[LewisM]

Is it wise to have the GS FL as near the main scope FL?

For instance, with my f/4 Pentax, would an f/3 guidescope (converted finder) be a good match? With my f/8 main, would an old f/9 converted Toya 50mm refractor be suitable?

I have use the f/9 GS on an f/6.3 main before with great results as well as the f/3 GS on the same scope. The f/4 Pentax surely should use the short FL GS?