Thread: I fixed it!
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Old 03-07-2019, 04:33 PM
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codemonkey (Lee)
Lee "Wormsy" Borsboom

codemonkey is offline
Join Date: Jul 2013
Location: Kilcoy, QLD
Posts: 2,056
Originally Posted by multiweb View Post
I reckon it was due to the primary temperature not being uniform. You might have had a hot or cold spot under the fans maybe. I had similar issues by applying gentle heat to a newt primary. Unless it's evenly spreadout you get those temperature differentials that causes stress in the glass and it translates to wonky star shapes.
Definitely possible in some cases, but unlikely in mine.

I opened up the observatory, pointed the scope towards the sky and left it for an hour or so to cool down... never turned the fan on. Fiddled around for a bit, ran auto focus got a HFR of about 1.3px. Turned the fan on and ran AF again and got a HFR of over 2px. Then I noticed the elongation. Turned the fan off again, ran AF, HFR of 1.18px, no elongation... proceeded to image for hours with no on-axis elongation (off-axis is another story, as I mentioned above)

The fan was on for all of a minute or two, I don't think it was on long enough to deform the mirror and when I turned the fan off, I don't think it was off long enough for it to have recovered from that if that had been the case.
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