A Review of a Vintage Monolux Refractor Telescope

The telescope in received condition

After joining an enjoyable astronomy egroup that was devoted to the use of small, refractor telescopes, I was enthralled with the group, but I didn't have a telescope that fit their mainstream emphasis. I was thrilled when a member graciously donated an abandoned, vintage 60mm Monolux of 700mm focal length (f/11.7) to my cause.

As you can see, the old Japanese made instrument had seen a number of years and showed some wear. But the Monolux is considered a good representative of the many Japanese telescope sold in the heyday of small refractor telescopes. Based on that I wanted to give it a fair tryout.

Visible in this image are a few scrapes and scratches, and a couple of holes that were likely used at one time to mount a finder scope. You might also notice that the focuser is of the 0.965 inch variety. It still worked well, but had only about a 2.5 inch travel, and of course only accepted the small 0.965 inch eyepieces.

Here's another view of the telescope as received. Incidentally, the tripod was not part of the donation, only the telescope. Again, you can see a few unused holes in the body of the telescope.

Here you get a better view of the focuser assembly. The holes in the side of the tube were likely used to mount the telescope to its original mount. The telescope's original mount was long gone, but that's not likely a great loss. Refractor telescopes even in the era of this model were still notorious for having mounts that were undersized.

The Adventure Begins

The first thing I had to do was rig up a mounting for the telescope. Fortunately that problem was already mostly solved. I just had to drill a 1/4 inch hole in a 3 inch hose clamp, and use the clamp to fasten the Monolux to my pipe fitting tripod. A 1/4 inch screw of 2 inch length goes through the hose clamp and through the mounting board fastened to the pipe fitting tripod.

My first light experience was a bit disappointing. When I looked at Saturn, I was unable to focus to a nice, crisp image. I could see that it was the planet Saturn for sure, but the image was definitely sub-par. I pointed the telescope over to a moderately bright star to check out the in and out of focus star images.

On one side of focus the star image looked normal, but on the other side of focus the pattern was terribly distorted. Something was clearly wrong. Was the telescope a dud?

At the suggestion of a member of the aforementioned astronomy egroup, I examined the telescope's objective. It is an air-spaced doublet. After trying all combinations of arrangement of the two elements, I determined that as received, the front element had in the past been removed and accidentally reversed when replaced.

After correcting that discovered anomaly, I tried for another chance at a first impression. Images were much better. At low to moderate power the star images looked fine. But at higher power in the 100x range, images were still not quite as good as I'd hoped. Another glimpse at a star image revealed a noticeable amount of astigmatism.

Astigmatism is characterized by oval shaped out of focus star images, with the inside-of-focus oval at 90 degrees to the outside-of-focus oval. By rotating the eyepiece and seeing the pattern stayed in the same configuration, I was able to confirm that the astigmatism was coming from the telescope's objective, not the eyepiece.

On another tip from an egroup member I spent a day meticulously rotating the objective elements with respect to one another. After each adjustment, I would re-test the arrangement by looking at a pseudo star image. My pseudo star image was the sun's reflection off of a power transform insulator some 1/4 of a mile away. The curved surface of the insulator gave a reflection that proved a worthy fake star. I was amazed that this technique worked, and by following the procedure through I was able to find an arrangement of the objective elements that removed the astigmatism.

Eureka!

More actual astronomical target observations through the telescope confirmed that it was performing well. Planetary images were crisp and tolerated magnifications of up to 150x. Moon images were very pleasing. The telescope was also able to split some tight double stars near it's theoretical limit.

It was time to move forward.

The Decision To Refurbish

Next I sanded and repainted the telescope's outside. Showing no imagination at all, I painted it white. After about 3 coats of paint, the telescope tube looked good as new.

I then re-installed the objective cell, and added a 6x30 finder scope. I decided to not re-install the original focuser. Instead, I purchased a quality 60mm focuser from Meridian Telescopes. The focuser is a heavy duty focuser of metal construction with a 6 inch travel, and accepts standard 1.25 inch diameter eyepieces. When I finished installing the focuser, I stepped back and admired a fully restored, vintage 60mm Japanese refractor.

At left you see a closeup of the refurbished telescope. No more scratches and unused holes. You can see the new focuser in this image, and the new finder scope. The telescope is shown mounted on my good old pipe fitting tripod. The pipe fitting tripod is easy to use, and makes a super steady mount for my new old telescope.

The mount, as shown on the pipe fitting tripod page serves multiple duty. A single wing-nutted bolt is all that must be removed to switch to either my 50mm Jaegers refractor, or my newly completed 60mm f/16.7 Carton refractor. By switching tripod heads, I can also use the tripod to hold my ETX90 when I'm in a Maksutov mood.

The Views

I've had a chance to do a little viewing through the 60mm Monolux since the final optics alignment and the refurbishment. Starting with the moon, I've been startled by the clarity. I can routinely use magnifications up between 100x and 150x. Comparing it to a formerly owned Meade 90mm refractor (a Chinese import), I'd have to say that the image quality in the Monolux is better and the images crisper.

I've looked at Jupiter on a number of occasions. I could easily see the two major belts on Jupiter, and see that the Southern belt is split into two narrower belts. I could make out darker splotches along the Northern belt. I was not able to resolve the Great Red Spot this time around, and I understand that it's been a rather low contrast object. I was, however, able to spot Io's shadow as it shuffled across the planet. The shadow was very tiny, and not always visible, but I could make it out most of the time.

I haven't looked at many DSO targets yet. I've seen the Andromeda galaxy (M31) and one of its companions (M32), the Ring Nebula (M57), the Pleiades (M45), and the double cluster in Perseus. I was able to just glimpse the Crab Nebula (M1) from my backyard observing site. This is just a tiny fraction of the objects within the grasp of this size telescope, and I list these few as just examples of what such a small telescope can do.

The Monolux does a very nice job on double stars. Star images are always crisp, and at moderate power at most a single, dim ring is seen around the brighter stars. Contrast that with my ETX90, which while having excellent optics, always gives couple of shimmering rings around even moderately bright stars. The central obstruction of the ETX90 Maksutov optics causes the brighter diffraction rings. While the ETX90, with its greater aperture, can split closer doubles, the view is not as pleasing as through the Monolux refractor.

With its light weight and low-maintenance, solid construction, the Monolux is a great telescope for those impromptu or short evening tours of the universe.

Summary and Final Thoughts

The reputation of the poor 60mm refractor has taken a beating during the last several years. Such telescopes used to be considered not only fine beginner telescopes, but good supplements to any amateur astronomer's collection. Just look at what a 60mm Unitron goes for now-a-days, if you can find one for sale.

Now, most 60mm refractors are Chinese imports, made to inexpensive standards and sold by most distributers as telescopes for kids. They come with ultra-cheesy mounts and poor quality eyepieces. No wonder they don't inspire many youngsters to become astronomers.

But if you want a lot of fun and a bit of a challenge, find an abandoned vintage telescope at a garage sale or on eBay. There are a number of brands you'd be safe with. The following list is not exhaustive, and with a bit of research you can learn of other brands: Tasco (yes, the old ones were good), Towa, Sears, Monolux, Edmund, Unitron, and Jaegers.