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Damaged Optics - need help please

Started by Demetrios Papadopoulos, 10/10/2005 11:33PM
Posted 10/10/2005 11:33PM Opening Post
I had a mishap with my Hardin 10" dobsonian. This has a Swayze refigured primary and protostar secondary.

While readjusting the secondary, I dropped the holder with secondary onto the primary! The secondary is not visibly damaged. The primary has 4 superficial scratches into the coatings, the largest of which is ap. 3mm x 6mm.

After the mishap, the star images are not pin point and have a small lateral flare when focused. With out focus in one direction the stars are tear shaped. With out focus in the other direction the stars have a concave, tangential line on the opposite side from the tear shape. I wondered if somehow the optics were pinched, and checked the primary mirror cell to ensure there was no pressure on the mirror.

Is the primary irreversibly damaged? Could the secondary be damaged also?

Thanks in advanced for your expertise.

I certainly have already learned a valuable lesson from this embarassing event. CAUTION, CAUTION, CAUTION WITH UNATTACHED OBJECTS ABOVE THE PRIMARY!!!

Demetrios

Posted 10/11/2005 03:46AM #1
Hi Demetrios,
It sounds like collimation or alignment of the mirrors rather than damage of the magnitude that you described. You might have caused the secondary to not sit properly in the holder. The holders are made of plastic and have just a small clip to hole them in place with foam rubber used as filler. I did not like the foam rubber and replaced it with a cotton like material of polyester. The holder can be too tight, but I would think you would have noticed that before.

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