Refurbishing a 6" F/5 Homemade Jaegers Refractor Telescope and Case

My astronomy club was recently donated a big pile of old astronomy gear, telescope parts and amateur telescope making equipment from the 1950s-1970s. One of the items of this "astro-hoard" was a 6" f/5 refractor telescope, with an objective, tube and focuser made by Jaegers. They were a premier shop for optical craftsmanship back in the day, and the lenses and focuser in this telescope were quite nice; however, the person who assembled it did what I would politely call a "hack job". When I picked up the items, this was just laying in a pile, and could have been destined for the scrap heap! In this Instructable, I will share how I took this crusty old telescope and fixed it up to a state fitting of its quality mostly using stuff I already had, along with refurbishing a wooden case to store it properly.

I used a variety of hand tools, including:

• Drill
• Random orbit sander
• Screwdrivers
• Hammer
• Sandpaper
• 3M scotch brite pads
• Disc sander
• File
• Tin snips
• Prybars
• Chisels and scraper

For consumables and supplies, I used:

• Self-etching primer
• Gloss enamel spray paint
• Spar Urethane
• JB Kwik Weld
• Open cell foam
• Contact cement
• An old yoga mat
• A Vixen style dovetail rail from Agena Astro
• Rubber feet
• Screws
• A utility handle
• A chest handle
• Braided steel cable and ferrules

I also used TinkerCAD and a 3D printer to create and print some adapter pieces for the diagonal and eyepiece

I chose to refinish a case and the telescope itself at the same time. I find with projects like this that require waiting to spray paint and waiting for finishes to dry, I'm much more efficient if I take on multiple things at once.

The case itself was from a completely different telescope from the same era, a Tasco 10 ET. Neither the telescope itself (which another member took to play with as a solar projection scope) nor the case were anything special. Honestly, the only reason I chose to refinish it was because it fit my planned scope and dew shield almost perfectly, and it was in decent enough repair that a bit of elbow grease was sufficient to get it in really good condition to store this telescope properly. As mentioned, the scope itself was just laying in a pile with other random tubes and bits and bobs, with no eyepieces or a mount or anything, so having a case for it will make it much easier to store and transport. Having a free one is a bonus!

I first removed all the hardware and put it in a container so I didn't lose any of the tiny screws for the hinges or hasps. Then, I removed all the other crap inside of the box - there were a lot of glued in and and lightly nailed pieces of wood to hold the old telescope and accessories in place, all of which would be in the way for my new telescope. So I took a hammer, scraper, chisels and trim prybar and gently removed all of them. I had to saw one of them in half to get it out safely, I was mostly concerned with tearing holes in the thin laminate on the top and bottom of the case. It's really cheap wood - almost reminded me of balsa wood - so working with delicacy and intention was necessary to keep it intact enough to use.

After removing all the internal pieces, I glued one strip of laminate that was starting to come detached and then sanded the surface. There was some sort of laquer on the surface of the exterior, and a bunch of scratches. I sanded with 150 grit, which is a finer grain than I normally would use but I was worried about sanding through the first layer of the thin laminate and wanted to go easy. It took maybe an hour to sand, but I got to be outside on a snowy March day so it was worth it. I finished with 220 grit to soften the surface a bit.

After sanding, I sprayed the outside with Spar Urethane. I've not really used this type of finish before, but was thinking it might be set in wet grass and otherwise be outside, so I chose to give it a try. This is meant for outdoor furniture and signs and such, and to be totally honest I used it because it was easy to spray vs brush on and I just had a full can of this lying around with no other options on hand for wood finishing!

After spraying three coats (the whole can), I let the finish dry for a day before reassembling to allow the finish to cure properly.

After letting everything dry, I reattached the hinges, handles and locking hasps. The side handles were awkward to use to carry up and down my stairs and through doors with the weight of the telescope, so I purchased another one and attached it to the front. Additionally, it came with two straps to keep the lid from opening too widely that I removed - they were just some fabric with upholstery pins tacking them in place.

I happened to have two braided steel cables with ferrules from another project that were the perfect length for this! So nice when that happens. I crushed the ferrules in my vise and found some screws in my random drawers full of them that made this feature much nicer. Additionally, I added some rubber feet to the back so that it won't get all scratched up in the future. The bottom wood is really thin, so I did not add feet there.

