Today Colin and I started levelling the Gmount. Since we are going to be operating in the azimuth axis only, it is important that we get the telescope as perfectly aligned as possible. Well, what would be ideal would be to align the telescope with the pole (like a pseudo-equatorial mount) but at the moment we are just trying to get it level with horizontal! Doug remembered that the precision spirit level (in a wooden box) that Mark used for this purpose last year was over in a building in the dark sector, so Doug, Colin and I traipsed over there first thing. We wandered in and found someone who produced a spirit level for us. It was in a brown wooden box, so it had to be the same one as last year, right? Well Doug thought so. We brought it back over to the AASTO, and calculated that one division on the scale corresponded to an angle of 8.6 arcseconds. Doug was slightly confused because the number he remembered from last year was 30 arcseconds but he did the calculation again and decided it was right. Anyway, Colin and I headed up the Gtower.

The tent is off the Gtower now, and we had chosen a windy, snowy, overcast morning to start the procedure. I can safely qualify this as the coldest I have ever been in my entire life. Which is not hard since this is the first time I've left Australia but still, it was very very cold. The basic procedure is to loosen one of the three mount points and turn a nut to lower or raise that point. We spent over an hour and a half getting it pretty much perfect in one axis (with a few trips inside to defrost - boy it was cold!), then Colin said "Ok, turn the level around." I looked at him oddly and turned it around. It wasn't level anymore! The level obviously wasn't calibrated so that the bubble sat in the middle when it was level. Grrrrr! We decided to go to lunch and ask the engineering people if they could calibrate it for us.

Lunch came and Jess Dempsey was chatting to us. We told her about our problem and she suggested that we use a different level that she had used recently which was definitely well calibrated. So Colin headed out to the dark sector again and grabbed it. When he arrived at the AASTO with a black wooden box, Doug decided that this was, in fact, the level that had been used last year. Sure enough, when we pulled it out of the box it had 30''/division written on the side. We took it up the tower and within half an hour had both axes levelled. This was just the coarse levelling though, the fun part was still to come! We tied the level to the side of the Gmount and rotated it through 360 degrees, stopping every 30 degrees to take an image of the bubble. The idea is that if the mount is level, the bubble will not move throughout the rotation. We wandered back to the station to analyse the pictures and got a nice smooth-ish curve showing us that the mount point closest to the AASTO was a few tenths of a division too low.

Since we were psyched (well I was) we headed back out after tea to see if we could improve the error (and also since we remembered that I had forgotten to re-tighten the last mount point). Unfortunately the camera gave up after a hard day's work and I didn't have the spare battery on me so we will have to keep going tomorrow! I had learnt my lesson by now though and was wearing every layer of ECW gear that I was issued. Trust me, going to the bathroom becomes quite a production with that many layers!

- Jessie