Return to Kitt Peak

We’re halfway through our second observing run to follow up overlapping-galaxy pairs (and it is still a lot warmer than that picture from Spain looks in the last blog entry!) . Anna and I arrived yesterday at Kitt Peak National Observatory southwest of Tucson, Arizona. She got here at lunchtime, and I didn’t make it until just after sunset because of a committee meeting in town. We’re using the 3.5-meter WIYN telescope (Wisconsin-Indiana-Yale-NOAO – it takes more than a village to build an observatory!), located at Kitt Peak National Observatory. As we did last April, we’re using a camera called OPTIC, which can be temperamental in the software and networking departments but can deliver very sharp images through tracking of atmospheric image motions right on the chip during an exposure. We’ve gotten several images as sharp as 0.5 arcseconds, which is not much bigger than a single SDSS image pixel. The combination of a larger telescope and much longer exposures let us measure features that the SDSS survey images only hint at.

Last night’s startup was a bit rocky, which sometimes happens because of the complexity of the programing and network interfaces for modern telescopes. A programmer in Tucson was rewriting router software to get rid of a problem that had the telescope shutting itself down just about the time we’d be ready to take an image. So four hours after dark, we were up and watching. We finally got images of six overlapping-galaxy pairs, two of which were only found in the Zoo recently, coming from the new celestial real estate covered in the seventh SDSS data release. (Did I hear someone wondering why they should keep examining the GZ galaxies?) We’re trying to plan our session as carefully as the uncertainties of weather and equipment allow – this time we have three nights, instead of the five we had last April. The difference comes from the fact that this time of year, we see the “narrow” side of the SDSS, a region of sky in which it covered only a few fairly narrow strips, so we can do much less than half of the candidate pairs from GZ. On the other hand, a clear night in November is a lot longer than one in April; we can be on the sky and working for twelve hours if we’re careful about what filters we use in twilight. The SDSS galaxy sample has big gaps in right ascension, where we mostly see Milky Way. (Not that the stars in our galaxy are uninteresting, but I find other galaxies more my cup of tea – and so, I gather, do most Zoo readers). So after we caught one pair of galaxies at the start of the night near 270 degrees RA, we jumped almost 60 degrees to pick up a series near 0. Soon we make the next big jump across the Milky Way in Orion and Taurus and pick up the myriad objects starting around 105 degrees. Night by night we’re shadowing the Moon as it moves past this area; there were some galaxies that were just not sensible to do last night. As it moves from night to night, it fades past third quarter, so it gets easier to plan around. We got started on schedule tonight, after watching the International Space Station glide across the same view with Venus and Jupiter. The image sharpness, what astronomers call simply “the seeing”, has varied a lot as the wind changed, bringing with it changes in air temperature and turbulence. As we get time to look at our data closely, we can se some additional calibrations to be sure of. Just now we’re juggling the order of a couple of observations, looking at the next couple of galaxy pairs in a blue filter before the third-quarter moon comes up and brightens the sky. Then we’ll go back and pick them up in the I filter, so far to the red that moonlight is much dimmer.We’ll leave off for now with a couple of sample images, straight off the telescope. To compare the SDSS Explorer images, their ObjIDs are 587727222479782085 and 758883882201710832. At least one of these has the poor taste to have the dust-poor lenticular galaxy in front, instead of behind where we’d like it. On to the next one…