining that Luke! Really appreciate it mate! 🙂👍
Very interesting Luke, thanks for doing this ….👍🏻
My pleasure mate!!
Very interesting results, I like your so-called interleaved capture method. I assume that you are using WBPP to do the stacking, and the same 'Integration Parameters' and 'Subframe Weighting Formulas' for both long and short subs. Is it possible that the 'Subframe Weighting Formula' being used is more suited to fewer long subs than many shorter ones. I suspect that this could end up as a real rabbit hole 😉
Absolutely agree this could become a rabbit hole haha :-D I did the stacking in APP as it happens, settings were kept identical between them :-) Hope that helps!!
More good observational data to help people image, well done mate !
Damo
Thank you so much mate!! :-) That means a lot!
Hey Luke my new goto exposure is 120 in narrowband rgb. Any more and the background mean rockets. Added bonus is i find more resolution with 120 secs opposed to 300secs. Maybe seeing has more effect on longer subs. Great video mate and clear skies.
That sounds like it's working out nicely!! - Clear skies Rob my friend!!
Great comparison Luke. How often did you dither for the 60 seconds and the 300 seconds?
Thank you!! - the 300s subs were dithered every sub, the 60s subs were dithered every five subs :-)
Thats an awesome scope your using boss and the tests are outstanding.. but what about 5x120 vs 2x300 - only joking, thanks for your hard work Luke
Thank you so much mate! :-D
Another great video! One question I had is whether taking more photos for shorter times has a benefit of allowing one to retain more "excellent" image time. I always find that a certain percent of images are slightly flawed (e.g., egg-shaped stars from tracking errors). I get better a better final image by discarding these prior to stacking (I think correcting these in post doesn't do as good a job). If I took 5 one-minute photos, perhaps I would lose 1 out of five (retaining 4 minutes out of five). On the other hand, if that one minute was part of a 5 minute photo it might result in losing the whole 5 minute image. In other words, taking 1 minute photos allows for greater control over what makes the final cut in a manner that retains the maximum amount of "excellent" image time and hence the possibility of creating a superior final image. Thoughts?
I think that's spot-on mate, having the ability to be ruthless when culling bad subs because you're overall only losing a minute of data per rejected sub is absolutely a boon, both in final quality of the stack and also raw SNR! :-) throwing away a 10m sub because a momentary gust of wind/small passing cloud happened and spoiled the whole thing feels baaaad!! - with 1m subs you could throw the 1 or 2 bad frames and keep the rest, boosting overall snr as you quite rightly say!
Funny ... In the first video of the series, I told you that after several tests i decided to ALWAYS stick to the 2min subs ( bortle 5, touptek imx 571 OSC camera) as I could not see any advantage on going beyond 2 that. Now, after the third test of extensive analysis you said "somewhere between 1 and 5 mins". 🤣
It looks to me we converged to the same conclusion ( perhaps because we have a similar bortle and same camera sensor) .
Feels like a natural conclusion to make yeah! :-D I've had fun with these tests so far, I think the f7 narrowband/dual narrowband test will finally show some differences though, or at least I imagine so!
Clear skies! :-D
Fascinating experiment, and it seemed to me that the 60s result had slightly higher contrast than the 300s. However, I would be interested to know if you used the same gain settings for the two sets and if not just how much did you up the gain for the 60s subs.
Anyway, great test, thanks for doing it.
Hey there mate! - I actually kept the gain settings the same for both exposures here, just as the default 'HCG open' mode - I did consider trying to normalise the sub exposure captures slightly by elevating the 60s subs gain, but decided to just leave it after early test exposures looked fine in both cases :-) Cheers!
@@lukomatico Hi Luke, that is really useful. I've been getting rather too many bloated stars with my 300s subs (at f7, gain 180 using an ASI533MC). Tried 200s subs last night on M84, less bloated stars but detail of the spiral arms still came through. Win.
Hello Luke. New subscriber here. Just wanted to say hello and to thank you sincerely for your awesome videos and for all your time & effort ! I recently moved from a modified 6D to a ASI6200MC Pro for my TEC140 (F/7) along with using PI & PS for my processing. My God what a difference !!!! Your videos have helped me greatly. I have settled on 120 sec or 150 sec unguided subs for my Bortle 5 skies. My greatest uncertainty at this point is knowing what gain to use. I typically use 100 (for max dynamic range) which I hope is helping me not blow out brighter stars or bright cores. I would love to see a future video discussing the determination of the best gain for different setups & scenarios. Am I losing out by shooting at G100 with my short exposure times vs. using a gain of say 200 or even 300? TU again !
Hey there!! - Thank you so much for your support, that means a lot my friend! :-D
Congratulations on the new camera and for pairing it with such a lovely scope! - RE: your question about gain, I'd use the 6200 at the HCG open setting just as you have been doing, gain 100! :-) Going from 100 up-to 300 or even beyond in most situations will not offer much 'gain' in image quality, if you'll excuse the pun! rather, it can simply make matters worse with the reduction in available dynamic range.
I hope that helps!
Luke
@@lukomatico Hi Luke, sure does help, thank you for the advice. I seem to have a hard time maintaining my star colors which is why I have been using G100 but my histogram is too far to the left I suspect. Although in the end, after processing I am able to make a not so horrible image :-) Tonight I go after the Pelican....cross your fingers for me ! TU agn. Gedas
Actually you should do the same test with a camera with a lower Qe (the 585 is around 90%), with something like around 70%, maybe 60%, the difference should be more visible.
