I currently use a 120mm achromat f5 as my guidescope and find no problems finding a guidestar with my QHY guider. Lots of you seem to use 80mm scopes instead.
I have tried guideing through my 200mm f8 main scope but with it's smaller field it can be harder to find a guidestar. When one is present however it is still just as easy to use.
In skywinty's
thread he is looking at an 80mm high f ratio scope as a guidescope.
So what is more important?
The larger the scope the more light collected and for point sources (guidestars
) the aperture shoud be more important than f ratio to find lower mag guide stars. A low f ratio will give a wider field and hence more area to find a star but shouldn't make any difference to the limiting mag.
Which comes out ahead? Field size or limiting mag?