I just remounted my OTA after moving the guide scope to the accessories bar.
That made it a lot heavier on the head side of the RA balance. So I rebalanced
the RA axis by moving the counter weight out another inch and a half or so.
About the thickness of the weight. (I hope I have RA and Dec correct here. RA
== rotating around the polar axis?) The head rotates around the RA axis fairly
freely. So I think I got a reasonable balance now for the new configuration.
Until I pick a target, I can’t implement a bias though. And I’m not sure the RA
axis is free enough to implement a slight imbalance for some definition of
“slight”.
However! The Dec axis is very stiff. It seems to move more freely in one
direction than the other. But both directions are very sticky. Maybe that’s why
I see a sawtooth pattern in Dec plot in PHD2 when guiding isn’t cooperating?
But why is PHD2 mucking around “correcting” Dec in the first place? My
understanding is that for a “perfectly” polar align scope, only RA should need
to move/be corrected. I believe that’s the basis of the “drift method”. Since
PHD2 is mucking with Dec, that must mean either my polar alignment isn’t very
good or there’s something strange with my Dec axis. I’m going to guess the
former. So I guess it’s time to learn the drift method. I was hoping to put
that off until after the AAMM next weekend. But since I kicked the leg of the
tripod putting the OTA back on, I’m going to have to do some kind of alignment
tonight if I want to test guiding. If I get that far after working through all
of the other changes I made recently.
Mike McDonald
mikemac@xxxxxxxxxxx
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