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Re: Aluminum Tubing

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Posted by Todd Hansen/">Todd Hansen on July 18, 1999 17:16:11 UTC

: Is Aluminum tubing a good choice for a 10" dobson? Also, where is a supplier of this tubing? thanks for any help! : John

John,

If your still looking for an answer to this question, and I don't think you were speaking about a truss assembly as the other two answers referred to, but a solid aluminum tube. May I suggest for anyting smaller than a 12"inch Dobson you stick to concrete pouring forms as Dobson himself uses. Metal tubes years ago (the 50's and 60's) got a bad name for tube currents. You use to see discussions in the literature of the time about insulating the inside of the tube with cork or felt to prevent this. I believe the reason this occures with metal tubes is the tube cools off much faster than the mirror, leaving the glass warmer than the air in front of it in tube. Currents would tend to vent up the inside of tube for hours until the the glass reached the same temperature as the outside air. I personally feel tubes are superior to open truss configurations in smaller scopes (12 inches and below) for virtually any reason you could talk about. You can of course get pouring forms by looking in the yellow pages under construction supplies. If you still think you want a metal tube, I would look under irrigation supplies, you might find thin wall aluminum tubing there in sizes up to 12 inches diameter but it won't be cheap and it will be a lot easier to find if you live in a place they do a lot irrigation like my state of California.

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