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Daytime infrared speculation

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#1 GSBass

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Posted 04 December 2020 - 08:42 AM

I am not experienced enough to know for sure what’s going on but wanted to share my thoughts on daytime infrared since I’ve tried it several times since taking the image below shortly after getting the 462c, the main thing I noticed is after setting up in daytime and taking a few shots, after nightfall there is a pretty huge difference in exposure/gain on the exact same area of the moon, speculate your compensating for ir glow... but it does not seem to affect resolution. I bring this up because in post processing daytime infrared is actually easier to bring out shadows without blowing highlights, not enough people doing these to really get a firm grip but it is interesting and different. I guess overtime if I do more setups just before dark and do side by side comparisons I can pinpoint advantages or disadvantages

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#2 spereira

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Posted 04 December 2020 - 09:03 AM

Moving to Lunar Observing & Imaging.

 

smp


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#3 Borodog

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Posted 04 December 2020 - 10:03 AM

That is a beautifully sharp shot.



#4 GSBass

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Posted 04 December 2020 - 02:50 PM

Thanks, I expected night shots to be better but so far I like my daytime shots better

That is a beautifully sharp shot.



#5 Tom Glenn

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Posted 04 December 2020 - 04:04 PM

The daytime sky hides the deepest lunar shadows, which compresses the effective dynamic range of the Moon into a smaller region.  This can give the impression that processing is easier, but this is only because substantial portions of the data is completely obliterated from the recording.  If you want the deepest shadow detail near the terminator, you will have to image once the skies are darker.  That said, the sky doesn't need to be very dark, and light pollution is certainly no problem.  



#6 GSBass

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Posted 04 December 2020 - 09:27 PM

What you said makes sense but if you compare the above image directly with night shots the 462 seems to succeed where other cams don’t..... I consider the 462 a pretty revolutionary camera in this aspect, what you are saying was certainly true before the 462 came out

The daytime sky hides the deepest lunar shadows, which compresses the effective dynamic range of the Moon into a smaller region.  This can give the impression that processing is easier, but this is only because substantial portions of the data is completely obliterated from the recording.  If you want the deepest shadow detail near the terminator, you will have to image once the skies are darker.  That said, the sky doesn't need to be very dark, and light pollution is certainly no problem.  



#7 GSBass

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Posted 04 December 2020 - 09:38 PM

Just to expand on processing... the main difference in the steps is setting the black level before preceding with normal processing, just picking a shadow or space that your confident should be pitch black, once that is done it will allow easier processing of gray scales without blowing out highlights... at least to a lesser degree than nightshots



#8 GSBass

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Posted 04 December 2020 - 09:56 PM

Btw, not award winning but I am able to pick up some detail on Jupiter during the day also

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#9 Tom Glenn

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Posted 04 December 2020 - 10:30 PM

What you said makes sense but if you compare the above image directly with night shots the 462 seems to succeed where other cams don’t..... I consider the 462 a pretty revolutionary camera in this aspect, what you are saying was certainly true before the 462 came out

I'm somewhat confused by what you are saying.  If you are saying the 462 is better at daytime imaging than other cameras, then I am not disputing that.  But it appeared as though you were saying that imaging results are better during the daytime than in dark skies.  Maybe I misinterpreted you, but if that is what you meant, then it is incorrect.  The daytime sky masks out the shadow detail.  The images you are showing are fine, but they are not somehow proving that imaging during the day is superior to imaging at night.  



#10 Tom Glenn

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Posted 04 December 2020 - 10:46 PM

Your comments make me wonder, however, what your normal processing scheme is?  You mention the black level, but what sort of gamma correction are you using?  The images that come from your camera are linear, and need to be gamma transformed for them to look normal.  Shots taken at night, with high amounts of contrast, will look very abnormal, and indeed the shadows will be difficult to bring out without blowing the highlights, unless you are gamma correcting the data.  Look at the examples provided in the post below of the raw file compared to the gamma corrected image.  "Normal" cameras that we use everyday do this for you, but for astronomy cameras you have to do it yourself.  Most people skip this step for planetary images, because the result look better without gamma correction, but for the Moon it is hopeless.  

