Eyepiece 'sizes'

With my Meade scope, I have a 26mm eyepiece. The size of the lens in
it is quite big, which makes it easy to point a camera down it and
take a photo (just for quick shots).

I've recently bought a cheap Celestron eyepiece (9mm) and the lens is
much smaller in diameter, and nearer the top - so your eye is almost
touching it. Because of how small the area you can see through is,
it's almost impossible to use a compact camera with that eyepiece. Is
this just due to the fact that it's a 9mm, and are most 9mm eyepieces
likely to be the same configuration? (This is a plossl, whereas the
26mm is a 'super plossl').

If I bought the Meade eyepiece of the same spec, would it be likely to
have a configuration closer to that of the Meade 25mm eyepiece ie.
larger lens and further away from your eye?

In article , Rexx Magnus wrote:
With my Meade scope, I have a 26mm eyepiece. The size of the lens in
it is quite big, which makes it easy to point a camera down it and
take a photo (just for quick shots).

I've recently bought a cheap Celestron eyepiece (9mm) and the lens is
much smaller in diameter, and nearer the top - so your eye is almost
touching it. Because of how small the area you can see through is,
it's almost impossible to use a compact camera with that eyepiece. Is
this just due to the fact that it's a 9mm, and are most 9mm eyepieces
likely to be the same configuration? (This is a plossl, whereas the
26mm is a 'super plossl').

If I bought the Meade eyepiece of the same spec, would it be likely to
have a configuration closer to that of the Meade 25mm eyepiece ie.
larger lens and further away from your eye?

My experience is the same as yours - the smaller the focal length of the
eyepiece, the smaller the lens is.

However, if you were to buy a 2x and/or 3x barlow you could use that with your
26mm eyepiece and have the equivalent of a 13mm e/p or a 9mm e/p (ok, 8.667mm)

My favourite planetary combo is a 5x Powermate and a 20mm e/p, as the 20mm e/p
has good eye relief and is just a nice e/p.

Jim
--
Find me at http://www.ursaMinorBeta.co.uk

Please help to bring two classic works of whisky literature back into print
by visiting http://www.ClassicExpressions.co.uk Thank you.

Rexx Magnus wrote:
With my Meade scope, I have a 26mm eyepiece. The size of the lens in
it is quite big, which makes it easy to point a camera down it and
take a photo (just for quick shots).

I've recently bought a cheap Celestron eyepiece (9mm) and the lens is
much smaller in diameter, and nearer the top - so your eye is almost
touching it. Because of how small the area you can see through is,
it's almost impossible to use a compact camera with that eyepiece. Is
this just due to the fact that it's a 9mm, and are most 9mm eyepieces
likely to be the same configuration? (This is a plossl, whereas the
26mm is a 'super plossl').

If I bought the Meade eyepiece of the same spec, would it be likely to
have a configuration closer to that of the Meade 25mm eyepiece ie.
larger lens and further away from your eye?

All Vixen LV eyepieces have 20mm of eye relief no matter what size you
choose and you'll find these second-hand for between £45 to £60 and are
a good investment for a decent eyepiece at that price.

John.

Jim wrote:

If I bought the Meade eyepiece of the same spec, would it be likely to
have a configuration closer to that of the Meade 25mm eyepiece ie.
larger lens and further away from your eye?

My experience is the same as yours - the smaller the focal length of the
eyepiece, the smaller the lens is.

That is the case. Of course there is some variation in different
qualities of lens. I have a couple that came with my cheapy Zennox
scope, and they are, well, unusable.

The eyepieces I got with my Helios Dob (identical to SkyWatcher) are
very good, and offer excellent eye relief on both the 10mm and 20mm.

I also got a set of budget eye pieces off eBay, and these are OK, but
when you compare them to the Helios ones, are obviously not as good.
There is a 4.5mm one, and I haven't even bothered with that.

However, if you were to buy a 2x and/or 3x barlow you could use that with your
26mm eyepiece and have the equivalent of a 13mm e/p or a 9mm e/p (ok, 8.667mm)

I agree, having now tried various combinations, a long eye relief eye
piece with a Barlow lens is usually better than a smaller (more
powerful) eyepiece. The views I get with my Antares 32mm are really
great.

My favourite planetary combo is a 5x Powermate and a 20mm e/p, as the 20mm e/p
has good eye relief and is just a nice e/p.

I need to get a more powerful Barlow I think, but I find myself looking
for Deep Sky Objects more now - mainly because the only planet I can see
is Saturn at the moment, and nice as it is, I've seen it lots of times
in the last few weeks. The 32mm and Barlow are a great combination for
DSOs though.

--
Andy Hewitt
http://web.mac.com/andrewhewitt1/

"Rexx Magnus" wrote in message
...
With my Meade scope, I have a 26mm eyepiece. The size of the lens in
it is quite big, which makes it easy to point a camera down it and
take a photo (just for quick shots).

I've recently bought a cheap Celestron eyepiece (9mm) and the lens is
much smaller in diameter, and nearer the top - so your eye is almost
touching it. Because of how small the area you can see through is,
it's almost impossible to use a compact camera with that eyepiece. Is
this just due to the fact that it's a 9mm, and are most 9mm eyepieces
likely to be the same configuration? (This is a plossl, whereas the
26mm is a 'super plossl').

If I bought the Meade eyepiece of the same spec, would it be likely to
have a configuration closer to that of the Meade 25mm eyepiece ie.
larger lens and further away from your eye?
The simplest solution, is to do what is done 'at heart' on more expensive
eyepiece designs, and add a Barlow. If you look at the internal designs of
more 'premium' eyepieces, generally, the shorter focal length units, will
include an element that is effectively functioning as a Barlow lens, to
get away from this exact problem. For a given AFOV, and a given lens
design, the diameter of the exit element will reduce as the focal length
goes down, and normally the eye-relief will reduce as well. The 'super
Plossl', might be fractionally better in this regard (but not a lot).
Unfortunately, the term covers a whole range of eyepieces with a
significant 'range' of designs, normally small modifications to the basic
'Plossl' design, so one needs to go for something beyond this to get a
real solution.

Best Wishes