Thursday, 30 June 2011

Ice in the works

After spending two-and-a-half years somewhere in UKIRT's attic the wavefront sensor was brought out today and installed on the telescope. This is a relatively simple instrument that allows one to align the telescope and take out-of-focus images of the primary mirror which helps us to see any optical aberrations caused by the primary and secondary mirrors and correct them. The good news is everything worked first time, all the mechanisms moved correctly and I could take data. The bad news is that during the long hiatus moisture got into the CCD housing and since the detector is electronically cooled below the freezing point of water, ice formed very close to the CCD. You can tell it's close since the image shows ice crystals in focus (if they had been anywhere else, they would be out of focus and the image would just be one big blur). The good news again is that the ice is in the detector housing, it's a relatively easy problem to fix. The housing is already being baked in an oven to remove the water (yes, an oven, but not quite the same as you have in your kitchen!) .

Tomorrow the instrument will be put back together and I'll try again. I did try to take some images to see if I could at least align the secondary mirror, but it was all too blurry so will wait until tomorrow.

This is an image, taken through the ice, of the primary mirror covers. If the ice wasn't there you'd see marking indicating north, south, east and west and some markers to help me align the secondary (the lighted circle in the middle). The four black lines are the secondary vanes, the structure that holds the secondary mirror at the top of the telescope structure and the things that give rise to diffraction spikes you see in almost all astronomical images of bright stars.

In the meantime, my good friend Paul Hirst appeared on TV today, he often comments on this blog so you may have seen his contributions in the past plus I have been known to show a photo or two of his! I think he did a great job in the interview, especially as he didn't forget his old stomping ground, UKIRT.

You can see the interview via this KITV link.

It was nice to get back to the summit again although I have to admit I felt the altitude, it's been a long time since I was last up there. Back again tomorrow to see if the wavefront sensor works and then again on Sunday to begin a long shift back on the mountain. I'm looking forward to it and will try and post a few photos!


Anonymous said...

The ice looks like something one would see in a kaleidoscope tube. Pretty designs, I think.

Anonymous said...

Thanks for the video interview with Paul Hirst. Like his accent, lol.

Paul Hirst said...

Thanks Tom! Just taking a break from celebrity high life to catch up with the blogosphere! :-)

Yorkshire born, Yorkshire bred, 'n all that. :-)

I'm curious - is that the Cass M2 / do you have a cass instrument on / have you modified the wfs to work with the wfcam M2??? :-)

Tom said...

Paul, we're in Cass mode for Celeste, a visiting instrument. UFTI and the WFS are on as well but no place for CGS4 or UIST.