A Review of a Vintage Monolux Refractor Telescope
After joining an enjoyable astronomy egroup that was devoted to the use of
small, refractor telescopes, I was quickly enthralled with the group. It
brought back memories of my childhood, during which I often thought of buying a
60mm refractor, but never did because conventional wisdom was that 60mm wasn't
big enough. But the views through 60mm telescopes, described by many of the most
experienced members, really caught my attention. Was what they described
The problem was, I didn't have a telescope that fit their mainstream
emphasis. My only refractor was a 50mm Jaegers
Refractor, and I was admittedly amazed at how well it presented those
targets. But I was a bit dubious about what besides the moon and planets one
could see with a small refractor. Yet you can even buy a 60mm refractor
telescope on a computerized mount, like the Celestron
60LCM Computerized Telescope (Black). But is there much to see with a 60mm?
I'd never used my little 50mm telescope for star objects, and wasn't sure it
would show much. I frankly didn't think a 60mm would show much either.
But the talk in the egroup enticed me, and I wanted to share in the
experience. To do that I figured I needed to find myself a good 60mm telescope.
I went for the used telescope route. I was thrilled when an egroup member
graciously donated an abandoned, vintage 60mm Monolux of 700mm focal length
(f/11.7) to my cause, so that I could use precisely the size instrument that
was causing all the buzz in the egroup.
The telescope in received condition
As you can see in the image above, the old Japanese made instrument had seen
a number of years and showed some wear. It definitely needed some tender loving
care. 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
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 where a tripod cradle used to fit.
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 -- with the exception of a few, like
the venerable Unitron.
The Adventure Begins
I found I was on a bit of a journey when I decided to refurbish the vintage
Monolux. I cover a few of details of my efforts on this web page. I imagine
that some of the problems I encountered are likely typical of those you might
experience should you decide to refurbish a vintage refractor telescope.
First, when I got the telescope, I had but one 0.965 inch eyepiece to use in
the instrument. So I purchased a hybrid diagonal that allowed me to use my 1.25
inch eyepieces. The hybrid diagonal has a 0.965 inch snout on the telescope end
so that it will slide into a 0.965 focuser. On the eyepiece end it has a full
1.25 inch adapter.
This provided a workable solution for using most of my 1.25 inch eyepieces,
but there were a couple of limitations. Since the focuser didn't have a locking
screw to hold the eyepiece or diagonal, the heavier 1.25 inch eyepieces would
cause the star diagonal to rotate under their weight. I had to be sure the
eyepieces were placed in a perfectly up position. Second, the limited
2.5 inch travel of the focuser didn't let me get full use of my Barlow. I could use it on
some eyepieces, but not others.
To use the telescope, the first thing I had to do was rig up a tripod or
mount of some kind. Fortunately, as shown above, that problem was already
mostly solved. I had already made a tripod (actually a pedestal mount) for my
little 50mm refractor. 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
plywood cradle fastened to the pipe fitting tripod. This simple method provides
a telescope mount of exceptional stability and ease of use.
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. Viewing star images at high power is a common way to test
telescope optics. A description of what you can determine about your telescope
is described at the Starizona Star
On one side of focus the star image looked reasonable normal (a bit oval),
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 with the two
objective elements separated by a spacer ring. 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
After correcting that 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 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
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 finding that 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. Had the eyepiece been the trouble, the
orientation of the oval patterns would have rotated as I rotated the
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 out of focus images by looking at a pseudo star image. My pseudo
star image was the sun's reflection off of a power transformer insulator some
1/4 of a mile away. The curved surface of the insulator gave a solar reflection
that proved a worthy fake star. I was amazed that this technique worked, and by
following the procedure carefully I was able to find an arrangement of the
objective elements that virtually removed the astigmatism.
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, which is about typical for a good 60mm telescope.
Moon images were very pleasing. The telescope was also able to split some tight
double stars near it's theoretical limit.
