Quantity or quality ??

[Skipper Billy]

Tonight is the last chance I will get for imaging this season. :-(

I was really just setting up my EvoGuide (very nice it is too!)

As there were a few gaps in the clouds I pointed my scope at M3

So far I have gathered RG and B and have just started the Lum.

Looking at the subs in Blink in Pixinsight about half the subs are severely affected by cloud.

Am I better keeping the cloudy subs or deleting them and having less data but better quality ??

I have 20 x 120 seconds each of RGB binned 2x2 and will have 20 x 300 seconds of Lum binned 1x1

Thanks in advance.

[kens]

I'd delete them.

[Demonperformer]

You have two sets of subs: good data subs and bad data subs. Stack all your good quality subs and you should have a good quality result. Now add a load of 'bad' data ... the end result will be worse.

[vlaiv]

I would exclude cloudy subs from stack.

In theory, depending on type of cloud cover, smart stacking algorithm could deal with cloudy / bad data, but that would lead to uneven distribution of noise, making post processing much harder.

In reality, it is most likely that any software that you use right now won't be able to deal with it and you will end up with image that is full of strange gradients - like LP gradients but nowhere near that smooth / uniform. Post processing will be nightmare

 

[Skipper Billy]

Thanks very much all.

I might try both ways just to see how much difference it makes.

 

[wimvb]

3rd option. Use the subframeselector script in pixinsight and give each sub a weightfactor, depending on snrweight. Add this as a fits keyword. You can also add other factors to weigh in, such as fwhm and eccentricity. Then also set a rejection threshold. Finally save all subframes. PixInsight will sort all your subs, and the image integration tool will give better subs more weight in the stacking process. Optimise this process to increase the snr of the integrated image. For only 20 subs, this may seem overkill. But if the subs are 15 - 30 minutes each, we're talking about hours of integration time. And if you have 100+ shorter frames, you wouldn't want to do the sorting manually.

And of course, Kayron Mercieca has a tutorial on this: lightvortexastronomy.com

Good luck