what length ? (1 Viewer)

Hi I am thinking about Digiscoping in the near future , presently using
Nikon D90 Or a Nikon V1 with a Sigma 500 or Nikon 300 prime lens
which gives me approx. 1350mm or 810 +1.7 tc
What would the same Cameras give me on a 85mm Scope ?
P.S I have a few images posted in the Gallery taken with these combos ,what I am finding to take Sea birds is very difficult even with the V1 +500 mm cheers Robert

Depends on the eyepiece used. The 35 mm equivalent focal length for digiscoping is: scope magnification*camera lens focal length*crop factor of the camera. Scope magnification is scope (objective) focal length/eyepiece focal length. You will also need an adapter for mounting your camera behind the telescope's eyepiece.