The 120x maximum that you often read for the maximum magnification for a
60mm is obtained by applying the general rule of maximum useful magnification
as 50 times the objective diameter in inches. Thus, 2.4 x 50 = 120. However,
atmospheric turbulence is one of the contributors to this general rule, and
small aperture refractors are less affected by atmospheric turbulence than
larger instruments. It's not uncommon for quality 2.4 inch (60 mm) refractors
to achieve up to 75 times per inch of objective diameter. For a 2.4 inch, that
means up to 180x when seeing is exceptional.
With a correctly installed objective with its elements in an optimal
relationship, it was time to move forward.
Schrodingers Cat Small Poster
The Decision To Refurbish
Now that I knew the Monolux had good optics, I decided to go the distance
and refurbish the vintage refractor. To start, I went after all those old,
unused holes. I filled them with epoxy, and after the epoxy dried I sanded it
down to the point of being unnoticeable.
Next I removed the focuser and the objective cell and repainted the inside
of the telescope tube with flat black paint. The original black coating was a
bit thin in places, and with only 60mm of aperture to work with I didn't need
any interference from stray light sources.
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 added a 6x30 finder scope. I decided to not re-install the original
0.965 inch focuser. Instead, I purchased a quality 60mm focuser from Meridian
Telescopes (alas, they are no longer available). The focuser is a heavy duty
focuser of metal construction with a 6 inch travel, and accepts standard 1.25
inch diameter eyepieces. Since the position of the eyepiece with standard 1.25
inch star diagonal was further away from the objective than with the original
focuser, I had to shorten the main tube by the difference. When I finished
installing the focuser, I re-attached the objective cell, stepped back and
admired a fully refurbished, vintage 60mm Japanese refractor, now capable of
directly using the more standard 1.25 inch diameter eyepieces.
Above 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 to 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 my 50mm Jaegers refractor, my DIY 60mm f/16.7 Carton refractor, or my
Vixen 70mm refractor. By switching tripod heads, I can also use the tripod to
hold my ETX90 when I'm in a Maksutov mood.
Since this is a vintage telescope, it is all metal construction, and now
with an updated focuser for the larger 1.25 inch eyepieces. I could go one step
further with this instrument, and bring it up to the level of the previously
suggested computerized model. How? By buying something like the iOptron
SmartStar-E 8500G Computerized AltAz Telescope Mount (Terra Green). I could easily adapt this computerized mount to my
pipe tripod and really have a top notch system. Maybe one day I will.
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 90s era 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.
Jupiter 2010 with 60mm Refractor
Update. In 2010 the Southern Equatorial Belt on Jupiter seemed to
disappear, as revealed in the above photo obtained with my 60mm Carton Refractor. This strange
phenomenon of belt fading has occurred before, though not often. Because of
the missing SEB, I was able to detect the Great Red Spot for the first time
with my Monolux 60mm telescope. When the SEB is visible, it merges with the
Great Red Spot, making it to difficult a target with the Monolux. Note that
while this image wasn't taken with the Monolux, it was taken with my
Carton 60mm, a same size telescope.
I haven't looked at many DSO targets with the Monolux 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. The Orion nebula is a
wonderful target, and the 4 brightest stars of the Trapezium are visible
through this 60mm. 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 redistributes some
light to the first few diffraction rings. While the ETX90 with its greater
aperture can split closer doubles, the view is not as pleasing as through the
With its light weight low-maintenance, and solid construction, the Monolux
is a great telescope for those impromptu or short evening tours of the
universe. Since most of my observing sessions fall into that category, my
Monolux and Carton 60mm telescopes get quite a bit of duty.
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
with lots of plastic, and sold by most distributors 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, Carton, and Jaegers.
If you observe with a small telescope, or even a large telescope, I invite
you to the Amateur
Astronomer Survey page to contribute to the survey. See how your use of
telescopes and target interests line up with other observers.