{ Hi Deb! Long time listener, Long time facebook fan :P This was written for an astronomy group so some editing may be needed.}

I recently hosted a discussion about camera gain vs. exposure length trying to decide which way worked better while I was actually set up and shooting. One thing led to another and I ended up doing a conclusive study of gain vs. exposure times in which I was thoroughly convinced that lower gains worked better. The math on noise reduction via stacking doesn't add up with my particular camera, and indeed many cmos cameras should probably give this a try. The hardest part of course, and the case I originally made in that post, is that getting super long exposures is really tough and that you lose gobs of time when things go wrong, which they very often do. To get them, lots of stuff has to line up just right.
First you have to have a bunch of dark time handy, which can be tough if you work days. The next is good conditions. Some areas seem to get all the good conditions but I'm sure they have their pitfalls as well. These old mountains I live in toss everything at my rig at one point or another. Humidity, clouds, bigger clouds, wind, high wind, rain, hard rain, Virginia rain, freezing rain, hail, sleet, snow, doves, owls, gay frogs, small dogs... you name it. They all ultimately contribute to bad "seeing". The moon is another limiting factor for long exposure and for some strange reason those clear calm nights usually manage to line up with a big ole moon staring in the bedroom window.(cue howling coyotes)
Guiding is a must, and it needs to be settled well inside the 1arc second limit for round stars in order to have any hope of going the distance. I've found the biggest problem to be cable drag, but there are many factors that can ruin guided shots. One good gust of wind can mean the difference between excitedly watching the counter marching down to zero or disappointment when it decides to toss out 15 minutes of your life. Other factors include dec/ra balance, polar alignment, dirty or misaligned wormgears, noisy comm lines, or a pc that likes to lock up at the worst possible moment, usually right after you jokingly wrote something that might be misconstrued as a terrorist act, or the counter gets down to 28.4 seconds on a long exposure.

In conclusion, I was obviously wrong in my original argument and oh my what a difference that has made. I was already getting long guide runs so it was really just a matter of waiting till things all lined up.

I'm really proud of this one.

Cheers and Clear skies!

Pentax K5
Exposure: 1 x 900 seconds
guided by converted finderscope+asi120mc-s
ISO: 100
Telescope: TPO 6in F4 newtonian /GSO coma corrector
Skywatcher EQ6R-pro mount

One super long exposure, stored in 16bit fits format
Opensource Siril was used to debayer, color calibrate, stretch and remove green noise from the image.
Opensource Rawtherapee and GIMP were used to refine and resize the image for web use.