TheSkyX TPoint and Periodic Error Corrections

Two quick things, well, not quick…it’s taken a month to get to this point:

  1.  TheSkyX is software that controls the Paramount MX robotic mount in SkySlab.
  2.  Tpoint is how that software pin-points targets in the vastness of interstellar space.

There’s a lot more to it and some complex configuration and calculations that go into it, but the basics with TheSkyX are to calibrate the mount and scope, then pinpoint and all this relies on some man-made gears and belts to keep an accurate lock on a target potentially millions of light-years away.  The belts and motor gears are capable of running at an accuracy allowing less than 1/8 of a pixel movement over 4800 seconds of exposure.  Less time for exposure gives you greater accuracy.

So, two things must be done with this system, a Tpoint run and a recording of the in-built mechanical slop in the gears and belts to correct – as much as possible – the errors that can occur when wanting accurate tracking .  After a collection of 400 points in the sky, the software tells me now that the polar alignment is excellent.  Pointing accuracy could be improved slightly, but 14 arc-seconds accuracy is close enough to get me pretty much in the center of a CCD chip without needing to move about at all.  Here’s what the Tpoint accuracy looks like as reported by TheSkyX.


After completing a this, I tried an experiment with the periodic error correction (PEC) – which is what tries to account for the mechanical slop in the gears and belt on the mount.  This is what the PEC curve looked like prior to the maintenance performed in this post.


You might not be able to see – but the error was of the order of 3 arc-seconds (about 1.5 up and down).  Here’s what the raw data from the periodic error after maintenance looks like.


Then from this a fit curve is generated.


And from that a periodic error curve is applied to the Paramount MX.


Upside down?  Weeeell ok, guess that’s how it’s meant to work.  You might be able to see that the error is pretty much the same as before…wonderful.  It probably is though, because after the new curve is applied the tracking was pretty much as it was before.


This might be improved by using something like PEMPro, however that’s going to take a bit of time to understand and apply.  Meanwhile, SkySlab is ready to delve into the kinds of photos a 12″ RC will offer.

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