I love antique telescopes, I just think they’re so cool. Their construction, their beauty, their intricacy, and the levels of embellishment put into their design. I’ve always had an interest in all antique optical equipment because of my poor eyesight, but there’s a romance about telescopes that you just don’t get with binoculars. They make you think of ships at sea, people on clifftops looking out over the coast, of trekking across the countryside, and the mysterious, far-off places which they’ve seen.
In this posting, I’m looking in detail at antique telescopes. A bit about their history, their construction, repair, refurbishment, etc. So polish your eyepieces and hold onto your lens-caps…
Antique Telescopes: The Basics
There are two basic types of telescopes which most people will be familiar with: The refracting telescope, and the reflecting telescope. The refracting telescope uses lenses of glass, whereas the reflecting telescope uses finely-polished mirrors. In this issue of TAT Antiques, I’ll be covering the more common refracting telescope, as this is the kind that you’re most likely to come across in antiques shops and flea-markets.
So, what do you need to know about antique telescopes?
Antique Telescopes – Context and History.
In an age before aircraft of any kind beyond a hot-air balloon, all travel beyond shore, and all delivery of cargo beyond shore relied on sailing ships and steamships. Before GPS, RADAR, satellites and transponders, mariners relied on maps, compasses, chronometers and sextants to find their way around the world. However accurate these aids might’ve been, arguably the most important maritime aid was the refracting telescope. Knowing where you were supposed to be, or where you had to go, or simply identifying where you were at all, was almost impossible without a telescope. Mariners needed powerful, long-distance vision-aids to help them scan everything from far-off flags, cliffs, hills, buildings, and other ships as they sailed around the world.
A Georgian-era telescope from the 1730s.
For all these reasons, from the 1600s up to the mid-20th century, telescopes were actually pretty important, and they were made by a wide range of manufacturers. Telescopes could see things great distances away, and with impressive clarity, important when you’ve sailed halfway around the world, and you’re trying to identify the harbour that you’re meant to dock at, which might be several dozen meters away. Mariners prized the telescopes, and on any given ship, they would’ve been among the most important and treasured possessions owned by the common sailor.
Telescopes were seen as the badge of office for sea-captains, admirals and naval officers, and such officers and captains might even receive telescopes from their colleagues as rewards for heroic deeds, tokens of good esteem, or presents to mark important events. In such instances, details of the deed or event which warranted the presentation of a telescope (which would’ve been an expensive item in its day!) would’ve been handsomely engraved on the barrel or draw-tubes of the telescope, as a form of commemoration.
The invention of the refracting telescope is generally attributed to famous Italian astronomer and engineer, Galileo Galilei, in the early 1600s. Whether or not this is true is up for some debate – chances are he probably invented the first one which was any good – as is often the case with great inventions – like the telephone, automobile and telegraph – great inventions can rarely be attributed to just one person.
At any rate, throughout the 1600s, from the time of Galileo, other inventors took his basic design and improved on it. Early telescopes were far from perfect – the images were often blurry, or even flipped upside down by the lenses! Knowing what type of lenses to use, and in what sequence they had to be placed would be worked out over the next century or so, until quality telescopes capable of clear views were developed.
Really early telescopes, such as those from the later 17th and early 18th century differed greatly from those of later decades in that they were much, much, much larger! The manufacturing limitations of the time meant that they could be several feet long, and quite heavy! It wasn’t until the later 1700s that collapsible telescopes which were more compact and also more powerful, were possible.
Although they were primarily used at sea for navigation, spotting landmarks, reading signals and sighting far-off, potential dangers to the ship, telescopes were also used on land, both in warfare, and for recreation. Field commanders used them in battle to watch the progress and direction of combat and to direct troops, and people used them for sightseeing, birdwatching and other leisure activities. How these telescopes all differ will be covered later on.