After reassembling, I added some open cell eggshell foam that I just had lying around, which was the perfect size to trim slightly and place in the top and sides. I tried adding to the bottom but it was too thick and the upper supports on the case prevented it from shutting. I thought about purchasing some thinner foam, but just happened to have a chunk of old yoga mat that was worn out - when folded over, it's the perfect thickness to protect the telescope and allow the case to close.

I'm pretty pleased with how it turned out. For how little work it was to refinish this case, it looks pretty good. The only thing better would be if it were made of hardwood instead of whatever soft wood it's made out of, but I can't complain too much for how little effort and the $0 I spent to refinish it.

This telescope was so poorly assembled that it took all of 10 min to take apart and get ready for refinishing. The lens cell was held in by a large hose clamp, so I removed that and pushed the lens cell out for safe storage. The focuser was press fit into the back of the tube, so it popped right off. I removed the balancing weight system, which I didn't reinstall because it's not necessary with the way that I will be mounting - using a longer dovetail rail on the bottom will let me slide the scope back and forward to get the proper balance point, rather than mess around with the weights.

The vinyl cover on the outside peeled right off, with no adhesive residue - a huge bonus! The baffles (rings) on the inside were falling out - they had been glued and screwed in place, but all of the screws fell out and the glue had failed. I took the one out that was just sliding around, and the other two left in place as much as possible.

After disassembly it became apparent that this would be a relatively straightforward refurbishment - refractors are just a lens, tube and focuser and all of those things were in good enough condition to keep using in the final product.

I spent more time than I probably should have getting the tube ready for painting. I took a long time to sand and scrub the outside of the tube to make any scratches pretty uniform, and remove a small amount of adhesive on the very ends of the tube. Scotch brite pads were great here, given the curved surface of the tube. I had a slightly more abrasive version than the typical green ones that worked phenomenally. Always wear gloves when sanding metal, aluminum especially gets all over your hands.

After sanding and scrubbing, I mixed up some JB Kwik Weld to fill some of the holes that I no longer needed from the weights and the old finder scope mount. JB Weld is great for stuff like this - you mix it up, fill the holes and then after it cures you can sand it down flush with the surface. I put tape on the inside of the holes to keep it from oozing into the interior, this worked really well.

Another thing I did was find some small screws for the baffles and countersink the holes for the heads a bit better. There were already holes for 3 screws per baffle around the outside of the tube, someone either didn't install screws or they fell out at some point, so this will help keep them in place in the final assembly. I just took a larger drill bit and worked the holes til the screws would sit flush.

The largest flaw in the tube was one of the most critical pieces. Where the lens cell mounts was cut with a hacksaw, pretty crudely. This means that it is hard to get the lens cell to sit flush in the tube and thus parallel with the focuser - in telescopes, this is called collimation, which really means optical system alignment. If the lens is at an angle to the eyepiece, things will be out of focus or the telescope will not perform well generally. To fix this issue, I ground it down on my Shopsmith disc sander. To mark a line on a tube like this and ensure it is going to be a flush edge that is perpendicular to the side of the tube, all you need is a piece of paper. Wrap the paper around the tube and tape it in place so that the overlapping parts are lined up. This gives you a straight line as a reference, which I kept taped on there during grinding to ensure I was taking off material in the right places.

I also set up a fence perpendicular to the disc to help as a reference point for spinning the tube when grinding. It was just a scrap piece of wood and some clamps, it helped to prevent me from approaching the sander at a weird angle.

After sanding with the disc sander until the distance from the paper was the same all the way around, I cleaned up the edge with a file and moved on to painting!

With all of the sanding and scrubbing I did on the tube, it was a good smooth surface ready to take paint. I wiped it down with acetone to remove any fingerprints or grease. I've had good luck painting aluminum and galvanized steel with self-etching primer. This etches the surface really well, and helps paint stick to surfaces that might be difficult for it to attach to. I highly recommend for these applications, your paint has a much better chance at succeeding in adhesion. I gave this three light coats.

After letting the primer dry for a day, I moved on to painting the tube Dark Hunter Green. It was hard to choose the color( I spent like 10 min in the Ace paint aisle), I almost went with a sparkly blue paint but felt like this would be a good color to pop with the light blue dovetail rail. I painted four light coats of the green paint on the tube and gave it a couple of days to dry properly. I also shot some flat black paint on the inside and on the back of the focuser to cover the failing flocking. TBH, I'm not terribly happy with the paint I used - the color is good, but the can spray nozzle must have been wonky because it left a more textured finish than it should have. I don't hate it enough to repaint, but that's the one disappointment from this whole project.

