The great balancing act: Stabilizing telescopes at the George Observatory

Editor’s note: This post is part two of our three-part series on how you helped us Save Our ‘Scope at the George Observatory. Read part one here.

Many have asked us how we are still using the large research dome at the George Observatory while the 36-inch mirror is in Iowa getting fixed. The simple answer is that we are continuing to use the 11-inch refractor, which is mounted on the side of the 36-inch telescope. The refractor has near-perfect lenses and is an incredibly high quality instrument in and of itself. The 36-inch mirror is best used for deep space objects, and the 11-inch refractor is best used for closer objects like we find in our solar system. Together, they work in tandem to make a remarkable team to view near and far.

The entire telescope grouping and mount weight approximately 10 tons. The 36-inch mirror weighed almost 500 lbs with the mirror and the center hub that holds it in place.  Because everything is so perfectly balanced, the motor to run the telescopes is approximately the size of a sewing machine motor. This delicate balance is also what keeps the telescope working properly. When we removed the more than 500 lbs. for the primary and secondary mirrors, the entire system was totally out of balance.

We were advised that glass is the same density as cement by our mirror expert.  With this piece of information and the help of Tracy Knauss, Paul Halford and Chris Randall, a plan was devised to make an exact replacement of the glass mirror out of cement. Paul located the materials and then Chris took over the project. He had scales and tools at his home and handily went about making the cement mirror.

First, Chris started with some rebar and a 36-inch sonotube.  

SOS Cement mirrorThen Brazos Bend State Park provided a fork lift to get it out of the truck.

SOS Cement mirror 2

SOS Cement mirror 4Then we had to get the 500-pound blank inside the building and placed underneath the dome so that it could be lifted three stories up into the dome and then installed.

SOS Cement mirror 6Here is the cement mirror blank installed in the real mirror cell.

SOS Cement mirror 9Finally, Tracy and Chris installed the cement blank into the back of the telescope casing where the real mirror will eventually be. By replacing the weight almost exactly, only a very few adjustments had to be made so that it was back in balance and able to support the 11-inch refractor again. 

With Jupiter, Mars and Saturn so prominent right now, this is the best ‘scope for viewing until the 36-inch returns to the George Observatory.

Save the Date: The George Observatory’s 25th Anniversary Celebrations
October 10, 2014: Members and donors event 
October 11 & 12, 2014:  Anniversary weekend. The Observatory will be open  from dusk until 11 p.m. Come look through the newly refurbished 36-inch Gueymard telescope that you helped save!

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