Celestron Ultima 100

I recently bought a fixed eyepiece for a Celestron Ultima 100 . The
eyepiece is a standard 1.25" Plossl which I believed would fit the
Celestron. When I tried to fit it to the telescope I discovered it is very
slightly too big to fit into the mount. My local Celestron dealer said he
has heard of this before but doesn't know if there is a special adapter for
these eyepieces. Yet on some forums on line I hear people have used fixed
lenses in their Celestrons before. Having measured the sizes I would say a
simple 35 mm to 30 mm adapter ring would do the job very well. Has anyone
here had this problem? Is there a special adapter I can buy somewhere?
Or perhaps someone has discovered their own personal work around for this
problem?

I'd appreciate any help.

Thank you.

omega

On 01/05/2011 12:36, Omega wrote:
I recently bought a fixed eyepiece for a Celestron Ultima 100 . The
eyepiece is a standard 1.25" Plossl which I believed would fit the
Celestron. When I tried to fit it to the telescope I discovered it is very
slightly too big to fit into the mount. My local Celestron dealer said he
has heard of this before but doesn't know if there is a special adapter for
these eyepieces. Yet on some forums on line I hear people have used fixed
lenses in their Celestrons before. Having measured the sizes I would say a
simple 35 mm to 30 mm adapter ring would do the job very well. Has anyone
here had this problem? Is there a special adapter I can buy somewhere?

An adaptor will only work if the scope has enough back focus to allow
the image to be focussed. You should be able to test if this is
physically possible by holding the new eyepiece up against the hole and
looking at a distant object with it. If you can still obtain focus at
infinity then an adaptor is possible. Test this before investing any
money in obtaining an adaptor...

You might be able to bodge something out of plastic plumbing parts for a
quick test of concept.

Or perhaps someone has discovered their own personal work around for this
problem?

I'd appreciate any help.

I don't know it they do one, but SRB-Griturn have always been a good
source of awkward threaded photographic adaptors, fliters connectors and
are usually game to make custom things that might be popular.

http://www.srb-griturn.com/

Mostly photographic, but they are sympathetic to astronomers requests.

Regards,
Martin Brown

Thank you Martin. I have unscrewed the barrel from the eyepiece and then
the eyepiece will sit in the mount albeit loosely. It focuses perfectly
while I hold it down with room to spare for a thin 'ish adapter if I can
find one. Obviously I can 'make' it sit in the mount more secure with
perhaps a few twists of tape but I'd like to see a proper job with an
adapter when I start swapping lenses in the dark. I'll try get hold of
your firm after the holiday.

omega



"Martin Brown" wrote in message ...

On 01/05/2011 12:36, Omega wrote:
I recently bought a fixed eyepiece for a Celestron Ultima 100 . The
eyepiece is a standard 1.25" Plossl which I believed would fit the
Celestron. When I tried to fit it to the telescope I discovered it is very
slightly too big to fit into the mount. My local Celestron dealer said he
has heard of this before but doesn't know if there is a special adapter
for
these eyepieces. Yet on some forums on line I hear people have used fixed
lenses in their Celestrons before. Having measured the sizes I would say a
simple 35 mm to 30 mm adapter ring would do the job very well. Has anyone
here had this problem? Is there a special adapter I can buy somewhere?

An adaptor will only work if the scope has enough back focus to allow
the image to be focussed. You should be able to test if this is
physically possible by holding the new eyepiece up against the hole and
looking at a distant object with it. If you can still obtain focus at
infinity then an adaptor is possible. Test this before investing any
money in obtaining an adaptor...

You might be able to bodge something out of plastic plumbing parts for a
quick test of concept.

Or perhaps someone has discovered their own personal work around for this
problem?

I'd appreciate any help.

I don't know it they do one, but SRB-Griturn have always been a good
source of awkward threaded photographic adaptors, fliters connectors and
are usually game to make custom things that might be popular.

http://www.srb-griturn.com/

Mostly photographic, but they are sympathetic to astronomers requests.

Regards,
Martin Brown

On 01/05/2011 17:59, Omega wrote:
Thank you Martin. I have unscrewed the barrel from the eyepiece and then
the eyepiece will sit in the mount albeit loosely. It focuses perfectly
while I hold it down with room to spare for a thin 'ish adapter if I can
find one. Obviously I can 'make' it sit in the mount more secure with
perhaps a few twists of tape but I'd like to see a proper job with an
adapter when I start swapping lenses in the dark. I'll try get hold of
your firm after the holiday.

