[g__day (Matthew)]

This is something strange I experienced. I am trying to get my polar alignment to better than an arc minute or two of the SCP (and I'd say its very close).

So I power on an do a 1 star align on Achernar - its dead centre on the Canon Camera's central finder dot. I move off the star a degree and issue a goto Achernar - and it lands dead centre on the star again.

After that I check the hand controller time - its right to the second - so I don't touch the hand controller for the next two hours...

Now I remotely take 120 shots of 3 second duration - one minute apart and look at the drift. There is no DEC drift but the mount (or SCT's mirror) make it appear that things are running slightly fast in RA. The drift on my images from beginning to the end shot over two hours is 9mm on my images (whereas the diameter of the full Moon is 186mm) - So that tells me the mount is running 1.5 arc minutes fast every two hours - around 45 arc seconds and hour say.

But out of curiosity I look into the Camera and issue another Goto Achernar - and expect nothing to happen - but no - the gears engage and the star moves back half the distances say 45 arc seconds - so its now only 45 ac seconds of the Camera's central finder spot!

How can that happen? The SkySensor2000-PC says its tracking Achernar - no adjustments are made - then two hours later (its risen from say 40 degrees elevation to 70 - so no Meridian flip) and when I re-issue the goto it moves back!

Love to know what I am experience there!