|
A 2" diagonal will have a longer path length than a 1.25" diagonal thereby leaving you with less back focus.
A 2" eyepiece set is not necessary or typically available and most sets will have a combination of 2" and 1.25" or if they are only 2" they will be in longer focal lengths only. The barrel diameter simply limits the maximum true field possible. A short focal length eyepiece even with enormous apparent field will still only require a 1.25" barrel and most manufacturers will only make them as such. There are a few hybrid dual barrel eyepieces available in some focal lengths, eg. 12mm Type 4 Nagler.
Note not all diagonals have the same path length and sometimes you can gain valuable focus travel by choosing the right diagonal provided the information is available to make the choice and most suppliers won't publish this.
|