Antique Telescopes – Materials and Construction
From their earliest days, right into the second half of the 20th century, the vast majority of telescopes – almost all of them – were made of brass. Brass tubing, brass coupling-rings, brass rims for the lenses, brass screws and fixtures and brass lens-shutters and caps. The decision to use brass was twofold – for one thing, brass was relatively cheap. For another, brass did not corrode or rust like other metals might. This made it ideal as the metal from which to make telescopes, which might spend years and decades at sea, surrounded by moisture, humidity and saltwater.
The barrels, rims, coupling-rings, draw-tubes and other components of a telescope were all made of brass and the lenses were made of glass. But antique telescopes often had another component in their construction, and that was the barrel-cladding.
The barrel is the main body of the telescope. To make it easier and more comfortable to hold for long periods of time, the brass tubing was often clad in another material. This would stop the hand from slipping on smooth metal and provide better grip, and would also stop your fingers freezing to the brass if the weather was particularly cold. Popular coverings included thin sheets of Morocco leather, and various types of wood. Wooden blocks were spun on a lathe and rounded off, then bored out into a tube and slipped onto the brass barrel before being either screwed, riveted or glued into place. Mahogany and rosewood were popular.
One reason why telescopes were more popular than more compact binoculars was because telescopes were much more powerful. Most telescopes had up to half a dozen different lenses inside them, which magnified and clarified the image, as well as kept it steady, with minimal distortion from light. These series of lenses were screwed into double-ended cartridges or rims which could then be slotted and screwed into the telescope.
To clean the lenses, one simply unscrewed the telescope, unscrewed or slid out the cartridges, unscrewed the lenses, cleaned them, and then screwed and slotted everything back together. Since everything could only go back together in one very specific way, the chances of accidentally mixing up the lenses was minimal. Telescopes were expensive and were expected to last for many years. For this reason, they were really designed to be user-friendly, and easily maintained.
Some of my antique telescopes. The largest is also the oldest – from about 1850.
Many antique telescopes came with friction-fitted lens-caps over the large objective lenses, and usually – sliding lens-shields over the eyepiece. Older telescopes had sliding lens-shutters over both the front and back lenses, similar to guillotine blades, whereas more modern ones had detachable lens-caps on the fronts, and sliding lens-shutters on the back. This is one way to guess roughly how old a telescope is, as sliding shutters front-and-back became less common as time went on.
From the late 1700s right up to the middle part of the 1900s, how refracting telescopes were made (and indeed, how they’re still made today) hardly changed at all. The materials and finishes might have come and gone and changed with the times, but in essence, a telescope was made of drawn out brass tubes with threaded coupling rings, a barrel, glass lenses and brass lens-caps and shutters to protect the glass.
Because of this, it can actually be surprisingly difficult (and in many cases, impossible) to tell how old an antique telescope is. One made in 1770 would in all likelihood, be indistinguishable from one made in 1880, which would look very similar to one made in 1920 or 1930. There are subtle ways of guessing how old a telescope is, and I’ll cover that later on.
Different Types of Antique Telescopes
Antique refracting telescopes came with a surprising array of features and design-variations. The most basic ones simply slid out and back and had lens-shutters or caps at each end. However, there were differences and nuances.
Smaller telescopes (approx. 6-8in closed lengths) were typically sold as pocket telescopes. They were designed to fit into a jacket or trouser pocket for someone who might ride on horseback, who went hiking, or for someone who simply wanted a smaller, more compact spyglass.
Some telescopes were sold with sliding shields that extended beyond the end of the barrel, over and around the large objective lens at the front of the telescope. Such shields were typically three or four inches long, and were meant as sun-shields or rain-shields. Their purpose was to keep sun-glare off the lens, and to keep rainwater off the glass in instances where the telescope might be used in inclement weather.
Maritime or naval telescopes were much larger than pocket telescopes. A pocket telescope was typically 6-8 inches closed, stretching out to about 15-20 inches at its fullest extension. By comparison, a larger naval telescopes, which had to see much further distances, had larger, more powerful lenses installed in them. They would measure up to 10 or 12 inches closed, and might extend to over a meter when fully opened!
