Book Mania

Saturday, August 23, 2014

Why You Should Consider A Small Refractor

Yerkes Observatory 40 inch Refractor
Ok, maybe you shouldn't get a refractor, you'll never get one the size of the great Yerkes Observatory 40 Inch Refractor. But I'd have to say you should consider getting one, albeit a much smaller one. Let me tell you my experience with refractors to help you see why.

I've had a few interactions with refractors in my 5 decades of astronomical interest. I never owned one when I started, back in grade school and high school. I was intensely interested in astronomy for as long as I can remember. I read every book on the subject when in grade school (yup, both of em). But except for a couple of more or less toy telescopes, I never had one of consequence until high school.

Starting Out, No Refractor For Me

Not that I didn't want one. I wore out the pages on my Sky and Telescope issues, primarily trying to figure out which Unitron telescope to purchase. After every day-dreaming session, I'd always end up in the same place -- I could only afford their 2.4 inch Altazimuth model. The trouble was, all my books said I needed at least a 3 inch telescope for any serious viewing. Who doesn't want to be serious, right?

So my next option was to make my own telescope. I dug though every issue of each new Edmund Scientifics catalog, looking for objective lenses, aluminum tubes, focusers, and finders. It was always tempting to spring for all those parts, but once I added them up, I was again always running into a budget wall.

Even so, I bought many Edmund publications about telescopes and observing, like their informative Telescopes You Can BuildHow To Use Your Telescope, and even Photography With Your Telescope. Amazingly, they're still around, very inexpensive, and still good reads. Like with my magazines, I nearly wore out the pages in these paperbacks, planning and re-planning which telescope I was going to build, and what I'd see with it.

But all through high school, I never followed through on any refractor purchase or construction project. Big plans, little time, less money. I did lay my hands on a 6 inch Newtonian with my high school Principal's help, but never a quality refractor.

First Refractor Experience -- A Big One

However, my exposure to refractor telescopes changed when I went to college. I went to what was then a small college called Fort Hays Kansas State College. And sure enough, they had an observatory with what seemed to me a gigantic telescope. It was a 10 inch, long focus refractor built by Lohmann Brothers in the 1930's. The Lohmann factory built quite a number of similar sized instruments in that era.

The 10 inch refractor was a smaller version of the great Yerkes observatory 40 inch refractor shown at the article beginning. Though clearly smaller than the 40 inch, the 10 inch at my college was mounted on a large pier, was very long, and the eyepiece height above the floor varied greatly depending upon the target. There was a rolling set of steps that also worked as an observing seat. I could roll the contraption into position, and climb to the level that got me to the eyepiece.

I managed to get a lot of time on that telescope. Mainly because I expressed intense interest in it, and did a lot of begging to the head of the Physics department. I got to operate the telescope on open house nights, and for science classes. But I also got to use the telescope for my own clumsy efforts at lunar and planetary photography. It was an experience that I'll never forget.

Sometimes, I and a friend would just spend a couple of hours observing the intricate details of the moon that this behemoth made available. Even though by my junior year I had a 10 inch home constructed Newtonian telescope of my own (I purchased the mirror pre-finished for $100), it could not deliver the high contrast and exciting views provided by this great refractor.

The school now has a much newer telescope, a modern Cassegrain reflector mounted in its own obsbervatory. But the school had the foresight to keep the old, historic refractor in operation. And in a recent contact with a professor at my alma mater, I learned that on open house nights, the big line still forms to see the old classic refractor, and far fewer people line up to see the new instrument. There's something majestic and mysterious about those early 20th century refractors.

Next Refractor Experience - A Superb One

Still, in that college period, all of my own telescopes were Newtonian reflectors for budget reasons, and I still didn't own a refractor of my own. My next experience with one was during a summer when I got to work as a summer employee at the University of Arizona. Then I got to assist in using the Mount Lemmon Observatory 60 inch Cassegrain telescope. Now that was a telescope.

Okay, the 60 inch isn't a refractor. But on each side (left and right) of the big reflector was a 6 inch refractor mounted as a finder telescope. Yeah, you got it, 6 inch refractor finder telescopes.  With one on each side, one would be within reach no matter where the telescope was pointed. And on one occasion, when the telescope was between photographic targets, we used it to to take a peek at the moon. My first view was through one of the 6 inch finders.

It knocked my socks off. One of the best views of the moon I'd ever, or have ever, seen with a similar sized instrument. It hit me then what all the refractor praise was about from many enthusiastic amateur astronomers. Superior contrast, steady images, it all was there to see. The view through that 6 inch finder was far superior to those of my high school era procured 6 inch Newtonian.

Of course, I was observing then from about 9,000 feet. My old 6 inch reflector never saw through such a thin atmosphere.

