Small Scope Saga

Jack Kramer

There's an adage in amateur astronomy that the smaller the telescope, the more often it'll be used. It's great to have the convenience of a compact telescope that you can pick up with one arm and take out to the backyard for some impromptu observing. Several of us who have larger telescopes also own one or more smaller "convenience scopes".

After about eight years of using copyscopes, I decided to get something that would provide higher magnification, thus extending the range of my impromptu observing. What follows is both a product and mail order supplier review.

I had long admired the sharp, high-contrast images provided by refractors, and over the years, the proliferation of light pollution near my home has made image quality somewhat more important than light gathering. While a small apochromatic scope such as the 4-inch Tele Vue Genesis would be ideal, it was clearly beyond my budget. A lesser alternative was the Meade Model 390 - a 90mm, f/11 refractor that offered close to the light gathering of a 4-inch (102mm) at a price between $400 and $500. Since my copyscope was mounted on an equatorial mount with a heavy-duty camera tripod, I didn't need a mounting; however, all the suppliers initially contacted carried the Meade scope only with a mounting. Shutan Camera in Chicago sold it at $460 with an altazimuth mounting. But it pays to shop around. Wholesale Optics in Connecticut wanted only $399 for the same scope, and they suggested that for only $50 more I could get it with an equatorial mount. When I told them I really didn't need a mounting at all, they said they had one without a mounting that had a few scratches on the tube, but otherwise included a finder and diagonal, and I could have it for $279. That's when I dug out the old credit card!

In a couple of weeks, the scope was at my doorstep, but they neglected to send the finder and diagonal. A quick call netted an apology with an assurance they'd send out these items right away. (I received them ten days later.) In the meantime, I used the homemade diagonal from the copyscope. But the images were awful! It turned out that the diagonal was slightly misaligned. In the fast copyscope system with its broad cone of light, that misalignment wasn't noticeable, but at f/11 it became critical. An adjustment of the diagonal improved the images, but they still looked slightly out of focus at higher power. Star images had tails on them which flipped 90o as you passed through focus. The "blown-up" out-of-focus images clearly showed the diffraction rings, but the images were oval shaped. This looked like a classic case of astigmatism! On deep sky objects, the scope did show promise. M13 was just resolved at 110x, the Dumbbell Nebula (M27) showed up nicely even without a filter, and with an Oxygen III filter from our darker site in Hebron, both loops of the Veil Nebula were obvious (though lacking in detail). Could the image problem somehow be the result of the homemade diagonal?

Alas, when the Meade diagonal arrived and the scope was retested, it still showed the astigmatism. When I called Wholesale Optics that very night and spoke to the owner, he didn't seem surprised. He explained that in order to keep prices low, Meade has these lenses made in Taiwan, but the more expensive Japanese lenses are much better. He suggested that I'd be happier with a Celestron 80mm refractor, which uses the Japanese lenses. He offered a refund or an even swap for a Celestron Firstscope 80, but without a diagonal, owing to the higher cost of the Celestron. Several months ago, Sky &er Telescope had done a product review of starter telescopes and had noted that although the images were brighter in the Meade 90mm, the images were sharper in the Celestron 80mm. This seems to have been confirmed. Back went the Meade, and I awaited the Celestron.

Three weeks later, the 80mm arrived, with a finder. There was no cradle for attaching to the mounting, as I had thought there would be, but that was an item that's easy to make for yourself. Surprisingly, despite being a smaller scope, the Celestron was slightly heavier than the Meade. A backyard test showed that the images were typical of a refractor - beautiful! M13 was just resolved and the eastern loop of the Veil was barely visible with an OIII filter. Though objects seemed fainter than in the 90mm, they were crisper and easily snapped into focus. The Cassini division of Saturn's ring was visible intermittently, as was a cloud belt. Using Vega for an out-of-focus star test showed that the image was perfectly round with textbook diffraction rings both in and out of focus. The only imperfection was a few very short spikes on the circumference of the image. This scope was a keeper!

One thing I discovered was that the longer focal length refractors were very shaky on the same mounting that had held the copyscope steadily. This was surprising because the copyscope is heavier than either the Meade 90mm or the Celestron 80mm. The difference lies in the longer tube. Remember the lesson on moment arms from your high school physics class? Movement at the focusing end of the scope resulted in a case of the shakes right down the legs of the tripod. In addition, looking at objects high overhead required getting down on your knees. Using six 1x2x60 oak strips, I made a tripod that's about a foot higher than the camera tripod. Although it doesn't fold up as compactly, the vibration is greatly reduced. Together with the longer telescope tube, this makes the whole setup a little less portable than the copyscope. But, hey, everything is some sort of compromise!

Finally, an observation about the supplier: Wholesale Optics appears to be a reliable firm with very competitive prices. When you phone them, it's obvious that they don't have a lot of time to chat about the different products unless you're ready to make a purchase. If you order anything out of the ordinary or a little different than what comes "out of the box", then it would probably be a good idea to send a letter confirming your understanding of what is and is not included.

Published in the October 1994 issue of the NightTimes