Quote:
Originally Posted by Zubenel
Hi , May I ask a question?? With the rise of big Dobs and increase in diameter of primary mirrors has there been an increase in eye piece diameters?? As far as I can see ( pun intended)  the answer is no. In last months Sky and Tel a 55mm eye piece was used in the 100'' Hooker Telescope on Mt Wilson giving 5.5arc minutes!! I know that apparent FOV's have increased dramatically in recent years but would a 100mm eyepiece need a 4" focuser as I love a wide FOV? |
I am not an optics expert so my comments may not be appropriate but I like to enter these kinds of discussions and see what comes of it.
The benefit of a larger barrel on the eyepiece is to enable a wider field of view at shorter focal lengths. This has little to do with the aperture of the scope as far as I know.
Most scopes today accept 1.25" eyepieces and there are variants that go to 82 degree AFOV and wider, but they are typically at the shorter focal length/higher mag end of the spectrum.
2" eyepieces allow wider FOV at longer focal lengths and are generally used for low power wide field use. Some have 100 or higher AFOV.
I don't think the use of bigger mirrors in hobby astronomy world really necessitates more than a 2" eyepiece unless you were going to very very long focal lengths.
As noted above there are larger eyepieces that are used at observatories but even a 25" mirror F5 scope would likely not need larger than a 2" focuser.
The 25" Obsessions, for example, use 2" focusers
http://www.obsessiontelescopes.com/a...sers/index.php