Quote:
Originally Posted by torana68
thanks  without getting the calculator out whats that in terms of focal length with an 8"? |
You calculate the scope's field of view by dividing the eyepiece Apparent Field of View (AFOV) by the magnification the eyepiece has in the system of interest. So for an 8 inch telescope with say a 40mm (1.6 inch) eyepiece and a 50 degree AFOV, an F20 (efl=160 inces) scope would have a field of half a degree with a magnificaton of 100.
To put it another way:
eyepiece AFOV/Magnification = scope FOV
so in this example:
50 (AFOV)/100 (Mag)=0.5 (FOV)
Of course different eyepieces will yield different results but hopefully that explains how to do the calculation.
Hope that answers your question.
Rod