Potentially dumb question about spotting scopes

[phronq]

I'm thinking about a spotting scope, but I have absolutely no idea what to get based on the way they describe the magnification for these things.

I want to be able to see a 12" target 75 feet away and have it take up most of the field of view.

So what would that be in "A-BxC" terms? Someone clock me with the clue-bat.

I was looking at the lineup of stuff Efton Science has. They seem to have a rather extensive selection, and since it's going to be used indoors, I'm not worried about weather resistance.

 

[McVillan]

It's just like the description for a camera lense: A-B is the zoom factor.

A = lowest magnification
B = highest magnififation
C = aperature of the front element (the front piece of glass)

Generally (for a camera lense) the larger the front element the larger the largest f stop is. That is, the brighter the lense appears when looking through the viewfinder.

I think that most rimfires use something like a 3-9 power scope. That's for shots between something like 25-75 metres. For reference, I just bought a Bushnell 20-60 and at 100m a 10" target fills the lense and I can see the fire-extinguisher-sized gongs at 300m very easily.

Hope that helps.

 

[phronq]

Yeah, it does.. I have a better idea of what I need. Thanks!