Occasionally, you’ll see a telescope on a tripod or stand. These can range from small tabletop ones, to much larger floor-models. What are they?
These are called library telescopes. Their design dates back to the days when gentlemen astronomers in country houses pursued stargazing as a hobby. They were designed to stand on a table, or on the floor near a large window in your library or study (hence the name). The tripod held the telescope absolutely steady so that the viewer could scan and track the heavens, looking for stars, constellations, the phases of the moon, or distant planets in the far distance.
They’re impressive, but beyond these applications (or scanning the bounds of one’s vast country estate, or looking out to sea from your lighthouse or seaside home), they’re not especially practical these days.
One device which most people probably don’t think about when they think of telescopes is the sextant – and yes, I do mean that curved navigational instrument – but yes, even that has a telescope built into it. Granted, sextant telescopes were not especially strong (they’re only meant for looking for the sun, after all), but they are telescopes nonetheless.
The sextant was invented in the 1700s as an instrument for determining latitude (north-south position), and in this, they work pretty effectively. To operate a sextant at sea, you waited for the noonday sun to be high in the sky. You sighted the sun through the telescope, and then pulled a lever on the side of the sextant. The lever adjusted the position of a mirror built into the frame of the sextant.
You pulled on the lever until the reflected sun was level with the horizon. When this was achieved, it meant that the angle between the sun and the horizon had been calculated. Then, you simply checked the lever to see what angle it had stopped at, and this gave you the angle of the sun above the horizon. From this, you could calculate where you were.
Sextants became extremely popular in the 1800s and 1900s. Provided that the sea was calm and the sky clear, they were relatively easy to use. Their use lasted for so long because they were basically failsafe. Even today, they’re still one of the most reliable navigation devices to use at sea, two hundred years after they were invented.
Last but not least, we have day/night telescopes, and their name directly reflects their function – they’re designed to be used both day, and night! Now all telescopes can be used during the day, but what makes a night telescope?
As I said earlier – everything we see is a result of rays of light reflecting off of an object. The more light we see, the more reflection, the more object. To this end, a night-time telescope (for example, those used in stargazing) differs from a daytime telescope in that it is usually much larger, both in length and lens-size. The larger the lens, the more light you can capture, the more stuff you can see. This is why those astronomical telescopes at observatories are so massive!
The Anatomy of a Telescope
Your basic antique refracting telescope, of the kind that you’re likely to find at most flea-markets and antiques shops has a surprising number of parts! Knowing what they are and how they operate is important to knowing how to clean, fix and use your telescope. So, what are they?
The barrel is the main body of the telescope. Depending on age, it will be clad in either leather, or wood. Most antique telescopes will have a ridge at the front of the barrel. This ridge or lip is there to catch the lens-cap when you slide it on to protect the objective lens from dust, chips, cracks, and scratches.
Extending out from the barrel are the draw tubes. Most antique telescopes will have three draw tubes, some will have two, some will have four, some will have half a dozen or more! The number of tubes is how you describe what the telescope is. So if your telescope has four draw tubes, you’d describe it as a four-draw refracting telescope.
Between each draw tube, and between the main draw tube and the barrel, you will have couplers or coupling rings. These couplings are what hold the draw tubes together. They screw in and out and stop the tubes from sliding apart. You unscrew these to pull the telescope apart for cleaning.
At the back of the telescope is the eyepiece cover. This is usually just a threaded lens-cap screwed over the eyepiece lens, usually with a small, sliding shutter built into it. This is to keep dust and grit out of the eyepiece lens.
Immediately in front of the eyepiece cover is the eyepiece cartridge. This is a tight-fitting tube inside the smallest draw tube of the telescope. You should be able to just pull it right out (some telescopes might have you unscrew this to get it out). The tube will have two lenses in it that will magnify the image coming down the tubes.
At the other end of the smallest draw tube, opposite to the eyepiece cartridge is the erector cartridge. Now this one DOES screw into the tube (because the lens-rim also doubles as an end-stop for the first coupler) so be careful when you try and pull it out for cleaning! Again, it’s a brass tube with two lenses in it. These two lenses are the erector lenses, meaning that they flip the image seen through the objective lens, the right way up.
