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RE: Help Again,

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Posted by Steve Fejes on August 3, 2000 01:16:58 UTC

An 8" diameter f/5 mirror will have a sagitta of about 2.46mm or 0.0969"

A 3/32" drill bit is 0.0938"

This would be a good depth to stop rough grinding.

You should consider making a longer focus mirror than f/5 for your first one. F/6 or f/7 would be easier to make well and would give you a better image with a smaller diagonal mirror. The telescope would not be very much longer or heavier.

I have an 8" f/8 that I love, it was easy to parabolize because it is so close to a sphere. If I had it to do over again, I would probably aim at f/7.

Jean Texereau`s book How To Make A Telescope is the best in my opinion. Willman Bell sells this. It is a step by step guide from a pro of how to make an 8" mirror and telescope. It is well worth the money. Many of us have used this book as our guide.

Steve

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