Mixing sub lengths in the same stack

[ian_bird]

Hi

I was wondering if it is a good or bad idea to mix different sub lengths in the same stack.

For example I have 2 x 20 minutes and 6 x 30 minutes with an HaIi 3nm filter of Sadr. Should I put them all in one stack? I have some 300 second subs that I will use as a layer to control the bright region near Sadr and Sadr itself as per Olly's suggestion in another thread. But not sure if adding the 20 minute subs to the 30 minute ones will add to them, or subtract from them.

Any suggestions? Or  is it a "suck it and see" situation?

Also - is there any empirical way to measure the results of with and without? I'm using Maxim but also have PI and PS available. For example - can you measure the signal to noise ratio in the resulting image? How would you tell what was signal and what was noise?

Cheers

Ian

[wimvb]

As far as PI is concerned, have a look at this:

http://pixinsight.com/forum/index.php?topic=6767.0

Hope this helps

[ian_bird]

Thanks Wim.

Perhaps on balance I will leave the 2 x 20 mins out of it.

Cheers

Ian

[michael8554]

I suggest that you use as many lights as possible to tease out the fainter parts of the image, then control any over exposed areas with layer masks and your lesser exposure lights.

But what do I know.....

Michael

[ian_bird]

Thanks  Michael.

Cheers

ian