Autoguider Guide Scope Focal Length

Hi all,

I am using an ST-4.

Is a Ranger (480 mm) long enough for a guidescope on an 1140 mm main scope (10 inch F 4.5 Meade Starfinder) riding on a G-11?

Alex

a good guideline for guidescopes is to have at least half the focal length of the main scope (I would prefer a lot more than half though). Are you guiding for film or ccd? with film, I would say throw a barlow between the ranger and st-4 and you'd probably be fine. CCD is usually a lot pickier.