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Pinching in your refractor

Started by cysmarc, 12/12/2010 05:58PM
Posted 12/12/2010 05:58PM Opening Post
Hi,
Well the suject just about says it. I would love to know if anyone else's pinches, at what temps, and what have you done to fix it? It is not due to a lack of cool down and the retaining ring is not screwed down too tightly. I am trying to resolve it with Orion but the scope is out of warranty. (Though if it is pinching then that is a manufacturing defect and should be covered for life. It's not like something broke.)

Posted 12/12/2010 06:33PM #1
iTZ, you still dealing with this problem? Wow
You were taling about this 2 yeara ago.
I live in the same city you do and have owned, easy 15 refractors and have never had that problem.
If Orion wont take care of it then send the scope to someone who builds and knows refractors to look it over.
Posted 12/18/2010 02:36PM #2
I've seen two TMB 100mm F8 APO triplet lenses that pinched at
cold temperatures. Problem started somewhere around 40F with very
slight effects. By 20F things got pretty bad with obvious
spikes on bright stars. Problem was that the cell inner
diameter contracted faster than the glass, and sqeezed the glass
very tighly around the circumference. Obviously they want
tight clearances to keep the glasses centered, but these were
too tight. Fix was to have the lens cell machined-out to
slightly larger ID. The repair work was done under warranty
by some chap in Germany. Interferograms before and after were
pretty much identical, so the machine work doesn't seem to have
hurt anything.