The primary returns

No, nothing to do with politics or voting, but our primary mirror is back at UKIRT with a beautiful new coating. Some of you may have read my post about our primary mirror being removed and taken to the CFHT for realuminising. Well, it was returned on Thursday after going through the process and I can't say how happy we are with the job the CFHT did. The coating is wonderful and our measurements showed that the quality is literally as good as gold at 3.3 microns, which is about the best you could get.

No pretty pictures I'm afraid, just some snapshots of the day we got our mirror back, and I apologise for the odd colours from the CFHT clean room.

UKIRT's primary mirror emerges from the vacuum chamber where it had been coated with a few hunderd Angstroms of aluminium (and I'm going to use the American word aluminum from now on!).

This infrared scatterometer is what we used to confirm the quality of the new coating. Unfortunately it's rather unstable and as usual when scientists and engineers get together all sorts of theories, solutions and experiments were discussed, but finally we agreed that the mirror surface was giving us the same result as if it had been coated in gold.

Erik, one of our engineers, is pretty proud of the result. He's been working here almost as long as I have by the way! The odd looking striations on the mirror had me panicing at first when I saw this picture, but they're simply reflections from the lab's wall. At least we know the mirror is reflecting stuff, which, after all, is what it's supposed to do!

The mirror is very gently lifted from its support in preparation for its transport to UKIRT. I had asked our chief engineer beforehand if I needed to wear a hard hat while I visited the CFHT and he said that for this part of the work I should wear one. He then pointed out it'd probably be no use other than to help identify me after an accident. Now I know what he meant! This is several tons of glass being lifted.

Finally, after a few hours, the primary is slowly lowered onto the truck. Everyone here is being extraordinarily careful because we can't risk any damage. We don't have a spare primary.

Off it goes back to its home at UKIRT accompanied by our own security detail!

Convoy!

It's only a few hundred yards between the CFHT and UKIRT but you have to remember it's a massive piece of delicate glass being transported on a large truck - you can't do this quickly. We also had to block the road for a short time to make sure some of the more enthusiastic tourists on the summit didn't hinder the operation and for the most part they didn't!

The primary is now back in UKIRT's dome and we're planning a quick check of everything on Wednesday night which I'll be doing - we have to find those bits and pieces that everyone finds after putting something back together and wonders where this bit went.

After that it's back on sky Thursday night and I have the privilege of getting everything working again. I'm looking forward to it because that's the one job I know I'm good at.