How to take globular clusters

[Atacamallama]

I have an F7 102 mm apo and colour CCD. What length sub frames should I use to take a globular cluster? I'll confess that I have been a bit snooty about doing star clusters... and have never done them very much, as often as not rather disdainfully on moon nights.... I hear different ideas about how long subs should be, so as not saturate, etc. etc.

Any input welcome.

TIA

[rfdesigner]

With globs you will want your stars to be as tight as possible.. longer subs are likely to make stars bloat and can cause star stauration so for that aim towards shorter subs.

So as not to saturate your image. take say a 1minute frame, then check how bright the core of the glob is on your setup. if it's more than about 40,000 ADUs on any pixel then go shorter, if the highest is less than 20,000 ADUs you can afford to lengthen the shot.

Derek

[Atacamallama]

ok, I think I'm getting the pic, how do measure the ADUs? Do I use Maxim for that?

[rfdesigner]

I have an Atik CCD camera and use the Artemitis program to drive the camera and filter wheel, then I process in IRIS. In both cases it's possible to place your curser over a bright spot and read the intensity in the bottom right hand corner.

I don't know about Maxim, but I would be astonished if it didn't have that or something much much better

Derek