I'm new but I don't see anyone else jumping in here so I'll give it my best. If
anyone can make my answers better or if anyone sees an error, please jump right
in.

Luminance: The goal is maximum exposure that doesn't completely saturate
highlights on the chip. I do a binned test exposure then use a pixel info
cursor on the test exposure. If I'm binning 2x2 on the test, I'll go for an
exposure of 75-90% the full capacity of the well, or in my case 50,000-60,000 on
the pixel value. When I do a nonbinned image, I'll multiply my test exposure
times 4. If there's no highlight saturation I'll usually go for 20 minute subs
although I have gone as long as 40 minute subs. I don't bin luminance and I'm
+/- on binning the color subs. I think most people do about 20 minute subs
generally. There's a trade off between higher S/N on the subs and other factors
such as aircraft, space junk, satellites, etc.

Ha is more difficult. I usually do 20-30 minute subs. You can use the same
technique, doing a binned image, testing the pixel levels, then multiplying
times the binned pixels. So if I find a 5 min exposure works binned 2x2, I'll
multiply the binned exposure times 4 for the unbinned exposure.

The number of subs hits diminishing returns at about 16. After that you don't
get much improvement even with enormous numbers of subs. Get good flats, that'll
do more for your images than about anything else. Good luck.

David


--- In Astroimaging_filters@yahoogroups.com, "kaykraftllc" <gthomas10@...>
wrote:
>
> Morning All!
>
> Likely another silly question from a new imager here. I have an SBIG
> STL-11000 camera with CLRGB & Ha filters from Custom Scientific. SBIG
> recommends exposure ratios of 2:1:1 on the RGB filters. Is there any
> general rule of thumb on the ratio for the L and Ha filters, or is as
> much L as possible the way to go?
>
> Thanks for helping in my learning curve!
>
> Gary Thomas
>