While the paint was drying, I focused on the mirror diagonal and eyepiece modifications. This telescope came with an adapter to add 1-1/4" eyepieces to the focuser. It's a real nice adapter that I will keep, but I also got a sweet military surplus periscope optics setup with this whole pile of old astronomy stuff. It has a decent mirror for the diagonal, and a really nice eyepiece with a wide field that I had read Jaegers used in some of their eyepieces. Some internet sleuthing revealed that it is a 32mm Erfle style eypiece, which was designed for a periscope in a M16C tank periscope. This gives a magnification of just under 25x and a really wide field of view, so it is a very good option for this scope. I would wager the original owner intended to couple these two items together and never got around to it.

So, I decided to try modifying these to fit the focuser on the telescope, which has an unusual diameter that is not standard for regular eyepieces. Additionally, the tank periscope and eyepiece are heavy which helps balance out the telescope with how short it is and how heavy the lens cell is.

To do that I just measured and 3D printed a ring to fit around the tube of the diagonal, and a separate one to fit normal 2" eyepieces into the diagonal. These both took all of 5 minutes to whip up in TinkerCAD. I made the ring a bit too big so had to sand it down slightly, but wanted to make sure it fit pretty snugly anyways. I may keep this or swap out for a regular 2" diagonal, but it was too sweet of a find to pass up! Given the wide field of this scope, it's not a deal breaker to have a single eyepiece semi-permanently attached. A lens of this type is very similar to a huge binocular, and in fact the "astro-hoard" even had two more of these objectives to create just that!

I wanted to reattach the lens cell last so that it would be easy to work with the telescope tube (called the optical tube assembly or OTA in the amateur astronomy community). First, I attached a vixen style dovetail rail that I purchased for this project. It was the only major expenditure on this whole thing. I reused the holes that had been drilled into the tube for the previous mount, and just scrounged some large fender washers and some stainless 6mm bolts and nylok nuts. After attaching I spritzed with some of the flat black enamel - you don't want shiny hardware inside of the tube as it bounces light around. This helped a lot to keep the tube from rolling around as I worked on it with the other items. I also attached a utility handle at roughly the balance point by drilling and tapping the tube for 5mm bolts.

For the focuser, I took a tailor's tape and temporarily taped it to the tube. It's easy to evenly and accurately space fasteners at 120 degrees around a tube like this if you just divide the circumference by 3 and space them accordingly.

I drilled through the tube and into the focuser, tapped for 3mm and used some short stainless 3mm bolts and washers. To keep from drilling too deep, I just put a piece of tape on the drill bit as an indicator stop. I can't believe that the previous owner just pushed this into the tube! With how heavy the focuser is, it was destined to fall out if I had not attached properly.

The way that this lens attaches to the tube was good enough to keep using - there's no real way to safely drill into the lens cell metal to attach it like the focuser. I cleaned the inside of the lens with 91% isopropyl alcohol and some cotton swabs, and did the same to the outside. I used a lens duster that I typically use for eyepieces to get grit off beforehand so that the lens didn't get scratched.

I put the lens on a cardboard box to keep any junk on the floor from scratching it during this process, then pressed the whole assembly onto it - it went right on! I used wide gorilla tape to cover the holes and splits at the end of the tube that the previous owner had cut to allow for it to expand over the lens cell. The hose clamp was too long, so I trimmed it down and filed the edge to keep it from cutting anyone. The dew shield just press fits on the end, and I left it that way rather than permanently attaching.

I'm excited for a few clear nights to get this thing out for viewing! I attached it to a mount that I have for my solar telescope and binoculars - it is definitely a bit heavy for it so I will pair with a different mount that our astronomy club already has. I need to attach a finder and hope to use the Cricut I can access at work to print some labels for it in the style of the original company's logo.

In looking through it during the daytime, I can tell it's a very nice telescope with a wide field and clear image. It will be great for viewing the moon and other things like the Andromeda Galaxy, Orion Nebula and Pleiades. I hope this Instructable inspired you to refurbish an old telescope and use it to view the night sky!