No thanks - I'll save my money

erick (Eric) · #1 29-10-2009, 04:40 PM

Just scanning the ebay scopes. How about this beauty? Starting bid $2,500.

The seller says:- "The controls and optical performance are in very good operating condition except that the refecting disc at the top of the cylinder is missing."

Yes, I think the absence of the objective lens of a refractor might devalue it a little.

http://cgi.ebay.com.au/GEORGIAN-REFE...item414a0c463c

Omaroo (Chris Malikoff) · #2 29-10-2009, 04:43 PM

Quote:

Originally Posted by erick

Yes, I think the absence of the objective lens of a refractor might devalue it a little.

I think he/she is talking about the secondary Eric. It's a reflector, not refractor.

erick (Eric) · #3 29-10-2009, 04:51 PM

Sure looks like an eyepiece sticking out the back.

Maybe "refecting disc" is having a bet both ways?

ngcles · #4 29-10-2009, 05:01 PM

Hi Erick, & All,

Yep, as Chris said, this is a Gregorian reflector and based on the pics looks pretty genuine. This is quite similar, if not identical to the type and size of 'scope used by Cook and Greene to observe the transit of Venus in 1769 at Tahiti (before their voyage went on to New Zealand & Australia).

Hard to say how they can say "optical performance are in very good operating condition" when it clearly has no secondary and cannot form an image. I wonder if any light can be shed on its history?

The starting price, all things considered ,seems very good value. We have an almost identical telescope on display at Sydney Observatory that was purchased at a London Auction house in 2002 for a somewhat higher sum -- but it is is better condition and is at least capable of being viewed through. It was purchased to be part of the Transit of Venus exhibit.

Best,

Les D

TrevorW · #5 29-10-2009, 05:03 PM

Erick

It could be that it's a Gregorian not a georgian telescope a word can make the difference

http://chem.ch.huji.ac.il/history/adamsg.html

Cheers

ngcles · #6 29-10-2009, 05:05 PM

Hi Erick & All,

Quote:

Originally Posted by erick

Sure looks like an eyepiece sticking out the back.

Yep

Exactly where it ought to be !

http://en.wikipedia.org/wiki/Gregorian_telescope

Its design actually pre-dates the Newtonian but I don't think Gregorian reflectors have been manufactured commercially for about 150 years.

Best,

Les D

erick (Eric) · #7 29-10-2009, 05:14 PM

Well, as I've said before, I learn new things every day. Thanks gentlemen.

Still think I'll save my money to pay for my coming SDM.

pgc hunter · #8 29-10-2009, 06:46 PM

"reflecting disk" lololol

2.5 grand and the reflecting disk is missing? How am I 'sposed to see teh flag on teh moonsk like that????

Yeah my 2.5 grand can go to way better stuff...

Kal (Andrew) · #9 29-10-2009, 07:13 PM

Is this the same telescope that the powerhouse museum in Sydney has? If so it is a genuine piece of history, and difficult to put a value on

http://www.powerhousemuseum.com/coll...se/?irn=351807

ngcles · #10 29-10-2009, 08:23 PM

Hi Andrew & All,

Quote:

Originally Posted by Kal

Is this the same telescope that the powerhouse museum in Sydney has? If so it is a genuine piece of history, and difficult to put a value on

http://www.powerhousemuseum.com/coll...se/?irn=351807

As I noted in an earlier post above, it is very similar and assuming the "Circa 1780" date is correct is likely older. The one at the PHM (Sydney Observatory) is shown better at this link:

http://www.sydneyobservatory.com.au/...thor=4&paged=3

about 1/5th the way down the page.

The one we have is of slightly larger aperture (just over 3") and probably longer focal length (the tube is a little longer) but is otherwise of identical design and by the same manufacturer.

This one might be a significant telescope -- it's hard to tell. I have alerted Nick Lomb (my boss at Sydney Observatory) as it may be of interest to the PHM and it would be a good thing to investigate whether it may or may not have a "colourful" history. A history or lack of it could affect its value considerably and as you say, it is difficult to put a value on. On face value, given the blurb, the seller has little idea about telescopes so ...

As noted above, the example we have at Sydney Observatory was purchased at Sotherby's in 2002 and I pretty sure we paid somewhat more than the starting price for this example.

That said, the one we have is in better condition, has a secondary and is capable of functioning as a telescope (I haven't looked thorugh it though).

Hope that clears it up.

Bid or refrain from bidding at your own discretion/risk!

Best,

Les D

Outbackmanyep · #11 29-10-2009, 08:30 PM

Item location is in Adelaide, why not get someone from a Uni there to check it out??

DavidU (Dave) · #12 29-10-2009, 08:36 PM

It wouldn't be that difficult to get a paraboloid secondary made for it???!!

ngcles · #13 29-10-2009, 09:21 PM

Hi David & All,

Quote:

Originally Posted by DavidU

It wouldn't be that difficult to get a paraboloid secondary made for it???!!

It needs a concave ellipsoidal secondary. To retain the integrity of the instrument, it should be made of speculum metal like the primary (not glass).

Not impossible by any means but certainly not something you'd buy off the rack ...

Satchmo might be able to comment on the ease or difficulty in obtaining the materials and/or fabrication? Maybe this mob will make you one ?

http://www.interspectrum.ee/off-axis.html

However, you wouldn't restore this telescope to look through (except perhaps for occasional "wind-in-the-hair motoring". The view would be pretty average compared to virtually all the gear people here own. After some TLC, it really belongs in a glass cabinet.

Best,

Les D

DavidU (Dave) · #14 29-10-2009, 09:48 PM

Sorry yes, a concave ellipsoid. My memory does not serve me well.

Quote:

Originally Posted by ngcles

Hi David & All,

It needs a concave ellipsoidal secondary. To retain the integrity of the instrument, it should be made of speculum metal like the primary (not glass).

Not impossible by any means but certainly not something you'd buy off the rack ...

Satchmo might be able to comment on the ease or difficulty in obtaining the materials and/or fabrication? Maybe this mob will make you one ?

http://www.interspectrum.ee/off-axis.html

However, you wouldn't restore this telescope to look through (except perhaps for occasional "wind-in-the-hair motoring". The view would be pretty average compared to virtually all the gear people here own. After some TLC, it really belongs in a glass cabinet.

Best,

Les D