RASC Hamilton Pentax Astro Tracer

[Colin Haig]

At 07:51 AM 30/11/2013, Andy Blanchard wrote:
>Hi Mark, I was wondering why you think the best way to do dark 
>subtraction is to let the camera do it? Is this based on fact or 
>conjecture? As I have been telling my students just the opposite.

I've done a whole bunch of testing, and am finding that for exposures 
of perhaps a few seconds to a couple minutes (which is the limit 
arond here), getting the camera to do the dark works fine. Longer 
exposures, I'm undecided. If your plan is to grab a bunch and stack, 
then think turning it off makes sense and shoot a handful of darks vs 
doubling your exposure time, and reducing your productive shooting hours.
On the other hand, Alan Dyer was fairly insistent on letting the 
camera do the work in all cases.
Cheers
Colin