T2 mount & aperture??

[Phil-D]

I have a T2 mount attached to a sleeve that fits snugly over a spotting scope eye piece, I use it on a Nikon D7200

Obviously I can only adjust SS and ISO, just out of curiosity, anyone know what determines aperture and what the reading will be?

 

[TimHughes]

As as I recall F number is the focal length of your spotting scope / diameter of the front lens. Eg 300mm / 30mm = f10? Worth a google.

 

[Phil-D]

As as I recall F number is the focal length of your spotting scope / diameter of the front lens. Eg 300mm / 30mm = f10? Worth a google.

Thanks Tim, now you've said, that makes sense and I feel I should have known!

The front element is 65mm with a 25x50 wide zoom eyepiece, higher the magnification equals less light, so smaller the aperture

I'll see if I can get some specs on the scope and work out an equivalent focal length, cheers

 

[TimHughes]

What’s the spec? 25x50 or 25-50x?

D7200 is a crop? So my guess is something like this - normal focal length for crop is say 35mm so 50x is 1750mm. Divide by 65mm gives f27.

Does that fit for what you see in practice with the camera?

 

[Phil-D]

What’s the spec? 25x50 or 25-50x?

Sorry, yes should have read 25-50x

You could well be right on the button here Tim

I was talking to a chap the other week who seemed to think that a scope with a fixed 20x eyepiece was equivalent to around 700mm (he didn't say how he knew ) but going off what you say it looks like he was right.

Mine at 25x multiplied by 35 will give a focal length 875mm, divided by 65mm gives an aperture of f13/f14 which sounds about right

Thanks for the help