Alachua Astronomy Club: Don Loftus

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Don Loftus and His Dobsonian Telescope

This page profiles a member of the Alachua Astronomy Club and his stellar handiwork

COPYRIGHT NOTICE

Pictures are copyright © by the author. However, these pictures may be reproduced for non-commercial usage providing credit is given to the author of each picture.

(All photographs by Donald P. Loftus)

Donald P. Loftus, AAC member, is also Coordinator of Broadcasting in the Division of Instructional Resources at the University of Florida. Although relatively new to astrophotography, Don produced some neat photos of Comet Hyakutake in 1996. Here he displays his talent with pictures of the Dobsonian telescope he and his son Curtis have been working on. Beautifully crafted, the telescope is not only great for looking through but its appearance also rivals superbly crafted furniture!

For more information E-mail Don at: dloftus@coe.ufl.edu

Figure 1. Curtis Loftus and The Telescope He Helped Build

It is a 6-inch, f/8 Newtonian and is a first time telescope project for both of us. Curtis and I made the mirror from a William- Bell kit. The mirror cell was made to allow the mirror to be installed and removed from the telescope to do star testing. It also allows Curtis to look at the moon before the mirror is coated.

The telescope is made from 30 strips of Cypress wood, glued to each other and to plywood rings that make up internal light baffles. The baffles also add strength to the tube assembly. The tube has five coats of polyurethane paint, with the last two coats put on with an automotive spray gun to get smooth even coverage. I used a Daisy Aimpoint as a finder and an Orion low profile focuser with a single vane secondary holder. The secondary is one inch across the minor axis and is attached with silicone.

The mount is also made of Cypress wood. Details are seen in the other photographs. The mount comes apart and makes set up and transportation easier for Curtis. The fork is mounted to the legs by a rod and rides on Teflon pads. As part of the legs there is a metal triangle that keeps the legs set to the right angle when they are open. The fork arms (made of Cypress) are attached to the bottom section using wood dowels and glue, so there are no nail or screws visible.

The clamp mount around the telescope is made from 3/4 inch plywood rings, cut to make them open. Rubber bands hold them closed. This allows the telescope tube to turn or move back and forth in the mount for balance and ease of viewing. I put black tape on the edge of the rings to hide the plywood end grain and make it look more finished. Felt glued to the inside of the rings provides a soft contact area.

This telescope and mount were designed without plans. I often made things up as I went along. Information from the Amateur Telescope Makers list serve was extremely valuable in making this project, as was the "ATM Gleanings" section of Sky and Telescope. My plan now is to turn the second 6-inch blank into a RFT scope and make it on the Weino bench mirror grinding machine, which I also have to make. This project was enough to get me hooked on making mirrors and telescopes. Ultimately I want to try making a 20-inch to 24-inch, one inch thick plate glass mirror, but want to make some other mirrors first. This has been a great father/son project and I recommend it for anyone who want to try. As they say on the sneaker commercials, "Just Do It!"

Figure 2. The Telescope and Mount Taken Apart

On the end of the folded legs, a rod holds the fork in place. The black section, which is difficult to see detail on, is the metal triangle that keeps the legs spaced properly when they are open. It is attached to the center leg. The white pads are the Teflon bearing surfaces. The pads on the fork need to be placed further up the curve and away from the center to provide more friction as the scope moves too easily in altitude.

Figure 3. The Open Telescope Cradle

The plywood rings were cut with a wood router and a circle attachment. The blocks of wood and the round trunnions to which they attach are made from Cypress. The trunnions were turned on a wood lathe and then coated with about four coats of polyurethane paint. They look really good and work well against the Teflon. Probably because the scope is so light, Ebony Star laminate was not needed as a bearing surface against the Teflon. Look closely at the ends of the open mount; you can see the 3/8 inch dowels to which the rubber bands attach. In the future I plan to alter the mount to allow a mechanism to push against one cross member. This would relieve the rubber band pressure on the tube enough to make the scope easier to move. At this time, I have to try to pry my fingers under the cross member or take the rubber bands off.

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