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I mainly use 5 and 10 minute exposures for LRGB and 20 and 30 minutes for narrowband with a FSQ-106ED (f/5) and a STL11K camera. I have a new camera with a deeper well depth (KAF16803 sensor) and I may play with some longer exposures. Even at 5 minutes I often need to add some shorter exposures with HDR to stop the stars from saturating and losing colour.
Cheers,
Rick.[/QUOTE]
Rick,
I think 5 minutes is too short for FSQ106 and STL11. 10 minutes would be minimum, 15 minutes better. SBIG or perhaps Wodaski has an exposure calculator that tells you the optimum exposure length for various cameras based on their characteristics. Of course that doesn't take into account tracking ability, clouds, wind, flex, narrowband or LRGB.
Marcus Davies noted an improvement in his SNR using an STL11 with 15 minute subs over 10 minutes. I used to use 15 minutes as my standard using STL11. Basically its a pretty noisy camera by todays standards (but still a lovely camera and so convenient) and you need to get the signal over the noise floor to register those really faint details.
If really faint details are not higher than the noise floor then I am not sure that many exposures will show that as they are not there to be noticed above the noise no matter what mathematics are employed.
To get above the noise floor for your camera (they vary) 15 minutes is probably the sweet spot for that camera in LRGB if your tracking and lack of cloud cover/wind allows it.
Greg.
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