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Log, Feb 9, 2007

12 people. Well, we actually opened for about a dozen people. We couldn't open the dome again, but we hauled out our Questar and saw some interesting things in a small scope. One spectacular event was the brightening of the famous star Mira in Cetus. Normally, Mira is so dim that it is either invisible or nearly so but every 330 days or so, it brightens more than a hundred fold and becomes a second magnitude star. Look in Cetus for a noticeably red star. It is in the southwest currently in the evening. Ernie thinks this is the third time he has ever seen this brightening of Mira, and as far as I can remember, this is my first time. Quite exciting. We also had one of the most astronomically aware young people I have ever met. Getting such intelligent question from a girl who can identify just about anything in the sky is a joy to my heart.

Well, I have some further bad news. The dingus which has failed is definitely not the famous "145-175 microfarad starting capacitor". Other suggestions by the manufacturer that it might be the control switch have just about totally been ruled out. We have established that the switch has continuity from the wall socket to the odd ball eight socket connector plug for all the eight wires that it includes. It is possible that above the plug the eight wires to the motor array have a broken connection, but testing this is doggone near impossible at the top of a sixteen foot ladder at the summit of an eighteen foot dome. [Try getting a firm footing on a ladder resting against a curved surface with an expensive telescope right below you!]

As far as we can see, this basically leaves two possibilities - something broken in the motor, or one or more of the eight wires snapped. Neither can be tested at the top of the dome. We know for a fact that the shutter MOVES easily, and that the gear box IS IN WORKING condition because hand turning the motor shaft raises and lowers the shutter (a few inches) without problems.

We must dismount the motor. This cannot be done on a ladder above the telescope without great peril to the telescope and the darn fool who was silly enough to climb the ladder. We must get scaffolding erected, disassemble the motor mount, lower the motor to the floor and proceed from there. Once down, we can check the wiring continuity. If it does not fail we can test the motor directly. My single best guess at this point, from talking with several knowledgeable folks is that we will find the motor is either burned out or more likely that its "brushes" are worn out. The motor will have to be repaired (or replaced) in these cases. Once the motor runs reliably again we reinstall it at the top of the dome on the self same scaffolding. And nothing can go wrong, go wrong, go wrong....

-Les Coleman

Leslie Coleman
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Leslie Coleman
Entry Date:
Feb 9, 2007
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Leslie Coleman's Log
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