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Telescope Building with John Dobson (1:28:30)


soundwave

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I found the mirror grinding part interesting, not so much on the building on the telescope. Not sure I'm a fan of his secondary mirror system as a whole, but if you are doing things on the cheap and simply I suppose it works.

John

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That made me wince :)  Along with just throwing the blank onto the ground.  There are some lovely quotes in it too though.

"There is nothing you can do in this class that we can't get out of.  If you drop your mirror and break it, you were supposed to do it the first day."

James

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What I like most about it, it is how he has to correct the focal lenght, becasue the process does not work perfectly at first. I find this a major problem with most tutorials, they show only things going right.

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He talks a lot about "one thousandth of the thickness of saran wrap".  I knew that was thin (saran wrap is, as far as I'm aware, the US equivalent of cling film), but it didn't really mean much to me in real terms, so I looked it up.

Saran wrap is apparently around 12.5um thick.  One thousandth of that is therefore 12.5nm.  Depending on which end of the spectrum you look at that's around 1/30th to 1/60th of the wavelength of visible light.

James

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