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When Lightning Strikes
(7 August 2011)

  It's been incredibly hot and humid in Washington DC this summer, with temperatures hovering at or above 100°F for weeks. Because of the unstable air at the end of June, 2011, we had a series of really severe electrical thunderstorms pass through the DC area. These put our house and neighborhood in the dark more than once. The outage was, in one case, about 40 hours. If that were the only problem!

  One of the lightning strikes that did not kill the power was so close to the house that I could feel the hairs on my arms bristle. I experienced this once before, in Vienna (Austria) in 1968, when a bolt of lightning struck a flag pole or light standard only about 50 feet from me. The flash and crash were simultaneous, as they were here, too. It was wicked, and this strike had several interesting consequences.

  My family and I were sitting in our basement family room. A couple weeks earlier we had finished a much-needed basement renovation. We bought a new LED television, and we also upgraded the satellite receiver/DVR so we could get HD TV and view HD movies on it. Imagine the "thrill," then, of a flash and crash followed immediately by hearing a "pop" in the DVR and watching the colors on the TV fade away, leaving only a green-tinged ghostly image. Fortunately, it turned out that merely shutting everything down, waiting a few minutes, and turning it all back on restored the DVR and TV. We dodged that bullet, or so I thought...

  It wasn't until some while later - a couple of days given the continuous bad weather - that I got the really bad news! Three times over: 1) turning on the telescope seemed okay, but it sped away as LX-200's can do, with a run-away slew in right ascension - only turning off the power stopped that; 2) the computer would not connect to the telescope; and 3) the computer would also not connect to the Optec digital focuser.

  Luckily my Meade is not under warranty anymore. Lucky, I say, because I enjoy tinkering with electronic stuff like this telescope is made of. So I took the telescope off the pier, brought it into the house, set up the "lab" in the most functionally in-the-way place in the house, and poked around for four weeks with a DVM and oscilloscope, using a variety of the schematics that are available on the web in various places.

  It took me a week to fix the problem of the run-away. I'd had difficulties with run-away the previous Winter and fixed them (it was the reason I bought an oscilloscope). This time the problem was a flaky 5V voltage regulator that sits on a little circuit board attached to the RA drive housing. This little board is what tells the telescope in which direction and how fast to slew. I replaced the regulator, adjusted the comparator square waves, and that took care of 1).

  When I finally got through the problems with the run-away, it revealed another problem: 4) the NESW buttons on the hand controller did not move the telescope. All the other keys seemed to do what they were supposed to. Drat! I spent the next two weeks figuring this out, and it wasn't easy. The culprit was an internally shorted IC related to the CCD guiding port signals. This created an unstable microprocessor state, basically disabling the NESW keys. So that got fixed, too.

  The other two problems were caused by a different but identical fault - the IC that reads RS232 signals from the computer and translates them to CMOS levels for computer processing was destroyed by lightning - the devices couldn't "hear" the signals coming from the computer. ICs handling RS232 signals are particularly prone to fail from static electricity. Lightning too, I guess. Two new ICs later and these devices were both up and running.

  So now I've just put the telescope back on the pier, and I will have to take the next several nights to go through the whole realignment and recalibration process using PEMPro, PEC, flats, darks, and focus V-curves before getting back to business.

  In the meantime, I have to go out to the shed observatory and unplug everything - it's 98° and I hear the thunder of an approaching cold front.