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Large telescope project

A major project of the Astronomy Club has been the building of our ‘big eye’, a unique telescope.

In the mid 1990s the Davis Astronomy Club began building a telescope to accommodate an 18.5 inch diameter mirror that Mr. and Mrs. Graham of Davis donated in February, 1993. The major design criteria for the new telescope were portability and low cost. Back in the 1960s John Dobson pioneered the design for big, low cost 'light buckets,' as the these large popular telescopes are often called. Our club was fortunate in having a student of Dobson's, Tim Feldman, as a member. Tim designed and built our club's big eye. He was assisted by the club's founder, Dennis Smith.

Since the club had no dues, we were very careful with expenses. We received a generous gift of $100 toward the expense of building the telescope from Mr. and Mrs. Graham. Other club members pitched in over $300. With these gifts, we purchased three pieces of hardware: a focuser, a spider, and a secondary mirror. The focuser holds the eyepiece. The spider holds the 'secondary mirror' that reflects light from the primary mirror into the eyepiece. Because we could not afford a good secondary mirror (they cost between $100 and $300), our third purchase was a $20 front-surfaced mirror. We saved money on other materials by using stock aluminum pieces for mirror supports and for the metal truss poles. Most of the telescope is made from inexpensive blocks of closed-cell styrene foam glued between sheets of FRP glassboard. A local Davis hardware store (Hibbert Lumber Company) generously allowed us to purchase materials at their cost.

The telescope has two large lightweight circular bearings which are attached to an open-frame aluminum mirror box. The bearings ride vertically inside a shallow rocker box, and that pivots on a sturdy yet lightweight aluminum base. Removable hollow aluminum truss poles form the telescope's tube, and support a lightweight upper assembly (where the secondary mirror and focuser are located). When pointed at the zenith (i.e., straight up), it is approximately eight feet tall. Because the primary mirror weighs about 85 pounds, the entire telescope weigh about 150 pounds -- which may sound heavy until you consider that a traditional telescope of this size built of wood and Sonotube would weigh about three times as much.

The entire telescope can be taken apart into about a dozen pieces and transported in the back of a station wagon. It takes about 15 minutes to put it together and adjust it for a night's viewing. The heaviest piece is the mirror box; two people carry it like a litter, using a pair of stout wooden poles.

This telescope is special for many reasons beyond its large size and innovative design. It is the continuation of one man's dream that began over 60 years ago. In 1945 Harold Simmonds helped found the Sacramento Valley Astronomical Society (SVAS). The 18.5 inch mirror was made sometime in the early 1960's by this same man. Articles by Ina Tacke in the SVAS Newsletter regarding the history of the Society, show that Simmonds was a devoted amateur astronomer, a careful telescope maker, and loved giving the public views of the universe. He had a public address system, a slide projector, and several telescopes -- all of which were used to introduce large Sacramento audiences to astronomy. We also received a donation from a former member of the SVAS, now living in Dover Delaware, who recalled that Simmonds had given her the first telescope he had ever made -- a 10.5 inch.

Club members spoke with two people who knew Mr. Simmonds during the 1960's. One recalled the careful craftsmanship that Simmonds put into the 18.5 inch mirror. Another remembered that Simmonds put the mirror and its original telescope body (which has since disappeared) into a pickup truck and took it up to Wright's Lake to test it; and that it worked quite well. Both said that Simmonds's hard work and enthusiasm were inspiring. Unfortunately, with his death much of his property disappeared. We are very fortunate that his friend and fellow amateur astronomer, David Graham, rescued the 18.5 inch mirror before it too, disappeared. We are grateful to the Graham family for donating the mirror. The Astronomy Club's intent for the new telescope was that it would advance the goals that Simmonds and Graham shared: to introduce the beauty and wonder of the cosmos to everyone!

It took Tim and Dennis a little more than a year to build the telescope in their spare time. They set it up at various club meetings and star parties in and around Davis; it worked well and gave very nice views of distant galaxies and nebulae -- a real tribute to the quality of the mirror that Simmonds hand-crafted. Thanks are due to everyone who helped the club in this project, and most especially to the late Dennis Smith; Dennis was the real driving force behind the project.

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