Vintage Telescope Restoration - Towa 339


Rod Nabholz


On a recent vacation in Wisconsin, I was lounging around perusing listings on Craig's List when an ad for an 80mm f15 refractor and mount caught my eye, the lister referred to it as a "Katana".  The condition was described as "fair", and the images were small and unsatisfying, but the asking price was attractive and my curiosity was aroused.

As luck would have it, the owner lived in a town that was on our route home, and he would be available when we would be passing through, so I made arrangements to meet him and take a look. 

Upon my arrival, I left my patient wife and kids in the car while I followed the the owner into his garage.  He explained that he had bought the scope years ago at an estate sale in Wyoming, intending to restore it, but never got around to it.

He handed me the scope and I checked the label, and sure enough it was labled "Katana".  But more importantly down in the corner of the label was the "Circle T" mark of Towa, a well respected Japanese optical company.  This was a quality scope.

It was about there that the good news ended.  It was a mess.  A quick once over brought to light a number of problems.  The finder bracket was broken, one side of the focuser shaft and knob was missing, broken off just this side of the pinion.   The bubble level had given up its bubble.

 The finder lens was chipped in numerous places around its perimeter.  The whole scope and mount was dirty and showing signs of rust in many places.  The wood legs of the tripod were shedding their finish, with portions down to raw wood.

By now, I had great fears of what I would find when I looked at the objective. Swinging the tube around and peering into the dew shield, my eye was first drawn to a good size spiders web/nest, with the rest covered with a good deal of dirt. All of which could have been prevented by the lens cap that was stored in the eyepiece case....of course it was relatively clean - DOH!   A quick scan around the objective's edge showed one relatively small clamshell chip. That was certainly disappointing but the scope should still provide good images.

In the end, I decided that although this was going to be a challenge, it could be fun if I could buy it right.  I explained my concerns to the owner and made an offer that reflected the work ahead, and he accepted. 

As I carried it back to the car, my wife was giving me that "what now" look.  It was clear she did not have the "vision". I said "trust me"

Once we returned home, I took further stock of what I had. I did some research and discovered that the scope was a Towa Model 339, a 80mm F1200mm scope that was sold by many vendors under various names and model numbers.  I have not been able to determine what business entity marketed the scope with the name of "Katana" but it could have been anything from a local or regional department store to a national mail order house. Such was the state of  the telescope manufacturing business at the time, (like today) lots of marketers, served by a few manufacturers. This scope was probably built sometime in the 70's.

A few more shots of the condition it was found in.

It came with a re-purposed case of eyepieces and accessories.  In true "Home Built" style, the previous owner used elastic waist bands from underwear to fashion retaining straps for some of the components - Gotta Love That!

Contained within was a nice assortment, 5 eyepieces, a diagonal, barlow, porroprism, moon and sun filters and the drive wheel for an optional motor drive.  All a bit dirty, but servicable.

My work was cut out for me.

The Hose Down

Well, I did not actually use a hose, but I was tempted.  Time to get the dirt and grunge off and see what was underneath.

I was very curious as to the actual condition of the objective, for obvious reasons.  I was really hoping that what I was seeing was surface dirt, and the there were no surprises like scratches or fungus underneath.

I started with the spider web.  Using a Q-Tip, I simply twisted it in the web and after a couple tries, it all came out. along with the culprit, long since gone on to the spider afterlife.

Whenever possible, I try not to touch refractor lens elements, and was planning for that to be the case here if possible. I was also really hoping that I could get it clean without removing it from the cell.  That is always a perilous endeavor, and the single best way to add another perimeter chip or two.

To clean the objective I used a triggered spray bottle filled with distilled water.  Working one side at a time, I sprayed the lens and repeated until a good deal of the surface dirt had rinsed away.  I then switched to distilled water with some Dawn dish soap. I repeated the same process of spraying using the soapy water.  I could see that the detergent was removing some of the remaining stubborn dirt.  Back to distilled water for a final rinse.  After doing the same on the reverse side, I could see that almost all of the dirt was on outside surfaces, with just a few harmless specs that appeared to be inside. Fortunately no disassembly of the cell would be necessary.

Cleaned and rinsed, I was very pleased with the results - all without touching the glass!

Next came a bath time for the mount.  Dish soap, water and a brush to get the grime off.  The tripod hub was the worst!  Hard to imagine how it was stored to get this dirty!


With the bath finished, the mount was clean, but not at all pretty yet.  Much more work to do.

