Had a nice customer this morning call and ask to return a 100mm spotting scope he had recently purchased. When I asked why, he said it was no brighter or sharper than his old 70mm Bausch&Lomb. Of course, no problem, we agreed to take it back and help him choose a different product.
When he asked why the 100mm didn't out perform his old 70mm, it reminded me of a saying uttered by more than one astronomer to the effect that the eyepiece is half the telescope. In the case of many of today's cheap to mid-level spotting scopes, especially ones equipped with zoom eyepieces, this applies in spades.
If the customer's 100mm scope had other eyepieces available, it might have done a little better. Problem is, though, that most scopes at this level don't have other eyepieces available - you're stuck with whatever is attached to the back end of the scope.
Even on high end scopes, I have found that different eyepieces can have a huge effect on performance. Just because an eyepiece cost a lot, is no guarantee it will perform on a level with its price tag. Only way to ever know is to look and look with a critical eye.
It's a tough job looking through all our spotting scopes, but someone has to do it. Oh well.
