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Ken Haydu
member
Reged: 12/21/08
Posts: 57
Loc: Southport, NC
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Re: New life for a 29 year old Astroscan
07/06/09 06:53 PM Attachment (15 downloads)
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Kenneth
The original foam was of no use anymore. I replaced it using the type of foam that is sold for use as both exercise pads and for laying under camping bags. Comes in a blue sheet 1/2" thick at Walmart's sporting goods section.
I used contact cement for a secure bond of the foam to the mirror, which appeared to be the original method
Once the disc of foam was bonded to the mirror, I used a sharp razor blade to trim it into the proper shape. This type of foam is more easy to shape than foam rubber, and also makes a nice liner for eyepiece cases as it is easily cut with a 1.25" circular drill hole saw, to make holders for your eyepieces.
The Edmund design uses the pressure of the slightly compressed foam to press the mirror up against the retaining ring. When the foam does this, the mirror is square to the tube and the mirror was in collimation.
The secondary mirror and it's holder is cemented to the glass window. There is no adjustment there, and if the secondary were out of alignment, it would be another chapter. Fortunately, the bonding epoxy that is used seems to continue to do it's job over the years; it is just the foam under the primary that gives out
Hope that answers your questions
Edited by Ken Haydu (07/07/09 01:17 PM)
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