Cal Poly 18 Bulletin 06
2012-01-08: Focuser/Rotator and Shelter
Since late October, work progressed at a much reduced rate due to the death of my (i.e., Richard's) father-in-law at age 95 years. As a result, I spent much of November and December in Connecticut. However, we accomplish two important goals: 1) the creation of an automatic focuser/rotator assembly to rotate and focus the CCD camera 2) the construction of a roll-off shelter to house the Cal Poly 18 during its operational shake-down!
The breakthrough for the focuser/rotator occurred when I remembered that years ago I had purchased two large-diameter spur gears. They are shown above. I sent this picture to Dan, and he immediately said, "Send them to me." So I went off to Connecticut and the gears went up to TMS. Continuing...
The next step was Ed Harvey's design for the focuser/rotator. One of the gears is mounted inside the focuser panel on a ball bearing, and turned by a small motor. The Feathertouch focuser rides on the bearing insert, and is driven by another small motor. Both motors are controlled by a SciTech controller. The unit has been tested; Dan posted a video on YouTube; you can see it at: http://www.youtube.com/watch?v=djMh5uAHtmU
I constructed the roll-off shelter while Eleanor was in Connecticut and I was home. Even though rained almost every day, I was able to build it in our shop building, in the dry. The shelter is seven feet long, four feet wide, four feet high at the back and five feet high at the front. The frame is made of 2x4s reinforced with 18 mm plywood gussets, and the side panels are 5 mm panel material. I chose this stuff because it is light in weight and inexpensive. The view above shows the partially completed shelter. To complete it and make it rain-proof, I added an "umbella" consisting of three eight-foot lengths of white corrugated polycarbonate plastic. The umbrella is 1.5 inches above the panel roof. It will reflect sunlight, allow air to circulate between the umbrella roof and top panel, and shed water.
Here you see the shelter rolled on 16-foot long tracks over the future location of the Cal Poly 18. The telescope will sit on asphalt driveway surface. You can see the "umbella" roof over the 5 mm panel roof. The shelter is close to the garage on my house for easy access during testing. (In the background is our "shop building.") The shelter received one primer coat and two coats of good-quality semi-gloss acrylic house paint.
Here you see the shelter rolled off all the way. At present, I put my 10-inch f/6 Dobsonian where the Cal Poly 18 will go. The trees at this location block the eastern and northeastern sky nearly to the zenith, so we'll probably end up with some wacky pointing models. But a sufficiently large swath sky is visible to test four- to six hours of tracking at equatorial declinations. This coming summer, I will move the telescope to a site near Alpaca Meadows Observatory, roughly 300 feet from the house in the middle of a 5-acre pasture.
We expect to test the Cal Poly 18 at TMS sometime during January 2012 , weather permitting, and hope to have the telescope in the shelter soon after we verify that all systems are GO!
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