Re: plossles and eye relief
- From: "dkelvey@xxxxxxxxxxx" <dkelvey@xxxxxxxxxxx>
- Date: Thu, 28 Feb 2008 10:25:39 -0800 (PST)
On Feb 27, 7:56 pm, Shawn <scurrynospamme...@xxxxxxxxxxxxxx> wrote:
Cole Sachs wrote:
What is considered good eye relief for a 7 or 8 mm plossle design so that
people with eyeglasses don't have a problem and you don't have to
put your eye practically on the EP?
Any 8 mm plossl will give you 5mm or so of eye relief. Look into
Televue Radians or William Optics SPL eyepieces. Both are more complex
than plossl designs (6 or 7 elements vs. 4 for plossls), and provide
20mm of eye relief. My minimal understanding of eyepieces is that any
plossl design eyepiece will give about the same field of view, eye
relief, and aberration, as any other of the same focal length.
Shawn
Hi
The only way to get a long eye relief that I've seen is to take 25mm
plossl
with good eye relief and place a small negative lens to extend the
effective
focal length of the telescope, as is done in Orions Lanthinum
eyepiece.
Essentially using a Barlow.
Maybe one should just use a Barlow and live with that. A 3X Barlow
on a 25mm would be about a 8mm with long eye relief.
Dwight
.
- References:
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- From: Cole Sachs
- Re: plossles and eye relief
- From: Shawn
- plossles and eye relief
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