Amateur Astronomy
David P. Anderson

We have a couple of telescopes and a great pair of Celestron binoculars and an occasional interest in star gazing, mostly on our spring and summer vacations to New Mexico and Colorado, where the skies are exceptionally dark. Our first telescope was a borrowed 8 inch f10 Newtonian reflector, which we set up in our back yard for a year. After that we bought a 60mm f10 refractor as a birthday present for my wife.

We made a number of changes to the refractor. We added 26mm and 32mm eyepieces and a 1.25 inch right angle adapter to complement the 20mm eyepiece that came with the telescope. We removed the finder-scope and replaced it with a Telrad reflex sight. This made the telescope much easier to use. After about a year we decided that the tripod that came with the scope was just too awkward and the adjustments too clumsy. So we built our own Dobson style refractor tripod, pictured above and below.

The tripod itself is made of redwood with a formica-and-plywood spreader, and extensible legs. The Dobson mount utilizes teflon pads riding on a formica surface for the azimuth rotations, and hard plastic rings riding on teflon pads for the altitude rotations. This combination produces an extremely smooth "buttery" feeling mount which is very easy to use. The telescope is balanced and requires no locking screws to hold it in any given position. The plastic and teflon bearings produce very low friction and, more importantly, the static and dynamic friction are nearly equal so that moving the telescope by tiny amounts is easily accomplished, without bumping it out of position.

The Telrad reflex site and right angle prism are counterbalanced on the bottom of the box which holds the telescope. The telescope itself is mounted cantilever fashion off center from the mount so that it can be pointed straight up at the zenith without interfering with the tripod legs. The whole thing is then counterbalanced with three lead weights mounted in the front of the Dobson base between the left and right side members. A piece of black industrial foam rubber pads the front of the telescope tube when it is in the horizontal position. The telescope, tripod and all, only weights about 15 pounds and can be easily carried out in the backyard for casual observing, when we don't feel like setting up the "big" telescope.

Here is a very young Jonathan stargazing in his pajamas with his red flash-light (so as not to disturb dark-adjusted eyes) and his observing notebook, sketching the craters of the moon. The combination of the reflex site and low-friction Dobson mount makes for a very intuitive telescope that the kids greatly enjoy using. (Sometimes I think it also does duty as some kind of Star Wars laser weapon.)

Our other telescope is a Meade 8 inch Schmidt-Cassegrain. This telescope has an f10 focal length in a folded optical path making the telescope tube only about a foot long. It is suspended on a pair of aluminum forks with a motor drive, attached to an adjustable equtorial wedge, all bolted to a massive steel tripod. We have several eyepieces for it, including 10mm, 18mm, 26mm, 32mm, and and enormous 36mm wide angle "Erfle" eyepiece which requires a special 2 inch right angle adapter. Views of faint deep space objects like nebula and galaxies, barely visible in the 60mm refractor, are breathtaking. We added another Telrad reflex finder in addition to the finder scope, both of which are usually needed for locating faint objects and star-hopping.

The bar and lead weight underneath the tube body are used to counterbalance the finder-scope, Telrad, and a 35mm camera we sometimes mount on top of the 'scope for time-exposure photography.

This 'scope is much heavier and requires considerably more attention to setup, polar align, and so on, but produces much sharper and brighter views than the refractor, which is more useful for lunar and planetary observing. We have over the years added a set of 35mm cameras and adapters for photography which the motor drive and careful alignment (and hand guiding) make possible.

Increase in light pollution over the past ten years in our neighborhood has made observing more difficult. This especially contrasts with the dark skys we see in New Mexico and Colorado, and the superb viewing experiences we have had in the Davis Mountains near Ft. Davis (home to the MacDonald Observatory and "Texas Star Party"). Most of the time both telescopes spend their days and nights shrouded in their plastic bags to protect them from dust and the ever-present bird feathers from my wife's 17 finches, parakeets, and doves.

24 August 2002
Dallas, Texas
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