What f number do I have (1 Viewer)

Just bought an Opticron HR80 GA ED scope and 41110 Telephotoadpter to attach to my Canon 50D.
Can someone tell me how to work out what f number I am getting and what focal length. Also I would be very grateful for any tips on camera settings and what head to use as my Manfrotto ball head is not steady enough.
Sorry for the questions but this digiscoping is a whole new ball game to me.
Thanks.
Dai

Well according to this page it will be 1350mm / f.16.8 on the HR80. Multiply by 1.6 for the effective focal length/f ratio for Canon dslrs. Images through the veiwfinder will be very dim. Also will need to shoot at ISO400 minimum to get decent shutter speeds. This is way above the diffraction limit for the 50D too so with all this working against you, I would not expect much in terms of pic quality.

good luck,
rick