ASTRO: eyepiece help (orthoscopic)

I have an old 9mm celestron ortho that I just took apart. All the
diagrams I've seen of eyepieces show this lens configuration as Plossl.
Are celeston orthos really plossls? It's a pair of cemented doublets.
Also, if you happen to know the order they go in, drop me a line. I have
one cemented pair slightly larger than the other, a spacer and two
baffles (one wide and one narrow).

Thanks!
--
Adriano

Adriano wrote:
I have an old 9mm celestron ortho that I just took apart. All the
diagrams I've seen of eyepieces show this lens configuration as Plossl.
Are celeston orthos really plossls? It's a pair of cemented doublets.
Also, if you happen to know the order they go in, drop me a line. I have
one cemented pair slightly larger than the other, a spacer and two
baffles (one wide and one narrow).

Thanks!

Orthos I have all are a three element field lens and single eye lens.
Determining which is end of the triplet goes toward the mirror is
difficult. In theory it is the fatter of the two double convex lenses.
First time I take mine apart I put an arrow on the side pointing to
the objective. If that wears off I'm in trouble. The less convex side
of the eye lens goes toward the eye. Symmetrical or plossl are
doublets. Symmetrical are, well symmetrical so both lens pairs are the
same, convex to convex. In a plossl the field lens is often larger than
the eye lens. Also the objective side of the field lens is flat to
concave and often thicker (not by much) than the eye lens. The flat
side of the eye lens goes toward the eye. The convex lenses of each
pair face each other.

But there's so many variations out there, sounds like you have one of
those. I can't say what the Celestron version is like. We got one with
the C14 at Hyde in the mid 70's. It was awful and is never used. It was
the only ortho I ever saw that was lousy. Even some cheap ones I saw
were excellent. I've seen far better Kelners than that Celestron Ortho
we got. I never took it apart to see what was inside.

Since you are still using yours it obviously is a much improved version
than ours so likely wouldn't help to open it up. The doublet
arrangement sounds like a plossl design to me.

See this URL for diagrams.
http://www.hypermaths.org/quadibloc/science/opt04.htm

As a side note, my ortho's work best for eyepiece projection if they are
used upside down. That is, with the objective side toward the film or
CCD. I get far less curvature and edge distortion that way. But then I
never took a Jupiter as clear as the one you just posted so you're way
ahead of me!

Rick
--
Correct domain name is arvig and it is net not com. Prefix is correct.
Third character is a zero rather than a capital "Oh".

On Sat, 09 Jun 2007 14:04:53 -0800, Adriano
wrote:

I have an old 9mm celestron ortho that I just took apart. All the
diagrams I've seen of eyepieces show this lens configuration as Plossl.
Are celeston orthos really plossls? It's a pair of cemented doublets.
Also, if you happen to know the order they go in, drop me a line. I have
one cemented pair slightly larger than the other, a spacer and two
baffles (one wide and one narrow).

Usually the field lens is larger than the eye lens. The recess in the
eye cap of the eyepiece should give you a clue as to which lens goes
there. The crown faces of the lenses probably face each other. A
little trial and error might be called for.

Bud
--
The night is just the shadow of the Earth.

Thanks for the help Rick. The two cemented elements are the same
thickness but one has a larger diameter (barely) than the other. It is a
very sharp ortho indeed. The image I recently posted is horrible
compared to last year's best:
http://edmar-co.com/adriano/astro/As...24_collage.jpg

As far as I can tell, this ortho is definitely a plossl design. It's an
old one from about '81 and is tack sharp.

I reassebled it wrong and my magnification went down, I tried to fix it,
following the standard plossl flat-sides-out larger lens to field, but
it's all cloudy now

I'll definitely try it upside down when I get the chance.

Rick Johnson wrote:


Adriano wrote:

I have an old 9mm celestron ortho that I just took apart. All the
diagrams I've seen of eyepieces show this lens configuration as
Plossl. Are celeston orthos really plossls? It's a pair of cemented
doublets. Also, if you happen to know the order they go in, drop me a
line. I have one cemented pair slightly larger than the other, a
spacer and two baffles (one wide and one narrow).

Thanks!


Orthos I have all are a three element field lens and single eye lens.
Determining which is end of the triplet goes toward the mirror is
difficult. In theory it is the fatter of the two double convex lenses.
First time I take mine apart I put an arrow on the side pointing to the
objective. If that wears off I'm in trouble. The less convex side of
the eye lens goes toward the eye. Symmetrical or plossl are doublets.
Symmetrical are, well symmetrical so both lens pairs are the same,
convex to convex. In a plossl the field lens is often larger than the
eye lens. Also the objective side of the field lens is flat to concave
and often thicker (not by much) than the eye lens. The flat side of the
eye lens goes toward the eye. The convex lenses of each pair face each
other.

But there's so many variations out there, sounds like you have one of
those. I can't say what the Celestron version is like. We got one with
the C14 at Hyde in the mid 70's. It was awful and is never used. It was
the only ortho I ever saw that was lousy. Even some cheap ones I saw
were excellent. I've seen far better Kelners than that Celestron Ortho
we got. I never took it apart to see what was inside.

Since you are still using yours it obviously is a much improved version
than ours so likely wouldn't help to open it up. The doublet
arrangement sounds like a plossl design to me.

See this URL for diagrams.
http://www.hypermaths.org/quadibloc/science/opt04.htm

As a side note, my ortho's work best for eyepiece projection if they are
used upside down. That is, with the objective side toward the film or
CCD. I get far less curvature and edge distortion that way. But then I
never took a Jupiter as clear as the one you just posted so you're way
ahead of me!

Rick


--
Adriano
http://www.edmar-co.com/adriano/

34°14'11.7"N

"Contrary to all the evidence at hand, the entire universe is composed
of only two substances: Magic and Bull****"