Sunday, August 26, 2012

You gotta love this telescope

Last night was my first night at WIYN where I knew it was going to be good.  A few puffy clouds floating around in the afternoon, but the weather forecast was "clear".  This was the first night predicted to be clear since June.  The wind was blowing just hard enough to feel its motion through the open dome.  I always enjoy standing on the WIYN dome floor right after sunset.  You feel like you are outside and have a clear view in every direction.

I thought the seeing might be good, so I put in the i filter before I started a focus sequence.  I've been looking at a lot of out of focus images (see my vignette on vignetting) and as I stepped by 20's through the focus values, I noticed that even as the image got smaller and smaller, it kept its donut-like shape. I could see the hole in the middle, and some consistent bright spots and irregularities in the brightness. It got very small before the images turned into blobs with a central peak.  I cut my steps down to 10, and I passed through focus and came out the other side.  Then I went back and measured the FWHM values of the images.  0.42 arcseconds.  That was the best.  That was among the best seeing I've ever seen.  It stayed that good - or almost that good - all night.  I worked mostly in g (where the detectors are very sensitive), and I took frame after frame with images 0.5 to 0.6 arcseconds FWHM; a few below 0.5.  These were guided 5 minute exposures.  Guided with the telescope - not with OT shifting on the detectors. I took a bunch of frames of a field in Stripe 82. In each one, I could see little galaxies, but they were not just smudges; they had spiral arms and nuclei and, when they were interacting, I could see knots in the streamers that were flying off them.  It was almost like looking at HST images.  I've inserted images of a couple of cells, but these don't really do justice to the data.  Remember that each of these cells is about 1 arcminute across and pODI has 13 X 64 = 832 of them.

I've got more stories from this night - including one that taught me to ALWAYS check my shoes for scorpions in the morning before I put them on - but that's for another entry.


1 comment:

  1. Great stuff Todd! Hope the weather cooperates for the next few nights.