Re: Dec Drive, etc.

[<aah@nofs.navy.mil>]

Well, those are not all of the problems of course.
  The Dec drive has considerable slop and even if
power remains on, you can move the telescopes several
degrees by hand before you feel the stepper.
So if you want accurate positioning, even the
changes you mention are not sufficient.
  Part of the focus trombone movement skew is due to
the bearings, part is due to the attachment to the
camera head, and part is due to the off-axis push/pull
of the lead screw.
  The CCD sequencing proms need work to lengthen the
vertical transfer timing (since I think there are CTE
problems), and to include true overscan columns so I
know where 'zero' is.
  The side plates need to be stiffer and the connection
to the horizontal bars needs to be stiffer as well; otherwise,
things move in the wind.
  The RA limit switch needs to be turned 90 degrees and
placed near the center of travel so that you can run both
the transit-singledeclination scans or the all-sky survey
modes like I'm doing.
  The initial block-done signal needs to be initialized
properly.  You've mentioned you have a fix; it just needs
to be implemented.
  You need a more permanent design for both the lens shades
and the camera bellows.  We will have some lens shades in
a couple of days and will pass on the construction information,
but the camera bellows will remain in their cardboard configuration
until I get back from Europe.
  The shutters concern me a bit.  I've had them stick partly
open on a few occasions, and the idea of over-closing them
makes me feel that the wires will eventually wear.  No solution
here, just an observation.
  These items are not meant as complaints about the Mark IV,
but just finishing details to get things to work properly.
Arne