Narrowband per channel total exposure time

[R26 oldtimer]

Hello all, I need your ideas on this!

With a mono camera and narrowband filters, should I be aiming for equal total exposure time per channel, or get longer total integration time for the fainter channels??

Also, is it a good idea to keep identical sub exposure time on all three channels, or should I try to have the histogram peek at the same point on all channels by adjusting my sub exposure time accordingly?

[vlaiv]

In principle - you should go for longer total exposure on fainter channels.

Problem with that is - you don't really know what is fainter channel until you start imaging. If you really want the best possible image, then here are a few pointers for that:

Ha is usually the strongest, followed by OIII and SII being often the faintest component. This is of course target dependent but for most of the targets it holds.

Don't be afraid to go out and capture additional detail. Most of the best images are captured over several nights. You can always start by allocating equal time slots for each channel and then once you do preliminary stack, check which channels lack in quality and go out the next night and get more data on those.

One more thing - if you use Ha as luminance, then it pays to have more time on it - Luminance needs to be smooth and we have much higher sensitivity for noise in luminance data than in color.

With individual exposures - in principle it is the same thing - you should "tune" exposure length for each channel. This will depend on two things - strength of signal and level and type of light pollution you have as well as width of you narrowband filters.

Again - you can't tell until you start shooting. Overall differences will be rather small and it really is not worth having different exposure lengths for each channel because you'll need different set of darks (if your camera can't use dark scaling, or even with dark scaling resulting SNR will be slightly different).

[knobby]

I'm very new to narrowband but echo what Vlaiv says, I'm still torn between trying longer subs on Oiii and Sii or just taking more of them to increase total integration time.

Edited November 15, 2020 by knobby

[tooth_dr]

I keep the same exposure for all NB filters, and start with a night of Ha, then at least if I dont get another night I have something to work with.  Oiii is next and then finally Sii if I can get the time or if I feel the image would benefit from it.  I find I often have more Ha.  Now with my dual mono rig I take Ha and Oiii one night and Ha and Sii the next night, thats been my pattern so far.