|
Rough rule of thumb is the eyepiece barrel diameter needs to somewhat larger bigger than the eyepiece focal length otherwise the apparent angular field of view is going to be quite limited. In typical modern eyepeiece designs this would give a modest 40-50 degree field of view which isn't anything soecial.
You could build a 100mm eyepiece with a 1.25" barrel but it would be light looking through a toilet roll - with a field of view may be 10-15 degrees.
Big telescopes have big focal lengths. Even with big eyepieces these scope are high-power only. For example a 1 metre f/15 cassegrain has a 15,000 mm focal length; putting a 100mm eyepiece behind that gives 150X.
|