Quote:
Originally Posted by Ross G
Hi,
My first mount was a HEQ5Pro. It gave me 2 minute unguided exposures with a 650mm focal length. It autoguided for 10 minutes with no problems.
I then bought a Vixen SXW thinking I was upgrading. No way...!
Unguided exposures of even 30 seconds had bad periodic error.
I managed to get the autoguiding to work for 10 minute exposures by having the DEC Backlash at 90-95%. Admitedly, I can push these exposures to 20 minutes and they are still ok.
I have always thought the problem was too much backlash in the DEC axis. When I have slewing at the slowest setting I normally have to keep the Dec buttons pushed for 10 t0 20 seconds before the mount responds.
However, if the problem is actually in the Starbook, then maybe this modification is worthwhile. As I said before, the SXW mount has a certain quality that makes me want to persist with it.
Matt, I would be very interested in how your modified mounts work out.
Thanks.
Ross.
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The SXW has a problem with the dec axis. It is due to the fact that the mount has no roller bearings relying on closely machined tappered plain bearings in the cast which tend to be a bit sticky. You cannot get any decent tesion on the bolt holding the axis in place without locking the thing so they don't behave well there either. The SXD has bearings throughout and does not suffer from the same problem. The bearings are also the reason why the SXD can carry more weight than the SXW as the drive motors are actually much smaller on the SXD.
Mark