 

https://www.cloudyni...ons/?p=10081738



#11 GSBass

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Posted 05 December 2020 - 08:11 AM

Yes I am saying I believe you can get better results on the moon with the 462 in daylight , no gamma correction and of course I am comparing it to the same infrared shots taken at night, not color shots because that would be an apples and oranges comparison, I also have to stipulate that it’s only a couple hours before sunset, there is less ir interference it seems if I can set up in the shade of the house...makes it easier to see what I’m doing anyway without having direct sunlight. Processing is fairly normal, I use astrosurface and adjust white and black point before applying any wavlets or filters. As I said before, the reason I think you get better results is the ratio between the darkest darks and brightest whites is less during daylight, detail is still there, it’s just easier to bring them out with out destroying the other end, I typically aim for 5.4 ms and adjust gain accordingly and I under expose slightly 

Your comments make me wonder, however, what your normal processing scheme is?  You mention the black level, but what sort of gamma correction are you using?  The images that come from your camera are linear, and need to be gamma transformed for them to look normal.  Shots taken at night, with high amounts of contrast, will look very abnormal, and indeed the shadows will be difficult to bring out without blowing the highlights, unless you are gamma correcting the data.  Look at the examples provided in the post below of the raw file compared to the gamma corrected image.  "Normal" cameras that we use everyday do this for you, but for astronomy cameras you have to do it yourself.  Most people skip this step for planetary images, because the result look better without gamma correction, but for the Moon it is hopeless.  

 

https://www.cloudyni...ons/?p=10081738



#12 Tom Glenn

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Posted 05 December 2020 - 12:13 PM

As I said before, the reason I think you get better results is the ratio between the darkest darks and brightest whites is less during daylight, detail is still there, it’s just easier to bring them out with out destroying the other end,

The ratio is less, but this is why the amount of information recorded is also less.  The daylight sky is added to the light from the Moon (or any object).  This masks the faintest signals.  If what you were saying was true, that imaging was better during the day than at night (at any wavelength) then it would upend everything we know about astronomy, and research agencies could save money by not worrying about locating their observatories at dark sky locations.  When you image the Moon at night, the highlight regions remain just as bright as they were before (no brighter), but now you subtract the sky brightness, and so the darkest regions become detectable in the image.  This is most readily observed if you try and record the Earthshine portion of the Moon.  But obviously the Moon is so bright that you can get decent results during the daytime.  But not better than at night. What you are describing is an issue with processing.  The large contrast between highlights and shadows can be difficult to deal with, and it is hopeless if you are not doing a curves transformation to the raw linear image.  The white point should never have to be adjusted if the image was exposed properly, and no levels adjustments (white, black, or gamma) should be performed before applying any wavelets or sharpening filters.  That would be a guaranteed way to blow out the highlights.  In fact, the final tonal adjustments are the very last thing that should be done in processing.  These adjustments may appear easier on a "daytime" shot, because of the muted contrast, but this isn't making the final image better.  That said, your image posted is quite nice!  



#13 GSBass

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Posted 05 December 2020 - 01:15 PM

I can only say technology marches on, I’m convinced just through experience using the camera, I have read a good many articles on infrared supporting what you are saying however as chips become more sensitive with lower noise those conclusions may need to be retested, it’s not a ton of background that needs to be subtracted out because the exposures are so short, honestly do not think I am losing any detail....I’m certainly very close to the resolution of the scope just from analyzing what I am seeing. On the last thing you mentioned... this may have more to do with astrosurface but I do get better results by adjust basic light levels after stacking but before wavlets.... tried it both ways on planets and the moon... you can get similar results both ways but adjusting those before wavlets gives you a more stable image to post process, I think it helps mostly to keep noise under control

The ratio is less, but this is why the amount of information recorded is also less.  The daylight sky is added to the light from the Moon (or any object).  This masks the faintest signals.  If what you were saying was true, that imaging was better during the day than at night (at any wavelength) then it would upend everything we know about astronomy, and research agencies could save money by not worrying about locating their observatories at dark sky locations.  When you image the Moon at night, the highlight regions remain just as bright as they were before (no brighter), but now you subtract the sky brightness, and so the darkest regions become detectable in the image.  This is most readily observed if you try and record the Earthshine portion of the Moon.  But obviously the Moon is so bright that you can get decent results during the daytime.  But not better than at night. What you are describing is an issue with processing.  The large contrast between highlights and shadows can be difficult to deal with, and it is hopeless if you are not doing a curves transformation to the raw linear image.  The white point should never have to be adjusted if the image was exposed properly, and no levels adjustments (white, black, or gamma) should be performed before applying any wavelets or sharpening filters.  That would be a guaranteed way to blow out the highlights.  In fact, the final tonal adjustments are the very last thing that should be done in processing.  These adjustments may appear easier on a "daytime" shot, because of the muted contrast, but this isn't making the final image better.  That said, your image posted is quite nice!  



