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Old 28-09-2020, 05:14 PM
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LewisM
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LewisM is offline
 
Join Date: Aug 2012
Location: Somewhere in the cosmos...
Posts: 9,988
Restoring a $150 Skywatcher ED80 refractor

Recently, an old gold-tube Skywatcher ED80 was offered here, advertised as "foggy optics" and scratched tube plus a few other quibbles for $150 posted with the rings and dovetail bar. It was worth taking the gamble to me so I struck the deal. See picture 1 and 2 for the seller's pictures through the scope. Not good.

Hoping it was just salt or condensation between the elements, I took off the dewshield cap upon arrival with trepidation. Optics looked ok, but the smell of old electrical tape (holding on the dewshield cap and the dewshield itself acting as a shim around the cell) had me suspecting off-gassing of the glue was vapor-depositing onto the objective. Time to disassemble that cell and clean the glass. Big inhale...and hold...


Got out the retainer ring spanner, but found I didn't even need to - the ring was on finger tight. OK, odd. What was even more odd was I was confronted by the weird sight of the element spacer foils on the OUTSIDE of the front element - a "HUH, WTF" moment. Curious indeed. Placed a thick wad of felt onto a cat-food can, and pushed up the objective, knowing in advance I should be REALLY leary about the front element.

Sure enough, as per my diagramme below, I was confronted by an objective arrangement that had been completely and utterly incorrectly reassembled by someone. Well, there you go, that accounts for the under-performing refractor. No wonder it wouldn't come to focus and look foggy.

I gave the glass a clean with Pursol anyway, and reassembled it the correct way. I then tested the optics on a garage near by. A little better I must say (pic. 4 - taken with my iPhone dangling unaligned over an eyepiece - very scientific)
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