Right at the front of the telescope, you have the objective lens. This is the one that captures all the sunlight. On all but the earliest telescopes, the objective lens will almost always be what’s called an achromatic lens – that is, one lens made out of two parts. The reason for this is to sharpen clarity and improve focusing, and also to prevent what’s called ‘chromatic aberration’. Basically, two lenses help to sharpen the focus, and bring all the rays of light to a single point. If you only had one lens, the rays of light would all focus at different points inside the telescope, and you’d end up with a blurry image.
The finder scope is something that you occasionally get on larger, tripod-mounted library telescopes. It’s the little baby telescope that’s sitting on the top of the main telescope. These little fellows are low-powered telescopes with wide fields of view. They’re used to search for an object in the far distance (to find them, as the name suggests), and the object, once being found, could then be viewed more easily through the main telescope (which is mounted directly underneath).
Telescopes: Care and Cleaning
You just bought your first antique telescope! Oh boy! You can finally live out your pirate fantasies, or go to sea on your rich friend’s yacht, or go birdwatching or stargazing after sundown. But, being a newbie at this, you perhaps bought your telescope without really thinking about how to look after it…woops! Now what?
Don’t worry, this chapter is all about how to clean and maintain your beautiful new antique telescope.
The good thing about antique telescopes from the 1700s and 1800s is that they were really designed to be user-friendly. For the most part, lenses, barrels, couplings and other parts can all be unscrewed, cleaned, polished and reassembled relatively easy. But there are some things which aren’t covered in the care-and-feeding manuals!
To service and clean your antique telescope, you will need:
- One bottle of sewing machine oil, or a can of WD-40
- Tissue-paper, toilet-paper or paper-towels
- Brasso metal polish.
- Rubber gloves (optional).
- Small, flathead screwdriver (optional).
- Masking tape (optional).
These things should be all you need to get your telescope working great again, provided of course, that there is no damage to the body, the barrel, tubes or lenses. So, how does this work?
Step One: Cleaning the Lenses
To begin at the beginning – you should first clean all the lenses. On the vast majority of telescopes, these will simply unscrew from their housings, and you can simply pop them out and clean them with a damp tissue to remove any grit and dust. Make sure you clean the lenses inside and out, and be really thorough – all it takes is one tiny speck of dust to interfere with the optics of your telescope, so you want to blow out or wipe off any grit and grime that you see. Once this is done, carefully screw the lenses and their housings back into the telescope.
Step Two: Cleaning the Draw Tubes
This is one of the most important cleaning jobs that you can do on your antique telescope – cleaning the draw tubes. I will warn you now that it will take a lot of time, a lot of effort, and that if you don’t do this thoroughly, you can seriously damage your telescope.
Antique telescopes are made of brass. Brass rims, brass bodies, brass tubes, brass coupling-rings. Brass is everywhere. Brass was used because brass did not rust or corrode easily and it was easy to clean. But the problem was, brass is shiny, and manufacturers didn’t want light bouncing around inside shiny brass tubes in their telescopes. The reflections would drive you nuts! To stop this, they painted the insides of the draw tubes with a cheap paint made from lamp-black – basically, the soot that builds up inside the glass chimneys of old-fashioned oil-lamps.
Now over time, this sooty coating crumbles away. It’s caused by constantly opening and closing the telescope, as well as just by time and wear. Combine this with the fact that telescopes are not air-tight, and the tubes of your telescope will pretty quickly fill up with gunk and dust. This acts as an abrasive and creates friction. If you do not clean out all this gunk, then the dust will cause your telescope to jam when you try and focus it. And if you try and force the telescope to move, you stand a very good chance of breaking the coupling ring and ripping the telescope in half – and this would be nigh impossible to repair.