#14 Tom Glenn

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Posted 05 December 2020 - 01:31 PM

Well, we're departing from any assessment of your image (which is good), and now engaging in a debate on imaging in general.  What you are saying just doesn't make sense.  Whatever advancements exist in sensors, and no matter how good the daytime performance is, if you image the same scene after sunset when skies are darker you would collect even more information (all else being equal).  This doesn't mean the final image would necessarily be better.  The following image I posted below was taken after sunrise (by only 30 minutes, but doesn't suffer for it).

 

https://www.cloudyni...tor-aug-3-2018/

 

But what you are saying about somehow the background sky brightness improving the image doesn't add up.  There's a reason why on the planetary forum you don't see people doing much daytime imaging (except for Mercury and Venus), and there is currently much discussion about how best to image the Saturn and Jupiter conjunction given that the sky will be bright.  There are some ways to mitigate this, but it is never ideal.  



#15 GSBass

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Posted 05 December 2020 - 01:54 PM

That’s a beautiful image, better than anything I have taken so far.... I wish I had a preprocessed image to send you right now, I think you are thinking I’m turning a grey background black, the space surrounding the moon an hour or two before sunset is black, you can just make it a shade blacker, post processing I can look closely at my shadows and reclaim them if I went too far..... but anyway I think I led you astray with the amount of infrared scatter this camera records.... it’s very little.... now that was different when I imaged Mercury mid venus mid day, I picked up a lot of scatter on those shots and no doubt I lost detail on those. I can also say imaging Jupiter a hour before sunset does not change detail by much... it would probably be an excellent camera to image the upcoming conjunction however my fov is too small through my mak..... and that I guess is the one more thing... my mak may very well be the reason I have such good luck with daytime infrared, high Rez and high contrast are a default of that scope

Well, we're departing from any assessment of your image (which is good), and now engaging in a debate on imaging in general.  What you are saying just doesn't make sense.  Whatever advancements exist in sensors, and no matter how good the daytime performance is, if you image the same scene after sunset when skies are darker you would collect even more information (all else being equal).  This doesn't mean the final image would necessarily be better.  The following image I posted below was taken after sunrise (by only 30 minutes, but doesn't suffer for it).

 

https://www.cloudyni...tor-aug-3-2018/

 

But what you are saying about somehow the background sky brightness improving the image doesn't add up.  There's a reason why on the planetary forum you don't see people doing much daytime imaging (except for Mercury and Venus), and there is currently much discussion about how best to image the Saturn and Jupiter conjunction given that the sky will be bright.  There are some ways to mitigate this, but it is never ideal.  



#16 Tom Glenn

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Posted 05 December 2020 - 02:20 PM

I would agree that excellent results can be obtained with the Sun above the horizon.  This will be dependent upon the target brightness, as well as the angular separation from the Sun.  A crescent Moon is more difficult to image during the day, whereas a Moon that is 90 degrees away or more from the Sun can look quite good slightly before sunset or slightly after sunrise.  The only thing I was objecting to is your claim that increased sky brightness somehow improves an image. Increasing sky brightness (and the reduction in contrast that occurs) never improves astro images, but is an obstacle to be dealt with.  I would say that the use of IR filters can allow you to succeed in spite of sky brightness, not because of it.



#17 GSBass

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Posted 05 December 2020 - 02:33 PM

I only had one attempt at a daytime crescent, here are a couple shots from that

I would agree that excellent results can be obtained with the Sun above the horizon.  This will be dependent upon the target brightness, as well as the angular separation from the Sun.  A crescent Moon is more difficult to image during the day, whereas a Moon that is 90 degrees away or more from the Sun can look quite good slightly before sunset or slightly after sunrise.  The only thing I was objecting to is your claim that increased sky brightness somehow improves an image. Increasing sky brightness (and the reduction in contrast that occurs) never improves astro images, but is an obstacle to be dealt with.  I would say that the use of IR filters can allow you to succeed in spite of sky brightness, not because of it.

 

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#18 GSBass

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Posted 05 December 2020 - 02:34 PM

2

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#19 GSBass

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Posted 05 December 2020 - 02:37 PM

Not saying those are good, just sharing since you mentioned crescent.... actually considering buying a 485c because my fov is so small... however it’s not a infrared achiever like the 462




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