Finding The Way

As I mentioned earlier, the finder mount was broken and needed to be addressed.   I scouted around on Ebay to see if luck would be with me and I might find an original to replace it, but none were located.  I did however come across something that looked close.  Telescope Warehouse was offering a new Meade 6x30 finder with a "tall" bracket for $17.  It looked very much like the broken bracket, and so I took a chance and ordered it.

When it arrived, it seemed to be a match.  The holes on the base of the mount were spaced the same as the original.  I tried slipping in the original finderscope, and it fit perfectly.  Hey, this just might work!  I took it over to the scope to see about mounting it, and it was then that my hopes for an easy fix fell apart.  The base of the original finder had a pronounced radius, and the replacement much less. It was not a fit.  If this was going to work, it would mean modifying the base.

So I did.  Using the original base as the template, I traced the curve on some yellow electrical tape and used a hobby knife to cut it out.  Using that as a template, I transferred the shape to the new bracket and colored the part I needed to remove.

Then, using my Redneck Milling Machine (Dremel Tool) with a sanding cylinder mounted, removed the unneeded metal until I had a fit.

Time to Focus

Next up was addressing the broken focuser shaft, and again Ebay came to the rescue.  I found an entire focuser unit from a Celestron Astromaster 70mm that looked like it might be a good size match, was affordable, and I thought looked "appropriate" for my scope.

I removed the shaft and installed it in Katana. It was a great fit and worked perfectly, looks pretty good too.

Bubble Level

I can't really explain my attraction to this little feature of the mount, but the bubble level is one of my favorite parts of this scope.  Maybe because it sort of defines a time when these scopes were built to a slightly higher level of quality.  The bubble level was comprised of the level vial that was mounted in what appeared to be an aluminum casing, that was then filled with plaster of paris to secure it.  It was all mounted on the scope by three screws that were drilled and tapped unto the leg hub of the mount.  All of those parts, assembled in the manner they are and, requiring machining to mount, would certainly be among the first of the cuts made by a modern manufacturer looking to reduce costs. That, for me, makes it a symbol of the the times when such things were considered important and valued.  I was determined to restore it to operation as a tribute.

First step is to liberate it from the holder - started by chipping the plaster, but decided there was a better way.

I filled the holder with water and let it go to work on the plaster, and it was indeed much easier.

When I had removed enough plaster to remove the actual bubble vial, I found that the vial had split, with the top coming free, allowing all of the liquid to leak out - Well there's your problem....

I needed a replacement vial, so off to the Obscure Telescope Parts Store again (Ebay),  I was able to find a 13mm bubble vial and ordered some.  By the way - 12mm doesn't work, don't ask me how I know, let's just say I will make you a heck of a deal on a couple...

The next challenge on this task was finding a way to buy less than 5 lbs of plaster of paris when all I needed was a thimble full.  As it turned out, I stumbled across this little kit at the local Walmart.

Still about 300 times more than I needed, but cheap.

After stripping the holder of its paint and applying a fresh coat of gloss black paint, it was ready to receive the new vial

I mixed some of the plaster up, placed the vial in the holder and filled the back side with the plaster.

It ended up being overfull, so I removed the extra using a damp cloth, moving the vial back and forth, eroding the extra plaster until it was flush.

Then, using the extra vials as a reference, checked to see that it was properly callibrated - it is well within tolerance and ready to take its place on the mount.

Eyepiece Tray and Light

Another cool feature of these older Towa scopes is the lighted eyepiece tray.  Not sure that it is all that useful, and unless you secure a red bulb for the lamp, will not help with your night vision and make enemies of your fellow astronomers, but dang, It is hard not to like it anyway. 

Miraculously, a minor repair to a lose wire was all that was need to return it to operating condition. Many of these suffer from damage caused by leakage from long exhausted batteries.  With the Electric's sorted, the tray and light needed a cleaning, some body work and a new coat of paint.

These trays can get bent pretty badly by owners who can't be bothered to remove them when moving the scope around, and mine had suffered some.  I straightened it as best I could and then cleaned and smoothed the paint chips in preparation for a paint job.  I did the same prep for light's battery box.  After a couple of coats of paint, it is looking good.

I took the opportunity to clean, polish the parts and repair the connections of the lamp and arm assembly before reassembling.

Then, I just reassembled all of the pieces. It made for quite an improvement, from this "Before" shot:

To this:

I was subsequently able to find a red bulb - it is even cooler now... ;^)


I welcome your comments and questions at

 2014   Rod Nabholz

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