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2" eye pieces?


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i was just wondering wha the advantages of going with a 2 inch eye piece? i have a set of sirrius plossels coming for my recently delivered 8 inch dob. what does the 2 inch offer that the 1.25 inchers dont? what size would you say would work best on my telescope?

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Hi, a 2" eyepiece gives you a MUCH wider field of view & enables you to see a much bigger area of sky.

I have a 32mm Panaview for my 8" Dob & I love it.

What size/focal length you should get depends on your exit pupil amongst other things.

Have a look at the excellent thread below to help.


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  • 2 weeks later...

rpmiller78 - Astro-Tech are the equivilents to our skywatcher branded ep's, your side of the pond.


PanaView equivilents-



Aero equivilents-



Edited by AndyH
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Under about 17mm to 20mm there is no advantage in max FOV in using a 2" eyepiece over a 1.25". The max FOV is determined by the size of the field stop in the eyepiece barrel and it's not until you get to the longer focal lengths that you would need a larger field stop than is possible to fit in a 1.25" barrel.


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Try not to think about 2" as a feature that makes an eyepiece better - it doesn't by itself. A 2" barrel diameter is necessary when a wide field at certain lower powers is needed. If you put in a 12.5mm BGO on a 2" barrel (and made it work) it wouldn't get any better, optically. A 31mm Nagler or a 21mm Ethos wouldn't be able to achieve their wide fields without a 2" barrel, however. The only other real advantage is that with heavier eyepieces, the 2" barrel feels much more secure in a focuser than a 1.25" one. But it's not a case of "more inches = better"; you can use a 10mm Ethos in both 1.25" and 2" modes with no optical difference whatsoever.

Edited by newman
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