The other option is to find your local model engineering club and talk
nicely to them. Someone with a lathe might be prepared to make you a one
off for the cost of materials and a nominal charge. You might even find
a standard stock aluminium tube of the right diameter on eBay.

Regards,
Martin Brown

On 02/05/2011 11:10, Martin Brown wrote:
On 01/05/2011 17:59, Omega wrote:
Thank you Martin. I have unscrewed the barrel from the eyepiece and then
the eyepiece will sit in the mount albeit loosely. It focuses perfectly
while I hold it down with room to spare for a thin 'ish adapter if I can
find one. Obviously I can 'make' it sit in the mount more secure with
perhaps a few twists of tape but I'd like to see a proper job with an
adapter when I start swapping lenses in the dark. I'll try get hold of
your firm after the holiday.

The other option is to find your local model engineering club and talk
nicely to them. Someone with a lathe might be prepared to make you a one
off for the cost of materials and a nominal charge. You might even find
a standard stock aluminium tube of the right diameter on eBay.

Just remembered a couple of other places that might be worth a try for
small engineering bits so will tack them onto this thread:

AWR Technology (Astroparts)
http://www.awrtech.co.uk/awr_info.htm

BC&F AstroEngineering
http://www.astro-engineering.com/cat...ors/index.html

Hope you can find the right bit!

Regards,
Martin Brown

"Martin Brown" wrote in message ...

On 02/05/2011 11:10, Martin Brown wrote:
On 01/05/2011 17:59, Omega wrote:
Thank you Martin. I have unscrewed the barrel from the eyepiece and then
the eyepiece will sit in the mount albeit loosely. It focuses perfectly
while I hold it down with room to spare for a thin 'ish adapter if I can
find one. Obviously I can 'make' it sit in the mount more secure with
perhaps a few twists of tape but I'd like to see a proper job with an
adapter when I start swapping lenses in the dark. I'll try get hold of
your firm after the holiday.

The other option is to find your local model engineering club and talk
nicely to them. Someone with a lathe might be prepared to make you a one
off for the cost of materials and a nominal charge. You might even find
a standard stock aluminium tube of the right diameter on eBay.

Just remembered a couple of other places that might be worth a try for
small engineering bits so will tack them onto this thread:

AWR Technology (Astroparts)
http://www.awrtech.co.uk/awr_info.htm

BC&F AstroEngineering
http://www.astro-engineering.com/cat...ors/index.html

Hope you can find the right bit!

Regards,
Martin Brown


I've sent an email off to AE as they look quite promising and also mailed
one or two others. Will let you know if I get a part or not, in due
course. Thanks for the links.


omega

"Martin Brown" wrote in message ...

On 02/05/2011 11:10, Martin Brown wrote:
On 01/05/2011 17:59, Omega wrote:
Thank you Martin. I have unscrewed the barrel from the eyepiece and then
the eyepiece will sit in the mount albeit loosely. It focuses perfectly
while I hold it down with room to spare for a thin 'ish adapter if I can
find one. Obviously I can 'make' it sit in the mount more secure with
perhaps a few twists of tape but I'd like to see a proper job with an
adapter when I start swapping lenses in the dark. I'll try get hold of
your firm after the holiday.

The other option is to find your local model engineering club and talk
nicely to them. Someone with a lathe might be prepared to make you a one
off for the cost of materials and a nominal charge. You might even find
a standard stock aluminium tube of the right diameter on eBay.

Just remembered a couple of other places that might be worth a try for
small engineering bits so will tack them onto this thread:

AWR Technology (Astroparts)
http://www.awrtech.co.uk/awr_info.htm

BC&F AstroEngineering
http://www.astro-engineering.com/cat...ors/index.html

Hope you can find the right bit!

Regards,
Martin Brown



Several of my enquiries drew a blank with most correspondents never heard of
such an adapter. The firm you mentioned in your first reply say on their
site, they will make to spec' but I noted their start price was £50 plus VAT
then postage. I have been in touch also with the Celestron importers and
they say my particular model was never intended for fixed eyepieces. One
dealer though informed me that Acuter fixed lenses will fit as they share
the same size collar as the Celestron zoom lenses for the Ultima. But
again, I discovered they are twice as dear as a good quality Plossl from
Ebay. So I've hung my holsters up on this one for the time being at least.
As a matter of interest, the new Celestron 'Regal' range will take a common
Plossl 1.25" fixed lens. Great I hear you all say but they are LOT of
money in the first place. Truthfully I'm happy with the clarity of the
Ultima but I do love me gadgets and a couple of Plossls sounded great at the
time. Thanks for the links, at least I'm a little wiser now.

Omega