Thanks for an amazing video :) it's completely changed how I image. Have you done one for narrowband?
Hey mate! - I've got my RASA narrowband long vs short test video up already, but need some clear skies to check with the slower scope :-) I expect we'll see more of a difference then!
Clear skies!
Ah yea I saw that one, I look forward to the next test. I've narrowed my kit down to a 250 quattro and a 6" hyperstar so these videos are very interesting to me. After watching your first one with the 10 min subs vs 1 min I had a clear night not long after and tried out the 1m subs with my 250 on the iris and it was amazing how many subs I had at the end, I'm used to imaging at either 300s or 420s so only getting about 19 images a night haha
Maybe you should try a more faint subject so the difference in the exposure times as it relates to brightness and detail will be emphasized...
I'd love to mate,it's just these shorts nights and now no astronomical darkness at this time of year limits what's reasonably possible :-)
I'd add RE: fainter targets, the SNR difference on the fainter regions of this image (wispy extensions, background galaxies) are very small it seems, so maybe the difference won't be too big after all! :-D
@@lukomatico I hear you!! The clouds the last couple of years have been smothering for this hobby. I'd love to test these things too but man if I get a clear night I am after an image vs testing!! Love the material.. thanks for your videos... they are great!!
Hi Luke, I settled on -10C 100gain 120sec L-eNhance for *everything* with my 533mc on a 130APO (732mm) in Bortle 7 skies. It gives massive advantages to habitually do the same thing every night. This strongly manages the risk of screwing up. Given the large number of guiding parameters and setup conditions and preparation steps you need to attend to, my own experience included a lot of repeat failures to capture any usable data in back to back sessions. What your tests show it that yes indeed it doesn't matter much at all 👍. I've also learned that changing settings (within reason) has a *tiny* effect compared with the variation I (Mr average PI afficionado) introduce with my best processing efforts, and I suspect that this in turn has a *tiny* effect compared with the seeing and dark sky conditions you can get with travelling. Finally the whole thing is dominated by the total integration time. So thanks for this confirmation!
Thank you for watching my friend!! - I think that's a real quality set of observations and thoughts, thank you for sharing! :-D
Looking forwards to the narrowband/dual narrowband test now, that should finally show some larger differences (I think!)
Hi Luke! I can't remember how bright are your skies? I live just outside of Toronto and have wondered how long an exposure I can try. I'm using 20s but maybe I should try longer exposures. I have a Gear60 f/5 scope and a Player One Neptune CII. I've ordered an Ares-C will that change things?
Hey mate!
My skies are bortle 7 here :-)
Congratulations on the new camera by the way! That'll allow you to get brighter and better signal images for any given exposure time when vs the Neptune 👍
@@lukomatico Last night I finally got auto focussing working. I think that's a game changer for sure. Everything after that like polar alignment and just peace of mind will make this easier. Never realized that the number of steps is so small. If you had told me the total number of steps for a run was 800 steps of 1.3 microns I might not have believed it.
Thanks for the Video, Luke... was there a significant difference it stacking time?
Hey Andy! - I didn't measure them exactly but the 18 stack was definitely quicker, however both were quite fast overall, my pc is pretty quick though - with a larger megapixel camera it would probably be a drag stacking hundreds!
I think I would go for the shorter subs bc you lose too much exposure time when its rejected by wbpp
I don't think you mentioned your Bortle zone. This is an interesting video as I have just bought a 10 Mircon mount and the consensus is guiding isn't needed for around five minutes or less depending on your model created for the mount and the focal length of your scope. If I can get away from the need to guide at say 1645 mm, I would be happy for shorter exposures. The test will be for F10 and 3 nm narrowband filters. Our skies here have been rubbish for nearly four years so I rarely take the opportunity to experiment with exposures. On a completely off topic note, I did narrowband exposures of a planetary nebula (PK 294-0.1 near the Running Chicken Nebula) at 645 mm (refractor @ F5.6) and at 2350 mm (reflector @ F10) and after cropping the refractor image, I couldn't see much difference between the two. It made me wonder why I bothered with the reflector considering how small the target was. Perhaps you might want to do something similar.
Thanks so much for sharing your results!! - I'm in bortle 7 skies here by the way, cheers!
I use 5 to 8 seond exposures in Sharp Cap unless I am using a dual band filter, when I go to 15 seonds. I never try using 1 to 5 minute exposures. I bore easily, while waiting for the next update.
but why...? What kind of hard drive space do you have to handle all of those frames?
Thanks Luke, taking into consideration how many subs I bin, it's shorter subs all the way from now on. This will no doubt result in more integration time per session. Again thank you for an unbiased test.
Glad to help my friend!
You are true and false at one moment. The main reason to use long subs is to catch dust + faintly visible details. For example you can`t use 60s subs on Iris nebula, just try. If your sky is not excellent and you are near the town - all details will be mixed with light noise. Also you can`t use short exposures with narrowband, the signal will not be enough.
P.S. I don`t know about you but I see difference in dust areas on your M51 (top-right corner). 300s catched more, and if you take more subs you better see this difference. Thx.
Heilung hey? 🤘
Remember that we all are brothers! :-D Such a great band!
Talk about getting down to the nitty gritty 😊
Thanks Keith!! :-D