3"-ish Refractor Shootout

by Joe Bergeron

The favorite activity of many amateur astronomers is evaluating and comparing various telescopes. Many pass multiple telescopes through their hands every year as they sample the astronomical smorgasbord, rarely keeping any long enough to truly get to know it, let alone to do any systematic observing with it. Perhaps a better title for these people is amateur telescope evaluators.

Why should I miss out on the fun? I find myself in possession of three refractors in the three-ish inch class, and there's no reason I shouldn't set them up all at once and spend an evening eyeballing the same objects with each one to assess their strengths and weaknesses in a completely arbitrary and subjective manner.

The three contenders are as follows:

Left to right: Stowaway, Eikow, and Jaegers refractors.

Your collective gasps echo across the countryside as you read these words. "What," you ask, "is it not unfair to compare an apochromat of significantly greater aperture with those poor achromats?"

Well, yes, I agree with you, it is unfair. However, there are those who might not agree. The world boasts a few peculiar characters who carry on an ardent love affair with achromatic refractors. They enjoy a sort of refractor nostalgia that borders on the religious, sometimes claiming that not only are their achromats optically superior to apochromats, and more desirable, but somehow more spiritually pure as well. These romantic souls love to cast their thoughts back to the long-gone years when it was possible to make significant astronomical discoveries by looking at things through refractors. These refractors were almost invariably achromats, because apochromats did not exist in any great numbers until well into the 20th Century. Actually, the most fundamental, revolutionary discoveries were made with even earlier single element refractors, but despite this proud history there has been (so far) no modern attempt to promote them as superior.

Stowaway mounted on Orion SkyView Pro mount with Rigel QuikFinder on tube.

So, let us agree that in the minds of at least a few of my readers, the fancy-schmancy short focus apochromat might actually be at a disadvantage, despite its greater aperture.

A few words about each of the telescopes involved. The Jaegers dates from the late 1970s and has been a humble and lovable companion on many occasions since. However, its objective lens is not exemplary, showing enough astigmatism to impact its performance at high powers.

The lovely Eikow is a Japanese import dating from about 1960. It's a "rescue telescope" bestowed upon me by generous amateur astronomer Jon Isaacs, and I have cleaned it up and restored it to the best of my ability. This scope offers a window into the state of amateur astronomy as it was fifty years ago. The German mount is a finely made little thing, with decent setting circles and manual slow motion controls on both axes, a refinement you don't find on many American-made mounts from the same period. It is, however, too small for a telescope of this size. It's a bit wobbly, and touching the slow motion control cables imparts a considerable low-frequency vibration to the image. It would be better suited to a 60mm scope. For actual use, my Skyview Pro mount is far superior for this telescope. I could even mount it on my Celestron AVX mount and experience the wonders of goto with a very small instrument.

The telescope itself leaves little to be desired. The objective is as perfect as any I've ever seen. The focuser is impressive. The drawtubes are so wide they could work well with most 2" eyepieces. An 1.25" adapter from Vixen screws directly onto the focuser, allowing me to use modern eyepieces without any compromise. Finally, it comes with an imposing 40mm finder which is sharp and a pleasure to use.

This telescope shows that the Japanese refractors of the 60s could be nice indeed, even if they weren't labeled "Unitron". This particular model is the same as some that were offered by Swift. Some people believe that these Swift/Eikow objectives were made by Takahashi, and that they are more consistently excellent than Unitron lenses.

For more on the Stowaway, refer to its separate article elsewhere on my site.

The May evening I chose for this exercise was sweet, warm, and moonless, with very good seeing and a friendly chorus of companionable frogs. A few fireflies twinkled among the trees. My first target was Venus, at that time a lovely, narrow crescent on its way toward a rare transit of the sun. Using all three telescopes at a medium power of about 75x, the results were as I would have expected. The views were identical, except for the gradations of chromatic aberration. The Jaegers showed a garish aura of purple and magenta, the Eikow showed a moderate violet glow, and the  Stowaway showed a brighter image free of any color error.

Saturn turned out to be the best object for differentiating between the telescopes. At 140x the Jaegers wasn't very sharp. The view wasn't offensively bad, but it showed little detail. The Cassini division was glimpsed only fleetingly, and the disk was bland.

