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11 mm and 50mm Eyepieces

Started by blueflagella, 03/14/2004 05:02PM
Posted 03/14/2004 05:02PM Opening Post
I have an 8" f/6 1200mm focal length DOB. I have gottn hooked on 2" eyepieces, especially for viewing DSO's.
I am in the market for a 11mm eyepiece and a 50mm eyepiece with excellent FOV. With so many eyepiece selections out there my brain is about to explode(Did anyone see that movie Scanners?)Pound for pound I am looking for the best eyepieces out there, but there's a catch, I don't have the cash to go after the nice expensive eyepieces.
Can anyone help on deciding which eyepiece, and why, is best for my scope?
Thanks
On a budget
Todd
Posted 03/14/2004 11:50PM #1
Number one piece of advice is to not get a 50mm ep! You won't get any more true field of view than, say, the 40mm MK-70 from University Optics, and you'll be losing a lot of light. The exit pupil produced by the 50mm with your f6 scope will be over 8mm in diameter - which is much bigger than your pupil, which means you'll be wasting light. At some point, with Newtonian scopes, with large exit pupils you also start seeing a "shadow" of your secondary mirror. Bad.

Stick to no more than a 40-42mm eyepiece. You don't have that many options above that range anyway!
Posted 03/16/2004 07:21PM #2
Todd

50 mm then consider a 2" Meade or Tele vue plossl.

11 mm if you are on a budget consider a 10.5 mm Meade plossl or a 11 mm Tele vue plossl. 50 degree filed is wide and nicely defined. Eye relief is O.K. Contrast very good.
Plossl's work well at f 6.
Or perhaps a UO orthoscopic, 45 degree field and sharp optics.
A 10 mm TV radian is another choice but expensive.

Any 11 mm eyepiece at 2" with a 65 degree field worth its salt will be expensive. I reckon the Tele vue will out perform most fo them in terms of contrast.

Best wishes
Kevin