Telescope mount polar alignment

The observatory having reached a point where it’s usable, the first job was polar alignment of the RA axis of the mounts. When setting up on a nightly basis I’ve always just tried to get Polaris in roughly the right place in the polar scope reticle, but now the mounts are on permanent piers I thought I should try something better.

It struck me that the easiest way to do this would be to ignore the PCs that are going to run the mounts long-term (because the display is in the warm room), fit a camera and telescope to the mount and plug them all into my laptop, allowing me to stand at the mount and adjust its position whilst looking at the laptop screen.

The first mount was one of the NEQ6s, with a Skywatcher ED80 and ASI174MM. I booted the laptop into Windows, started up Cartes du Ciel, EQMOD and PHD2. Once PHD2 had recognised the camera I spent a happy few minutes trying to find focus before realising that I’d need a fairly big extension because there just wasn’t enough backfocus. A 60mm T2 extension screwed onto the back of the drawtube and into the camera did the job nicely. I opened the alignment tool in PHD2, pointed the telescope where it needed to be (using CdC) and set about adjusting the mount according to the guide trace.

I don’t know why, but I found the whole process quite awkward. Partially I think it’s because the alt adjustment on the NEQ6 is just rubbish for UK latitudes. Not being able to see the circle shown as the target for moving the guide star because I wasn’t sufficiently close already was a pain, too. Especially when I could see only part of the circle and in fact I needed to be moving the mount in the opposite direction. Sometimes I’d think I was getting close only to find that the next test run showed the alignment as being much further away.

In the end I got to within about 5 arcminutes of the pole and decided that was as good as I could get, but I wasn’t really happy because I felt I should be able to do better.

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