[Shiraz (Ray)]

Hi Peter

I think that the big problem will be the noise component of the dark current, rather than the dark current itself - so signal to noise will be the main issue, rather than dynamic range. On that basis, you only need expose long enough to ensure that the (noise from the dark current + sky noise) will dominate the read noise and you will get as good as possible results with stacking. On that basis, with either camera, 2 minutes sounds about right (maybe a bit longer would be slightly better, but that is probably a reasonable maximum exposure anyway if you are taking along a portable tracking mount of some sort to do astrophotography). You could use longer exposures if the SX supports them, but you would not gain any extra image quality over that which you would get by stacking multiple short exposures (and stacked short exposures would give better dynamic range).

SX are very helpful and would probably clear up any questions re the maximum exposure possible with their software/hardware. the very nifty stacking software suggests that longer exposures are possible if you want to go that way.

Anyway, why not just use your existing Atik without cooling - the older chip doesn't quite match the quantum efficiency of the new one, but it is still pretty good (and it appears to have slightly lower read noise than the new one).