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Antique Dolland London telescope -- please help

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#1 vlad0002

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Posted 23 January 2010 - 09:56 PM

Hi all,

I am new here. Someone in a different board mentioned this place as the one I should go to for help.

A day before yesterday I picked up a nice early telescope in an antique shop. It is well used, very nice condition for t's age, marked "Dolland London" in cursiv leters. The only problem with it is a missing (broken?) front element of the achromatic lens. The second element is there, ratling in the holder. I took it off and held a slightly bigger acromat from another telescope on it's place -- was able to get a picture right away, so I'm positive that's the only problem, as far as optics go.

So, the question is, how do I go about fixing this? Are there good places that sel 1 5/8" (~40-41mm) replacement acromatic 2 element lensed for such telescope? Someone mentioned www.surplusshed.com. They have some 40mm acromats, but what focal length shoul I pick? The highest they go is 465mm. Specs of the telescope are:

36-3/4" fully extended, w/o shade;
41" with shade.
20-1/2" closed.
The barrel is 2-1/2" at the thickest place.
Focal length is 927-930mm, measured from front to rear element in a fully extended state.

I would also like very much to learn more about the telescope. I searched the internet and found several similar telescopes made by Dolland, but they all looked newer, with the letters stamped, not etched cursive. Which Dolland is it (I understand, there were several) and what's the approximate date?

Sorry for so many questions -- I'm new to this. I''ve been collecting clocks for years, but was secretly allways interested in antique optics. The samples I saw before were way too expensive. This one was an odd ball for the antique dealer, so he gave it to me for $150. Could not pass that up.

I'm posting some pictures of the telescope. I put some shrinkwrap on one end to prevent the weaved cloth covering from deteriorating -- it is loose there.

Anyway, any help on this will be highly appreciated.

Thanks.

Vlad

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#2 vlad0002

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Posted 23 January 2010 - 09:57 PM

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#3 vlad0002

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Posted 23 January 2010 - 09:59 PM

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#4 vlad0002

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Posted 23 January 2010 - 09:59 PM

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#5 vlad0002

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Posted 23 January 2010 - 10:00 PM

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#6 vlad0002

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Posted 23 January 2010 - 10:02 PM

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#7 vlad0002

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Posted 23 January 2010 - 10:07 PM

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#8 vlad0002

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Posted 23 January 2010 - 10:08 PM

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#9 vlad0002

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Posted 23 January 2010 - 10:08 PM

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#10 vlad0002

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Posted 23 January 2010 - 10:09 PM

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#11 JayKSC

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Posted 23 January 2010 - 10:21 PM

Vlad,

From a collector's point of view, replacing the missing lens element will do little to help bolster your telescope's value. Since the original optics cannot be replaced, this will not enhance the value at all. For a use and completion perspective, though, this would be welcome.

With these very old telescopes, I'd recommend having a professional optical company replace the missing optics and refit them in the lens cells (assuming that your telescope has the lens cells). You should seek out a reputable company that handles fragile equipment and antiques. Having such a company do the lens replacements will not be cheap, but is the safest way to go with these classic instruments (to me). I have a telescope from a known 19th century ship wreck that has missing lenses. Museum curators and antique dealers have all told me that it's likely better to not replace the missing glass.

As for your particular Dollond telescope, it seems that it's likely circa-1800 in date. The script type signing was common to all opticians who manufactured microscopes and telescopes from the 18th century through the late 19th century. Starting around 1825, some manufacturers began using stamped letters, which became more typical than script by around 1875.

On close inspection of the script on your telescope, I'm sorry to say that you do not have an authentic Dollond telescope. The script's L is distinctly different from the circa 1800 Dollond optical shop and the second "o" on your telescope's script is clearly an "a". You have a "Dolland" telescope. It is still an antique and still dates to around 1800 by my best estimate. As John Dollond and his sons became well known opticians, many other optical shops tried to sell imitation Dollond telescopes. Your telescope is one of these imitations.

- Jay
South Florida

#12 JayKSC

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Posted 23 January 2010 - 10:25 PM

Oh... Found the info. for the optical company that was recommended to me by an antique dealer and restorer:

Maryland Precision Instrument
112 East 24th Street
Baltimore, MD 21218
410-467-1166

Again, since I decided to not restore my one telescope that has missing glass, I have not contacted this company. I got this info. back around 2001, so I don't know if Maryland Precision is still around.

- Jay
South Florida

#13 vlad0002

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Posted 23 January 2010 - 10:38 PM

Thank you very much for the info, Jay.

I realize that, about the antique value. I was thinking of just taking the unbroken element out and putting a good, although modern, achromat in. Siice this requires no alteration, it would not affect the value and can easily be undone. The place I mentioned has achromats of conparable size for $14 a piece. My consern vas getting the right focal length: the highest they have is 465mm, while mine measures ~930mm. SHould I be conserned about this difference, and is measuring in fully extended state is a correct way to determine focal lendgth in spyglasses? What will happen if I try an incorrect focal length lens?


I was just trying to get some picture out of the thing, for display purposes, mostly. If I decide to sell -- the original will go in and the new one will accopany as option (like, if you want to actually see things through the instrument).

Also, i searched for Dolland and got some hits:
"This is a large example of a 19th Century telescope by George Dolland. His real name was George Huggins, but he changed it to Dolland, the name of his famous uncle, Peter Dolland. He was born in 1774, and he was apprenticed to Peter in 1788. He took over Peter's business in 1820 when Peter died. George Dolland died in 1856, but their name is still trading under Dolland and Aitchison...."
from http://www.hubbletel...k/dolland.shtml

Thanks again.

Vlad

#14 JayKSC

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Posted 23 January 2010 - 10:50 PM

Hi Vlad,

I'm not familiar with finding the focal length of these spyglasses. This is the first I've read about George Dolland. I've not seen him listed in some of the instrument makers' databases I've used. I'm unsure of how accurate the information is on the website you provide; the text on the page you linked says that it was "John Dolland" who invented the achromatic lens which is only partly correct (not to mention wrong in name spelling).

Sorry that I lack much additional information!

- Jay
South Florida






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