On The Road With the Super Heavy Duty 20” Telescope

by Allan Guthmiller

This article will describe some of the features and discuss how the telescope is assembled in the field. The telescope can be towed behind a standard full size pickup truck. The combined scope and trailer weigh approximately 2,600 lbs., is well balanced, and tows straight as a string down the highway. With the articulation point near the middle, it is quite maneuverable into tight areas of 40 ft. in diameter, such as seen here at one of my favorite observing site near Caliente, NV.

The trailer and scope travel uncovered, which causes a lot of strange looks from passing motorists. Eliminating a cover saves setup time, however, all the important parts of the scope are protected. The telescope has been thoroughly road-tested over rough terrain and has even survived golfball size hail. It’s hard to put dents into ½” cast iron! Another point I would like to mention, of which some of you might find disturbing, that the optics travel in the telescope! However, they are sealed in specially made protective casings. Again, I did this to reduce setup time and to avoid handling 70 lbs. of expensive glass in the dark. Surprisingly, the optics remain well collimated during transport. I check the collimation with a laser, and only on occasion I have to tweak an adjustment screw.

Setting up the telescope is fairly simple. I start by pointing the front end of the trailer within 10 degrees of north. I use a simple compass to make the adjustments. Four jacks raise the trailer until the wheels are off the ground and the frame is leveled.

Afterwards, the tie downs are then removed. There are several of them made of heavy duty chain, turnbuckles, eyebolts, and “U” clamps to secure the telescope to the trailer. This is due, in part, to curb one of my greatest fears of having 1,200 lbs. of telescope come crashing through the back window, should I have to slam on the brakes!

Next the base of the telescope is tilted up for polar alignment. Although the scope and mount weigh over 1,200 lbs., the load is almost perfectly balanced on the cross beam of the trailer, which acts as a fulcrum. To begin raising the mount requires lifting only about 75 lbs. of effective weight.

Once the mass of the instrument shifts over the fulcrum no further lifting is necessary, and the south end of the base settles gently to the ground. About 65% of the instrument’s mass rests on the crossbeam while the south end of the base supports the rest. There are no hinges connecting the mount to the trailer, but there are metal stops welded in place to prevent the base from slipping too far on the crossbeam. The base is free floating which aids in polar alignment.

Polar alignment is a snap. I use a Super Polaris Finderscope that mounts onto a block attached to the yoke’s south end. This block is machined so that accurate alignment can be maintained. Alignment takes only a couple minutes, and yields very little declination drift over a 20-minute period.

A pair of modified electric trailer jacks moves the south end of the base in altitude and azimuth and is operated by a push button control box. As mentioned earlier, the base is free floating, which allows it to be manipulated on the crossbeam without binding. The altitude range of the mount is between 0 and 52 degrees and an azimuth of 20 degrees, which permits use of the scope in any part of the United States.

White boxes on each side of the trailer contain all the equipment and tools necessary to operate the scope. The lids fold outward and act as a bench top to place equipment on. Some of the “Film” photography gear include a Lumicon Easy Guider, Olympus OM-1 35 millimeter camera, SBIG ST-4 Auto-guider, Vista Instruments dual axis drive corrector, Lumicon Sky Vector digital setting circles, and a Telrad finder. Many of these items have been replaced since I have converted to CCD imaging. Currently, I operate an SBIG ST-2000XM CCD camera that has a self-guiding chip built in, eliminating the need for the ST-4, Easy Guider, and OM-1 camera. The new system and guiding are controlled via laptop computer.

Actual setup time is about 40 minutes, 10 minutes longer than my intended goal. This is okay however, because the telescope is truly a pleasure to operate and well worth the extra time setting up. I hope this article will inspirational to others who are contemplating building a large scope for astrophotography.