Quote:
Originally Posted by Wavytone
Hi Ben,
The point of the larger 2" barrel eyepieces is that the true field of view is ultimately limited by the inside diameter of the eyepiece barrel. 2" covers 2.56X as much sky as 1.25" can.
Hold uo your eyepieces and look at the flied stop - the end that faces the telescope. The field stop is a black ring inside the barrel that defines the edge of field of view and quite simply it must be smaller than the inside diameter of the barrel.
Now... if you look at say a Vixen 42mm LVW, or a Televue 31mm Panoptic, or say an ES 40mm 68 degree eyepiece, they all have a field stop around 46mm which is about as wide as you will find in a 2" barrel. So these beasties will gove you a view of the widest patch of sky you can get in a 2" barrel.
But you can't get a 46mm field stop in a 1.25" barrel, its physically impossible.
There is also a trade-off between $$$ vs apparent field of view too, for example the ES 30mm 100 degree field of view will give the same ACTUAL field, with more magnification. The price is that it costs more, and distortion is also inevitable.
Now... with your f/10 scope, the longest useful focal length you could use is around 60mm (determined by the exit pupil) so you could easily opt for the lower cost eyepieces like the ES 68 degree series, there is really no point in spending megabucks for ultra wide Naglers, Ethos or similar.
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Just a clarification: the 30mm 100° ES eyepiece is a 3" eyepiece and has a field stop larger than 2", so if it were usable, it would produce a larger true field than any 2" eyepiece with a 46mm field stop.