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#1 rbc1us

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Posted 15 June 2019 - 03:24 PM

can any one tell me whats the point of takeing 100 or 200 or 300 60 sec shots on a single shot color cam I don't under stand what you gain any help would be appreciated im new to single shot cam



#2 bobzeq25

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Posted 15 June 2019 - 03:31 PM

can any one tell me whats the point of takeing 100 or 200 or 300 60 sec shots on a single shot color cam I don't under stand what you gain any help would be appreciated im new to single shot cam

More total imaging time always gets you better signal to noise ratio. 

 

The optimal subexposure time depends on the read noise of your camera and your light pollution level.  Once you're in the ballpark there, more subs are always better.

 

Explained in more detail, with graphs, here (and other places).

 

https://jonrista.com...duction-part-1/

 

A decent way to think about it is this.  More total imaging time means you gather more signal.   Twice as much total imaging time, 2X as much signal.  But noise goes up as the square root of the total imaging time.  Twice as much total imaging time only increases the noise by 1.4X.  So, it's a winner.


Edited by bobzeq25, 15 June 2019 - 03:35 PM.

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#3 OldManSky

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Posted 15 June 2019 - 03:42 PM

To add to what Bob said...

 

You could do a single 20-minute shot instead of 20 1-minute shots -- and you'd only get read noise from 1 shot.  You win, right?

Except you don't win.

The 1600 (and every other camera) has a limited "well depth" -- how many electrons can fill a pixel before it saturates.  Once a pixel saturates, it's pure white and you lose any color information.  On a 20-minute shot, all your stars will saturate their pixels, and you won't see any color in any stars except for the very dimmest ones.  You'll also probably blow-out (saturate) parts of nebulae and galaxy cores.

 

If you, instead, shoot 20 1-minute shots, you get the noise benefits Bob described, without blowing out stars and galaxy cores and nebulae.  Now it really is win-win.

 

Not to mention satellite trails, kicking the mount, etc. -- which if they happen at the end of a 20-minute exposure, you've just wasted 20 minutes.  If they happen at the end of a 1-minute exposure, you only lose 1 minute.  Win again.

 

So, yeah -- shoot short and stack.  Make your exposures long enough to swamp the read noise, and not saturate stars.  You win.


Edited by OldManSky, 15 June 2019 - 04:19 PM.

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#4 rbc1us

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Posted 15 June 2019 - 03:51 PM

thank you for the response so then I stack all those images together and make one image? using another program like regi stacks

 



#5 2ghouls

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Posted 15 June 2019 - 04:06 PM

thank you for the response so then I stack all those images together and make one image? using another program like regi stacks

Yes, except registax is for lunar/planetary. Use DeepSkyStacker (free) instead for deep sky astrophotography.

#6 bobzeq25

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Posted 15 June 2019 - 05:06 PM

Imaging DSOs (with 60 second exposures, I'm guessing that's what you are doing, and this forum is for DSO imaging) is very complicated.  This book will get you started.  While it says "DSLR", much of the information applies to your camera.

 

http://www.astropix....bgda/index.html

 

If I'm wrong, and you want to image planets, this book.  Again, it's not just for DSLRs.

 

http://www.astropix....gdpi/index.html



#7 17.5Dob

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Posted 15 June 2019 - 10:40 PM

can any one tell me whats the point of takeing 100 or 200 or 300 60 sec shots on a single shot color cam I don't under stand what you gain any help would be appreciated im new to single shot cam

I'm not sure I understand your question.

Are you trying to stack planetary/lunar images, in which case you need to shoot video and stack several 10's of 1,000's of video frames...

Or are you trying to shoot DSO's ?

In that case you want to capture as many single exposures as you can, without destroying your star colors, and then stack them together, to reduce your shot noise.

After shooting 300, 45" subs, this is what I got by stacking....3 1/2 hour of shooting for this.......

48070604212_18aeb9a7fa_o.jpg

 

 

Even after stacking, you still only have the same exposure depth as your original shot......but now you've reduced the noise levels down to a point that you can do this in post processing, the most critical part of AP.

This is the above stack after post processing

40465965153_e88a979f12_o.jpg


 


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