Four-Draw French Naval Telescope w/Sliding Lens Shield (Ca. 1845)

This was the last antiques purchase I made before it became necessary for me to pack up all my treasures, in preparation for a big move that I had to make. I haven’t written about it yet because I’ve been sick in bed for the past few days struck down by allergies! (damn cats…!)

Anyway, now that I am sufficiently recovered, and no longer rashy and puffy (yeah it wasn’t fun…), I have decided to take some time to write about what has to be one of the finest purchases I’ve made so far, and which was partially funded by the selling-off of some of my other antiques.

I bought this from a chap at the local flea-market who went on buying trips in Europe. He’d picked this up during a visit to France, he told me. It had to be by far the most complete and perfect example I’d ever seen, and after a lot of haggling and playing of the ‘repeat-purchaser’ card, we struck a deal.

The telescope, as you can see, is a large, four-draw naval telescope, with a wooden barrel, brass fixings, and a sliding brass lens-shield, complete with the original lens-caps and shutters. Its full length is 38.5in. Engraved on the eyepiece draw-tube are the words:

Maison de
L’Ing. Chevallier, Opt’n.
Place du Pont Neuf, 15
Paris.

Roughly translated, it reads:

House of Chevallier. Optician. 
Place du Pont Neuf, 15,
Paris. 

I have researched this, and it appears that Monsieur Chevallier was a very noted French optician, producing not only telescopes, but from what I’ve seen, a lot of microscopes, as well! He was also an optician to French royalty, according to one advertisement I came across. The address, 15, Place du Pont Neuf, is in central Paris, near the River Seine (‘pont’ is ‘bridge’ in French), near to the famous Cathedral of Notre Dame!

Just picking the telescope up and moving it around in my hands told me that this was a very high-quality piece, although like a lot of antiques, it had not been restored or overhauled in decades, which meant of course, that it was jammed up with gunk, grime, and dust, and therefore, entirely seized up. There was also a significant dimple on the lens-shield, which was causing it to jam.

Restoring the Telescope

Once I got it home, I started on the usual tedious, but necessary restoration process, to prevent the telescope from being damaged any further. This included blowing out all the dust, wiping down the lenses inside and out, disassembling the entire piece and cleaning and lubricating the threads, and flushing out all the grime and grit accumulated inside the focusing mechanism and draw-tubes – which is by far the most tedious part of this whole rigmarole!

One of the more fiddly parts of fixing this telescope was removing the dent in the sliding lens-shield at the front of the barrel. The dent was not large, but it was sufficiently concentrated, and deep enough, that it kept rubbing on the protective end-stop at the end of the barrel, thereby causing the entire mechanism to jam. No amount of oil would solve this, so the dent had to be removed.

Of course, removing the entire dent was not likely to be possible, but removing enough of it to stop the jamming would be sufficient. To do this, I unscrewed the lens-shield from its coupling ring, and then slid it off the barrel over the objective lens, past the end-stop which usually held it in place. The next step was to lay the shield on a flat surface without damaging the rim on the edge (which serves as a stop-point for the lens-cap).

Once I’d done this, I needed to locate the dent. Once found, I rolled the shield so that the dent was bottom-most, and pressing against my flat surface (a solid, wooden benchtop). Then I slipped a wooden rolling pin (like what you use to make cookies with) inside the shield to act as a mandrill. Next came the tedious process of rolling, pressing, rolling, pressing, rolling and pressing, using the smooth surface of the benchtop, and the smooth, round surface of the rolling-pin to pop the dent back out.

This had to be done carefully. Too much force and I’d end up with a nice OVAL-shaped lens-shield, which wouldn’t fit back onto my telescope. Not enough force, and I’d never get rid of the dent! However, diligence paid off, and I was able to remove enough of the dimple to achieve the desired result. Rather than tempt fate, I stopped there and reassembled the telescope.

Removing, or rather reducing, the dent was the only major repair I did to this piece. The rest of it was largely just cleaning, or small cosmetic things like light polishing, cleaning the lenses and tightening up loose couplings.