To prevent this, and to make the telescope easier to use, you need to clean out all this gunk. The easiest way to do this is to simply open the telescope to its fullest extent, and then drip or spray oil up and down the draw tubes. Then close the telescope, twisting and turning as you go, to distribute the oil all around the tubes. Then pull the telescope open, twisting and turning as you go. Repeat this several times and then using a tissue or paper towel, wipe off the oil. And then stare in shock and disgust and the black, oily grime that comes away in your hands. This is the gunk that is jamming your telescope. You must repeat this process until all the grime is gone, and the paper comes out clean.
In some cases, this may involve completely disassembling the telescope right down to its component parts to clean out the grime. This is not a process that you can rush, and it is not one that you can skip – because if the telescope jams and you try and unjam it with an overenthusiastic tug, you could very well damage it irreparably.
Once the tubes have been thoroughly cleaned and wiped down, the telescope should open and close fast and smooth – You should hear a sharp, smooth clicking sound as the tubes extend and collapse. This is the sound of the coupling rings snapping into place against the end-stops of each draw tube.
Step Three: Fixing Worn-Out Couplers
Some telescopes – not all, but some – suffer from worn out coupling rings. Every draw tube comes with a coupling-ring and an end-stop. The coupling ring slides over the tube and down to the end-stop. The ring has corrugations on it to help unscrew it, and it has threads on it, which connect it to the next draw tube in the sequence. On some telescopes, these threads can get worn out from years of screwing and unscrewing for cleaning and maintenance.
One way of repairing this is to unscrew the worn out coupling ring and wrap masking tape around the threads. This builds up a very thin layer of paper over the threads, which will provide the friction and grip necessary for the thread to bite, and hold, and stop coming apart! Now masking tape is the cheap solution – if it doesn’t work, you can go to your local hardware shop and buy threading tape which is specifically designed for sealing loose threads (they use it in plumbing to stop leaks). Whether you use painter’s masking tape, or plumber’s threading tape, the important thing to remember is to apply the tape smoothly over the threads. Any folds, kinks or twists in the tape will cause the threading to jam, and then you’ll be in real trouble!
Step Four: Fixing Jammed Couplers
Just as how coupling rings can get worn out, they can also get stuck! It isn’t uncommon on antique telescopes for coupling rings, lens-housings and other threaded components to get stuck and jammed on. This is usually because nobody cleaned it for decades, and the dust and grime got into the threads and the friction is so bad that you simply can’t unscrew it!
To get over this, simply drip in a couple of drops of sewing machine oil. Let the oil seep into the threads – put in a couple of drops all the way around and let it dribble inside. Then, with a firm grip, simply twist the threads open. If you’re still having trouble, use rubber gloves to provide extra grip.
Having opened the threads, make sure that you add more oil, to the threads and then wipe it clean with tissue-paper! Again, you’ll get the same, black, oily gunk that came out with the draw tubes. Once you’ve unjammed all the threads, you should clean out all the grime before screwing them back in, to prevent them jamming in the future.
Step Five: Polishing the Brass
The last step is optional, but it’s the process of polishing the brass on your telescope – which is basically everything that isn’t glass, or leather! Despite what you might think, polishing antique brass is perfectly acceptable, and in some cases, even necessary, although for the most part, it’s largely to do with aesthetics and visual appeal. It is up to you, but most collectors and sellers of antique telescopes that I’ve come across would prefer their telescopes polished, rather than dulled. It just looks that much more awesome.
Antique Telescopes: Storage and Usage
So, you’ve bought yourself a beautiful antique telescope. You’ve pulled it apart, cleaned it and wiped down the lenses. Now how do you use it? And once it’s been used, how do you store it?
To use your telescope, slide off the lens-covers on both ends and then pull it out to its fullest extension. Hold it up to your eye and look through it. Does everything look all blurry in the distance?