Conveniently, the Eikow has twice the focal length as the Jaegers, so I could match their powers by using eyepieces of twice the focal length. The Eikow was much better on Saturn, giving a sharp image at 140x with the Cassini division cleanly presented and a broad belt visible on the disk. Only a hint of color error was seen on this dimly-lit planet. It was a fine view that anyone would enjoy. At 200x the image was rather faint and a bit soft.

The Stowaway was again in a different league of performance. At 172x and 189x its image was even more perfectly defined than the Eikow was at 140x, and of course bigger, more highly resolved, and much brighter. I was better able to separate that belt from the polar hood. The Cassini division was perfectly etched. The view was exquisite, and I spent a fair bit of time staring at it, almost forgetting about my comparisons.

After that I didn't bother to include the Jaegers in the high-power comparisons, because it just couldn't compete.

3" f/13 Eikow refractor, circa 1960.

My next target was Porrima, Gamma Virginis, a famous binary that is again becoming an easy object after a few years of being so close it was very difficult to split. At 140X the Eikow offered a very clean, perfect split with the two stars nearly touching. The Stowaway was just as well defined at 172x, but of course brighter. For aesthetics I would call this comparison a draw.

Next came Izar, Epsilon Bo÷tis, called Pulcherrima by its discoverer F.G.W. Struve, one of those sainted visual astronomers of the 19th Century. The Eikow gave a perfectly lovely view of this delicate unequal pair, but the view through the Stowaway was like an illustration, with two perfectly round, hard dots of light, well separated.

Permit me a digression about the nature of telescopes and testing. Amateur astronomers rightfully brag about their instruments when they display stars as neat, round Airy disks surrounded by clean diffraction rings. What is rarely mentioned is that this display has everything to do with the telescope and the nature of light and nothing to do with the stars we are supposedly observing. Those disks are not the true disks of the stars, but artifacts caused by the small size of our telescopes and the wave nature of light. They are good physics demonstrations, but poor representations of the stars and their true appearance. When we see a double star barely separated, we are failing to see the vast gulf of space that in fact separates the two distant suns, which should still be minute points at the magnifications we use, if not for the limitations of our telescopes.

At 75x there was nothing to choose between the two three-inch refractors on M13...the views were identical. The Eikow did a bit better at high power than the Jaegers, probably because it's sharper. Neither did more than suggest any resolution, but then this was not an exceptionally dark night, even for this location. The Stowaway was of course better than either, showing more distinct resolution, but the difference was not spectacular. The Ring Nebula gave comparable results.

3" f/6.5 Jaegers refractor on Desert Sky Astro mount.

And so, the hierarchy turned out to be about what I expected. I find that the Stowaway is the superior deep-sky telescope and greatly superior as a planetary telescope.

But I am not immune to the allure of telescope nostalgia. With the Eikow I like to imagine what things were like when such telescopes were new. A family buying such a luxurious instrument at the dawn of the Space Age had a thrilling adventure in store. That was the very tail end of the era where big discoveries could be made visually, before space probes, orbiting telescopes, CCD cameras, and so many other refinements of today existed.

Atmospheric seeing limited the potential of professional telescopes, so their resolution advantage was rarely fully attained. Planetary photography was so poor that anyone with a good amateur telescope could see more than could be photographed with the world's largest telescopes.

Very little was known about the physical conditions of the planets, and much of that feeble knowledge was visually-derived guesswork. Astronomy books seriously discussed the dark lichen patches of Mars and speculated about the primordial jungles than might exist beneath the clouds of Venus. Even as NASA planned to go to the moon, some astronomers feared their spacecraft could sink into seas of smothering lunar dust.

Therefore anyone with a nice telescope like the 3" Eikow was on a nearly equal footing with the best planetary astronomers in the world. Someone with a good 3" refractor could gaze at the moon and planets, see a good fraction of what the professionals could see, and dream about what might exist out there, unhampered by any actual knowledge of the bleak conditions on our neighboring worlds, which are so desolate, and such poor containers for the hopes and aspirations of the human race, and so useless in the event that we ruin this astonishing planet we inhabit. It was in some ways a more hopeful, innocent time. Achromatic refractors, vintage or otherwise, can be kindly, gentle reminders of those times.