What’s the point of the sliding shield?

OK, so you cleaned it, you removed the dent, you oiled it, you washed out the grime and wiped it down…but what’s the whole point of that sliding cylinder, anyway?

It’s called a lens-shield. They were pretty common on antique telescopes, both of the pocket-sized terrestrial variety, and the larger, handheld maritime variety (like this one). Their purpose was to protect the lens while the telescope was in-use. They were slid out ahead of the objective-lens, and they provided protection to the glass from things like rain, snow, and excessive sun-glare. Having the shield extended meant that when looking in the direction of the sun, the rays of light hit the shield before they would hit the lens, preventing reflective glare.

In inclement weather, the shield kept rain, condensation and snow off of the lens, so that you didn’t have to keep wiping the glass every few seconds, thereby providing you with an unobstructed view – very important when you might be on the deck of a ship in the middle of a heavy storm!

Interesting Notes on Construction

I’ve seen a fair few antique telescopes in my time, ever since I started getting interested in antique optical stuff, about eight to ten years ago. While most telescopes from the 1840s-1850s up to the 1930s, 40s and 50s were all basically made the same way, with the same components and methods of construction, there were elements of this telescope which the manufacturer included which just make me love it just that little bit more.

The first element was the way the lens-shield was attached to the barrel of the telescope. On all other telescopes of this type that I’ve seen, to remove the shield, you need to pull apart the barrel and slide the shield backwards off of the body of the telescope. It’s fiddly and annoying. With this telescope, the shield is screwed onto a threaded coupling-ring that slides up and down the barrel. You simply unscrew the shield from the ring, and then you can slide the whole thing off the telescope, without having to disassemble anything!…You don’t even have to take off the lens-cap, if you don’t want to! This makes cleaning and overhauling this particular telescope much easier!

The second element about this telescope’s construction that I really liked was the inclusion of tiny holes which were drilled into each draw-tube, at the points where their coupling-rings screw together. I’d never seen anything like this on other telescopes before, and this confused me at first. It wasn’t until after I’d cleaned, polished, and de-grimed the entire instrument that their purpose was revealed to me, since only then would their function be fully understood!

So why on earth would you have tiny pinholes drilled into the draw-tubes of a telescope? The simple answer is air-pressure!

Telescopes, for all their simplicity of construction, actually have components that fit together with remarkable precision. Every lens, every rim, every coupling-ring, every tube and cartridge, slips, slides and screws together in a very precise, tight-fitting way. To ensure smooth action, and to ensure that the telescope will not pull apart accidentally, the tubes and the coupling-rings, lenses and everything else, are fitted together with almost microscopic tolerances, so much so that the whole thing is virtually airtight!

The result of these tight-fitting parts is that when the telescope is collapsed for storage, there’s a lot of air trapped inside the draw-tubes which despite their snug fits, are obviously, not airtight. On small telescopes, this air can easily be forced out of the microscopic gaps between the draw-tubes, but on larger telescopes where this might not be possible, collapsing the telescope in the sharp, brisk, business-like manner that most people might’ve seen in TV shows or movies, just wouldn’t be practical, or probably, possible!

Here, you can see the three holes (on the left) drilled into the draw-tubes, with the maker’s details engraved on the right.

The holes in the draw-tubes therefore serve as air-pressure valves. The give the air somewhere to go when the tubes collapse into each other and force the air inside them out of the telescope. They make the process of opening and closing the telescope much smoother and easier. Without them, the resistance caused by the trapped air would likely make the draw-tubes jam or stick, both in opening, and closing the telescope.

Concluding Remarks

This concludes this latest posting, and my examinations of this latest addition to my collection. While other pieces may come and go, I’m pretty certain that this one will be a lifelong keeper. It really is an excellent piece and in such fantastic condition. There are a few minor blemishes that’s true, but you’d have a few yourself if you were nearly 200 years old!

Now all I need is a round-the-world cruise on which to bring it, so that I can do a spot of touristy sightseeing through its lenses, from the high, clear vantage point of the boat-deck of some grand ocean-liner… Eh…one day!

 

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