Mars 18 Sep 1h30 am-ish

On Sun, 18 Sep 2005 19:14:41 GMT, "Chris Taylor"
wrote:


"paul" wrote in message
.. .
On Sun, 18 Sep 2005 13:41:10 GMT, "Chris Taylor"
wrote:
Thanks for your reply Chris. Will a 3x Barlow improve my planetary
viewing? My 'scope is a Sky-Watcher Explorer 200, (D=200mm(approx. 8")
/ F=1000mm) on a HEQ5 mount.

Hi Paul

The rules change a little between imagers and the human eye on a scope. The
very general rule being 50x per inch of aperture for viewing with the eye.
ie about 400x for your scope |(absolute max) You'll lose some contrast going
this high and poor seeing conditions will make 400x unusable. So, 1000mm
focal length with a 2x barlow and a 5mm eyepiece will offer 400x. I'll go
out on a limb: You're probably better off around 200x. ie 10mm eyepiece and
2x barlow (which you're already using) or a 5mm eyepiece on its own.

Regards


Chris

Thanks for your advice.
paul