Oculars plugin

[Diego Rodríguez Peregrin]

Stellarium asks Field Stop number to be filled in the New eyepiece form. But usually only focal lenght and apparent FOV are provided by manufacturers. As a matter of fact, FOV is usually calculated using the simplified expression Eyepiece Field of View / (Telescope Focal Length / Eyepiece Focal Length) that doesn't use Field Stop number at all. But still, Stellarium asks for it.

One way to supply it is just calculating the Field Stop d out of the usual formulae with fT and fE focal lenghts of telescope and eyepiece respectively:

FOV =2ATAN[d/(2fT)] so d=2fT TAN(FOV/2)
aFOV=2ATAN[d/(2fE)] so d=2fE TAN(aFOV/2)

Would it be nice if the plugin oculars could help calculate the missing Field Stop?

[Georg Zotti]

Please see what to do if you don't know this value in the description of the parameters in the User Guide, section 15.1.2.