What criteria do you use in selecting a spotting scope?
I'm thinking about getting another scope to go with my ED50. What do you look for in a scope? Maybe this thread will help others who are shopping for a new scope as well.
I generally evaluate a spotter in this way:
1. A 2mm exit pupil is as small as I want to go with a spotting scope. Many consider 5mm the minimum for binos, but in good light I have found that 2mm is good with spotters. At dawn and dusk, a bigger exit pupil will be needed.
2. With a 2mm exit, the max useful magnification of a 50mm scope is 25x (60mm is 30x, 80mm is 40x, 100mm is 50x).
3. I want 1x magnification for every 100 yards, minimum to spot a buck. More magnification is needed for good evaluation. In other words, you "should" be able to spot and roughly evaluate a buck at 100 yards with your naked eye if he's mostly in the open. In heavy cover you'll need more magnification. At 500 yards, I want 5x... at 1000 yards I want 10x minimum... and so on.
4. So a 50mm scope is good to a "max" of 2500 yards for me (3000 yards for 60mm, 4000 yards for 80mm, and 5000 yards for 100mm).
This is a just a rule of thumb that I keep in my head when thinking about scopes. It seems to match my observations in the field, and when testing scopes in general. Of course, optical quality, atmospheric conditions, etc. will also have an effect.
Anyone care to share their thoughts and ideas on what applications are best for different size scopes? If weight wasn't an issue I bet we'd all carry 100mm spotters!