As we discussed through private emails, the oscillation issue that you experienced is caused by the absolute encoders desperately trying to correct for the instability caused by substituting
a customized and inadequate counterweight shaft in place of the shaft that ships with the mount. The pendulum-like flexure created by multiple step-down threaded adapters to a very thin counterweight shaft is magnified by the counterweights set at the very
bottom of the shaft.
When you restore the supplied counterweight shaft to the mount the problem will go away. We take great pride and consideration of every detail when designing our mounts. Please do not try
to modify them.
Phone: 815-222-6538 (direct line)
Phone: 815-282-1513 (office)
On Behalf Of weihaowang
Sent: Tuesday, July 13, 2021 09:04
Subject: [ap-gto] Strange Mach2 RA oscillation.
I am at a remote site for imaging. This month I had used Mach2 several times without having any problems. But today, it suddenly behaves abnormally. The RA axis quickly oscillate for many arcseconds. The attached image is a screenshot from PHD2. As you
can see, stars become highly elongated along east-west even under an exposure time of 1 second. What puzzled me is that if I release the RA clutch knobs and only tighten them very very slightly, the problem goes away. If I further tighten them with hand
(not with any tool), the oscillation shows up. The mount is well balanced. I looked around and did not find anything (cables etc.) that can interfere the RA axis.
And as I am typing now, the problems goes away. I will try to image now. However, I hope people here can provide some guess on what happened, so I know what to do next time this problem shows up to either solve it or diagnose it.