What`s max fov in Mak 127 with 2 inch eyepiece?
Posted 18 January 2008 - 01:38 PM
Best regards Waldi
Posted 18 January 2008 - 02:07 PM
Posted 18 January 2008 - 02:57 PM
1) What is the focal length? There are F/10, F/11, F/15 even F/20 Maks.
2) Does the 127 mak accept a 2" Visual back or focuser?
The maximum focal length achievable with a given EP depends on the field stop of the EP, the capability of the telescope to fully illuminate that field stop, and the focal length of the telescope.
The maximum field stop for 2" EPs is about 46mm.
The maximum field stop for 1.25" EPs is about 27mm.
Assuming you have an F/15 Mak, your scope FL is 1905mm. In this case:
With 1.25" EPs: Max TFOV = 27*57.3/1905 = 0.81 deg.
With 2" EPs: Max TFOV = 46*57.3/1905 = 1.38 deg.
Typical 1.25" EP's yielding 27mm FS: 32mm Plossl, 24mm 68-degAFOV, 19-20mm Ultrawides (82-84 deg AFOV).
Typical 2" EP's yielding 46mm FS: 55mm Plossl, 41mm 68-deg AFOV.
Note again: If your MAK does not have enough of a rear opening to illuminate the field stop, you will get vignetting (darkening of the perimeter of the FOV). As this is a very real danger, I suggest you try before you invest (or wait for an answer from someone who actually has this specific scope).
Posted 18 January 2008 - 04:12 PM
Not exactly widefield viewing, but it frames the Perseus Double Cluster nicely.
Posted 18 January 2008 - 05:44 PM
Posted 18 January 2008 - 06:34 PM