Re: Pride Goeth Before a Fall

[aah@nofs.navy.mil]

Tom wrote that there was periodic error in the drive.
I'm surprised at this, as the idea of a lead screw is
to cut the periodic error down by a factor of many, since
several threads are engaged instead of the single thread
of a worm gear.  I'd think about it some more to be sure
something else isn't mimicing such an error.

Yes, one can correct periodic error in software, but I'm
not sure you can do it with your setup.  A limit switch
will tell you the screw position, but to change the drive
VCO on-the-fly may be more command-intensive than the
Stamp can handle.  I'd much rather get the periodic error
out *now* before things are shipped (or other mounts are
built).  Can you go ahead with your plan of investigating
other screws, or at least try some other experiments with
the current mount to see if adjustments can get rid of
the error?

Stars that are 6x2 are not bad, but one of the purposes
of going to the custom lenses was to get good images.
You lose big time in the Milky Way where most of the
variables live, and the magnitude loss means you could
have used 300mm f/5.6 camera lenses instead.  Let's try
to get the mount fixed before shipping any systems.

Arne