Old 30-09-2014, 01:48 AM
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LewisM is offline
Join Date: Aug 2012
Location: Somewhere in the cosmos...
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RMS and a GPD2

Have been imaging all night tonight (YAY, what a change!) and in between the 10 minute subs, I have been fiddling with PHD graphs etc.

My average RMS for a 10 minute sub is 0.07. RA is essentially flat, but Dec is making a LONG wavelength sinusoidal wave, which is causing this RMS I presume. Polar alignment was sub-minute for alt nd az, and LOW seconds at that, so the PA is VERY close.

Would this bring it down to Dec backlash? I have the Dec balanced camera heavy. I notice a small side-to-side movement of the Dec head when the mount is shut down - should I tighten this until it JUST binds ever so slightly WITHOUT causing too much strain on the dec motor?

It guided for 3 hours on one target without ever moving off centroid (variations in seeing only)
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