Of course it does, that’s because you haven’t focused it! Provided you’ve cleaned out all the gunk inside the telescope, and the tubes are sliding smoothly, focusing your telescope will be really easy. Simply slide the smallest draw tube into the one ahead of it. Eventually, the distance between the lenses will sync up, and the image will come into focus. The other tubes will remain stationary. In most cases, focusing the telescope to view things further and further afield will simply be a matter of sliding the first draw tube back and forth to find the ‘sweet spot’ for each different distance.
Storing Your Telescope
Once you’re done using your telescopes, to protect the lenses, make sure you slide the shutters and caps back on (if the telescope came with them, that is – most will not have their original objective-lens caps). Ideally, you should stand them upright when you’re not using them. This will stop dust getting on the objective lens, and will also stop the telescope from rolling off of any shelves or tables that you decide to display them on.
Researching Your Telescope
So, you just picked up an antique telescope. Maybe it was at auction, maybe at the flea-market, maybe from an antiques shop or from some place on the world wide web! However you got it, you have it now, and you suddenly realise you don’t know the first thing about it…woops! How do you research how old your telescope is, where it was made, and what it was used for?
Well, I’m sorry to say this, but in many cases, this will be next to impossible to find out. The problem is that a lot of companies manufactured telescopes for all manner of customers and markets. Sailors, soldiers, sportsmen, hunters, sightseers, the leisured country gentleman on his estate, ranchers, birdwatchers, stargazers…the list goes on, and on, and on. Because of this, many telescopes were made and sold anonymously. It’s not uncommon at all to buy an antique telescope with absolutely no markings on it whatsoever.
That said, some manufacturers did put their names on their products, and did it loud and proud, too! Names like ‘Dollond’, ‘Broadhurst, Clarkson & Co’, and dozens of other smaller manufacturers would’ve engraved their details proudly onto the barrels or more commonly, the draw tubes of their telescopes.
But even without a name or address to research, is it possible to date a telescope? That really depends. The challenge is that telescopes made from the 1700s to the 1900s really didn’t change that much. Draw tube numbers rose and fell and it wasn’t uncommon for the same basic designs to be used for years, and years, and years! However, there are some small details which can guide you on rough dating of your telescope.
The Size of your Telescope
The earlier a telescope is, the larger it tended to be. Those from the early 1800s and earlier tended to be exceptionally long, and with only one or two draw tubes. The quality of manufacturing available at the time limited the size and complexity of telescopes and how compact they could be made. As manufacturing techniques became more advanced and refined, smaller and more intricate telescopes with improved optics became possible.
Engravings and Inscriptions
One of the most reliable ways to research the history of a telescope is if it has an engraving or inscription on the draw-tubes. As mentioned earlier, telescopes were popular as gifts in maritime circles, to commemorate promotions, milestones, long service, or were given as rewards for great deeds done at sea. Such inscriptions often included the date, the recipient’s name, the name of the party presenting the telescope, and the reasons for the presentation. Depending on the amount of detail given, there might be enough information provided to research the backstory of the telescope, as well as give us a rough date as to the telescope’s era of manufacture.
The position of a manufacturer’s engraving is also one way to determine a telescope’s age. Up to the end of the 18th century, manufacturer’s engravings tended to be on the ‘right’ side of the telescope, and after the start of the 19th century, manufacturer’s engravings tended to be on the ‘left’ side of the telescope.
“Uh, Brainiac – telescopes are ROUND. They don’t have sides”, I hear you say. And you’re correct – they don’t – but nevertheless, the positioning of an engraving on a manufacturer-marked telescope is one way of telling how old it is. From the 1790s and back, maker’s names and their details (addresses, etc) were engraved on the ‘right’ side, meaning that the first letter of the first word in each line of the engraving was closest to the eyepiece.
After the 1790s, for reasons unknown, telescopes tended to have their maker’s details engraved on the ‘left’ side, meaning that the last letter of the last word on each line of the engraving was closest to the eyepiece.
It’s a crude dating mechanism at best, but seems to hold up, in all the examples I’ve seen, both online and in antiques shops.
This excerpt was originally published in the February, 2017 edition of the TAT Antiques Magazine, and was reproduced here by the permission of its author…me! 🙂