Reply #18 on: December 22, 2013, 03:07:00 PM
Rubber support for tilted CCD:
I have read this topic with interest. I just discovered that my QHY8 from 2011 had a tilt of 0.5 mm!!
On one side, I measure 6.0 mm between front and the CCD glass and the
other side 6.5 mm. CCD inspector also indicates a linear tilt in
pictures from my brand new APO astrograph.
Initially I was
preparing to use some aluminum foil as indicated but I discovered that
I could push the cold finger down. In the old design only the foam in
the front is developing some light pressure on the CCD. I my case it
was not enough to keep the CCD and finger in place. Also the foam under
the cold finger is pushing the other way. I newer designs this seem to
be improved by three plastic spring loaded pins. My QHY8 has the three
screws to mount the CCD on the cold finger only. The cold finger is not
screwed but only pushed against the peltier.
that the stacked peltier, cold finger and CCD are all machined well at
not thecause of the tilt, I decided to improve the cold finger support
and added some strips of foam rubber beside the CCD, so that the front
is pushing the cold finger on the peltier. The peltier is then pushed
against the back side. It works very well and I measure now symmetrical
distances of about 6.4 or 6.5 mm. So the tilt should be gone or almost
The rubber strips are loose inserted. The pressure is enough to keep them in place. See attached picture
I should have noticed the tilt much earlier. Too many of my pictures are not as they should be and I was blaming the optics.