|
For the longer focal lengths, if you want a wider apparent field of view(AFOV) than the plossls which are around 50 deg, I'm fairly sure that the eyepiece has to have a 2" barrel. Eg, the 100 deg Ethos is a 2" in the 17mm focal length version. I have a 35mm Panoptic (68 deg AFOV) and a 30mm Chinese clone (80 deg AFOV) and both are 2".
Plus, it saves having to fiddle with the 2"--> 1.25" adapter when you have a 2" focusser.
|