Another Newbie M8

[mill (Martin)]

Just to show to Ken that you can get loads of detail from short exposures, here is as example M42.
20x10 Seconds unprocessed and 20x10 Seconds processed with curves and levels.
So if you can do 60 Second shots, do as many as possible and learn how to process those pictures

This is afcourse from my fairly dark sky back yard 32Km from Melbourne CBD.

[naskies (Dave)]

Originally Posted by bmitchell82

Well here is a comparison of a 5 second 90 second and a 600 second image taken on the same night same scope same camera. This i hope shows that data doesn't magically appear

I have done a basic curves and levels on these images to bring out a fair bit of the details that are present.

Hi Brendan,

I'm a newbie as well, so I'm very interested in what you're saying.

I'm curious whether you have come across the "skyfog statistics limited" approach to modelling the SnR (in terms of calculating exposure times)?

http://www.samirkharusi.net/sub-exposures.html
http://www.pbase.com/samirkharusi/image/37608572
http://www.starrywonders.com/snr.html

Basically, it says that the total integration time (i.e. number X duration of subs) correlates with SnR provided some assumptions are met - primarily, that the sky fog histogram peak for each sub is exposed just enough to separate from the left edge (but no more - to maximise dynamic range).

In that case, how would a stack of 120 x 5-second exposures compare to your 1 x 600-second image (equal integration time)?

Furthermore, if you took a 600-second exposure with an f/8 scope, wouldn't that give you a similar histogram to a 150-second exposure with a f/4 scope? Therefore, isn't the ideal/maximum subexposure duration affected more other factors - like sky fog - than just an arbitrary time limit? For example, a 10-minute sub at f/2 lens would probably be overexposed in most locations with even moderate light pollution.


Dave

[Poita (Peter)]

Originally Posted by mill

Just to show to Ken that you can get loads of detail from short exposures, here is as example M42.
20x10 Seconds unprocessed and 20x10 Seconds processed with curves and levels.
So if you can do 60 Second shots, do as many as possible and learn how to process those pictures

This is afcourse from my fairly dark sky back yard 32Km from Melbourne CBD.

That makes me feel so much better as the few single shots I have managed to take look a lot like the first image and I had been worried at the lack of detail
Time to get more data and get stacking...

[Poita (Peter)]

Originally Posted by bmitchell82

Well here is a comparison of a 5 second 90 second and a 600 second image taken on the same night same scope same camera. This i hope shows that data doesn't magically appear

I have done a basic curves and levels on these images to bring out a fair bit of the details that are present.

That last image has all the detail missing in the centre, is that a drawback to using longer exposures? Do you get around that by adding some short exposures in as well, or is it just a processing glitch?

[mill (Martin)]

Originally Posted by Poita

That last image has all the detail missing in the centre, is that a drawback to using longer exposures? Do you get around that by adding some short exposures in as well, or is it just a processing glitch?

Peter when doing High dynamic objects like M42 you blend in a shorter exposure into the longer exposure, see here http://www.iceinspace.com.au/forum/s...ad.php?t=81362

The long exposure on M42 will blow out the trap because it is very bright.

[jjjnettie (Jeanette)]

Short exposure AP is great fun. And you can achieve some pretty darn good images too.
You're learning the same processing skills as you would with long exposures.
Skills that will travel with you when you take the next step up the ladder.