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Ken Haydu
member
Reged: 12/21/08
Posts: 57
Loc: Southport, NC
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New life for a 29 year old Astroscan
07/02/09 11:54 PM Attachment (99 downloads)
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An older Cloudy Nights posting mentioned that a piece of foam rubber held the primary mirror in collimation, and I thought a few photos may interest the forum
This 1980 (made in USA) model showed flaring on stars, and I was aware that the primary was not correctly positoned.
An easy test to determine if the foam has lost it's support is to invert the scope and gently shake it. If you hear the primary moving, the foam most likely has seen it's day
Removing the circular spring ring holding the secondary window is fairly easy, as is removing the window. The window has a groove that mates with the housing, so replacing it leaves no guesswork
I cut a 4.1" circle of poster paper to cover the primary while removing the circular spring clip that holds it in place. The primary will lift right out of the tube
I had wondered about the thickness of the primary in these scopes, and was quite surprised to see that it is 5/8" thick
The grey foam that we are all familiar with has little resiliency after 29 years. You can see on the left where I pressed my finger into it before taking the photo.
After replacing the foam (gave the mirror a bath first), and reassembling the scope, a simple check with a lasermate was promising. Tonight I star tested the scope with a 9mm orthoscopic, and was rewarded with an identical pattern both inside and outside of the focal point. I count 3 diffraction rings and the same image of the central spot, and suspect it is a very good mirror.
I am aware that the 9mm only yields 49x in the scope
The writing on the back of the mirror shows the date (Nov 18, 1980), the diameter of the mirror (4.25"), and I can not quite guess what the 5/4 would represent?
I am so impressed with the improvement, that I now wonder what it would cost to have the mirror resilvered?
Well, that is my story. Perhaps this may encourage others to take a second look at that old Astroscan.
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