Next Refractor Experience -- A Little, Big Surprise

A few years after that, a friend and I had our telescopes set up in my back yard. At that time I still had my Aperture Fever driven college era 10 inch Newtonian. My friend had set up a modest 3 inch refractor he'd constructed from surplus optics, similar in appearance and size to the Orion model shown at left.

When I looked through his refractor, I was stunned. The contrast of the image made Jupiter's belts stand out much sharper than even my 10 inch Newtonian showed. Sure, some details were visible through the 10 inch that the 3 inch couldn't match, but the 3 inch view was more eye catching, steady, and pleasing somehow.

I wanted one.

But years went by before I ever sprang for a refractor. When I did spring, I went for what I thought was a bargain: a Meade 90 mm f/10 refractor on an equatorial mount. How could I go wrong -- it was a big brand name. But alas, what I had bought was an imported telescope, made in China before China made high quality optics. I should have realized that the price was so low for a reason.

As an example of its low quality, I tried on many occasions to see  the Cassini Division of Saturn's rings with it. It wouldn't reveal the division. I since have obtained and used a Meade ETX 90 on Saturn that has easily revealed the Cassini Division, so the 90mm refractor just wasn't up to it even though the ETX 90 had no aperture advantage.

While I can't complain about the mount on that 90 mm refractor, the views through the instrument were much less than I'd hoped. Not at all comparable to my friend's 3 inch that was made from surplus optics. So I figured right then that I still couldn't afford a quality refractor, and still wasn't interested in building my own.

Bringing It Home At Last

Then some years later I joined a little astronomy egroup on the web. The group was dedicated to small refractors, 60 mm (2.4 inch) being their favorite. I read entertaining and almost unbelievable reports on views though various 60 mm telescopes.

It left me scratching my head. What about the sacrosanct 3 inch rule? I finally asked the group what they'd recommend that I try to obtain.

They listed primarily old brands, often of Japanese make, most of which were no longer produced. They were though readily available at garage sales and Ebay. The general sense was that in the 60's and 70's era, 60 mm refractors were not made to be toys, but serious introductory instruments. They were telescopes with good optics and solid construction. I looked on Ebay, and sure enough some were available. But not as cheap as I'd hoped.

One club member dug through their orphaned telescope collection and donated a telescope to me. It was a 60 mm Monolux of Japanese design, likely decades old, that needed some tender loving care. I reviewed my experiences bringing this orphan back to life here.

Once I'd waded through the problems, like discovering that one objective lens was in backwards, and solving the astigmatism issue, I found this telescope to perform far better than I'd ever expected. From my first views through my college's 10 inch to my more recent views through a quality 60 mm, I was impressed. Having a long focus refractor of quality seemed to serve up very pleasing images almost regardless of size. More details in bigger telescopes, of course. But pleasing views, always.

So here in my old age I find that the 2.4 inch (60 mm) Unitron that I'd almost bought many times in my teens would have thrilled me. I'd have probably worn it out and been on my 3rd one by now. Since refurbishing the Monolux 60 mm, I've constructed (yes, I finally built a refractor) a longer focus Carton 60mm Telescope. At left you see an example of what it can do.

So at this point, having exposed my sparse but varied past with refactor telescopes, I strongly suggest that you don't let the telescope snobbery keep you out of the game. If you're just getting started, or know someone who is, don't be afraid of getting a 60 mm to 90 mm refractor, something like the Orion 09882 Observer 70mm Equatorial Refractor Telescope. What you'll have is a telescope that can deliver high contrast steady views, is small enough to be easily portable, and requires very little maintenance for all that. Just get one with solid construction and a steady mount.

It's hard to go wrong with these long focus types. The long focal ratios reduce color fringing, a nagging characteristic of refractors, to a very tolerable level. Just don't count on that being true if you buy an inexpensive short focus refractor. If you want to go inexpensive -- go long.

So what if you're more into wide field observing? Wouldn't it be handy to have a telescope about 18 inches long, perhaps some 60mm to 80mm in diameter, for star observing? Light weight, portable, wide field, low maintenance -- is it possible?

Yes, it is possible. But for precise, color corrected images, the price goes up a bit. To get good color correction and sharp images out of a short focus refractor, you can't get away with the classic crown and flint glass achromats. You have to go to the ED optics design, which use more exotic glass compounds that minimize color dispersion (translate to color fringing).

If the short focus, wide field, portable telescope is what you want, a perfectionist version would be like the ED Triplet shown at left. Short, wide field, 80mm star pulling aperture, and yes -- higher price. You don't need to pay that much if you get an ED doublet, like the BARSKA Magnus ED 560x80 Refractor Telescope at half the triplet price.

If you're satisfied with low power and a bit of color distortion, you can even try a classic achromat short focus instrument like the Orion 9946 ShortTube 80-T Refractor Telescope, which comes it at less than $200. You'll still get pleasing wide field images, but may see a bit of color fringing on the brightest objects, and may find less clarity at high magnification.