Monday, May 17, 2010

Kitt Peak Star-B-Que!

This last Saturday was the Tucson Amateur Astronomy Association (TAAA) Spring edition of the Kitt Peak Star-B-Que. The idea is simple - club members and their guests are welcome to meet up at the Kitt Peak National Observatory picnic area, enjoy a pot luck cookout, then stay far into the night for observing. I remember back in the '90s when we were first allowed to stay up on the grounds after hours - it was a pretty big deal. The chance to be on the mountain, over 6400 feet elevation, flush toilets, paved road to the site, and the excellent skies is a great combination! Back in the "Olden Days" when we were first allowed up there, we were limited to 20 people, but the limit has slowly been raised to I think 70 now, but we are rarely close to filling all the spots these days. At left is a stereo pair of the view towards the mountaintop with one of the 82 foot (25 meter) antennae of the VLBA Telescope in the foreground. Go to my first 3-D post for hints on seeing the 3-D image. As I setup the telescope, Melinda cooked burgers for us and friends Donna and Roger who joined us for the night. We brought a double batch of brownies that did not survive the night!

This time, as is often the case, TAAA member Claude Plymate, who works at the National Solar Observatory, offered a tour of the McMath-Pierce Solar Telescope after the cookout, and the 30 or so who preregistered got to observe the sunset through the second largest solar telescope in the world! Just superseded by a slightly larger solar telescope a year or two ago, the 63 inches (1.6 meter) diameter mirror forms an image of the sun about 30 inches (80cm) diameter. The key to not catching things in the lab on fire is that the focal length of the mirror is so long (285 feet, or 87 meters) that the light is concentrated only about 4 times that of unfocused sunlight, but the large image scale allows study of small features on the solar disk.

There were a score of interesting effects visible in such a large solar image, particularly as the sun neared the horizon. Looking through the atmosphere at very low angles, the Earth's atmosphere acts like a thin prism, so edges of the sun display color effects. The upper edge of the sun shows a blue-green edge that was quite striking as shown here. This effect is occasionally demonstrated as the "Green Flash", sometimes visible to the naked eye at sunset. We saw a number of jet planes as the sun neared the horizon - likely passenger planes in the busy corridor of western California. The planes are far enough they take 10 seconds or more to cross the half degree disk of the sun. We did see a mystery, though - there was a spot that took a full couple minutes to cross the sun! Claude claims not to have ever seen anything like it and did not know what it was. It seemed pretty featureless, small and perhaps round. My theory is that it was a weather balloon, again, at some distance, that slowly drifted across the sun's disk.

Before we knew it, the horizon came into view, seen in silhouette against the disk, complete with little saguaro cacti a couple millimeters high on distant mountainous horizons likely a hundred miles away. And then the sun was gone, and we left the observing room and telescope into the darkening twilight.

We all hustled down the mile and a half to the picnic area to finish our telescope setup for the evening. A skinny crescent moon shared the western sky not far from the brilliant planet Venus. This time of year we are also blessed with views of Mars and Saturn all high in the sky, so 4 of the 6 visible planets were readily visible (counting Earth, of course!). Only Jupiter and Mercury were not visible in the early evening.

We had another treat visible in the early evening sky. While the International Space Station had made a poor appearance very low in the north, the Hubble Space Telescope made a fine pass very high in the southern sky. The photo here shows the horizontal streak of HST between Saturn at top center, Corvus at lower center, and Spica at left center. And at the exact time HST was passing by, another bright tumbling satellite crossed the HST apparent path 10 seconds or so before. If you click to load the full size image, you can see the variable brightness of the out-of-control satellite.

It was a spectacular night! The seeing was a little soft early, providing so-so views of Saturn at high power, but the sky was quite clear and we took advantage of the Spring galaxy-filled sky to observe a few friends I'd not seen in a while. I also took the opportunity to hunt down some bright comets - I mentioned C/2009 K5 McNaught in last night's post, surprisingly bright just 5 degrees south of Polaris. Much harder to find was 81P Wild 2, hiding among the disguising fuzzy galaxies of Virgo. I'm glad I took a break from the comet searches to check out Saturn again - the seeing had improved markedly and it looked fantastic! One of the moon's motion was easily detected from earlier in the evening as it moved inward past the tip of the rings, and the rings themselves, as well as their shadow cast on the disk of the planet stood out in sharp relief. it was quite fantastic...

I took occasional observing breaks to take some images that caught my eye. The summer triangle was rising over the mountaintop and a very busy radio telescope. I was taking 2 minute exposures which was just about the maximum length of time the dish spent sitting on one object before moving across the sky to another object. It was tough to catch it from blurring! The Summer Triangle consists of Vega at top center, Deneb at left center, and Altair just clearing the mountain at right. The cloudy glow of the Summer Milky Way is just winning the battle of being drowned out by the glow of city lights of Tucson directly behind the mountaintop and Observatory. The domes visible against the sky are the 4-meter Telescope at left, Steward Observatory's 2.3 meter just to it's right, and to the right of the radio dish is the 3.5 meter WIYN Telescope.

Before I knew it it was nearly Midnight and I had a few tuckered observers ready to call it an evening. Surprisingly, given the quality of the night, there were only 2 cars left when we pulled out, but many people might have left early to go down the unfamiliar road. While people were packing up, I took a stroll with a tripod-mounted camera to catch the rising Milky Way and Scorpius. Here Jim O'Connor is packing up his scope under the rising dark clouds of the Scorpion.

With the pleasant temps and low-key spectacular observing, it really makes me wish we could get out more often under such amazing skies. With the summer Milky Way getting higher, and Summer heat approaching, it is time to head for the high country soon. Grand Canyon is only 3 weeks away!


Astroweis said...

Hi Dean,

we had a great evening and a greater night on Kitt Peak.
You really are blessed with your skies in Arizona.
It was the first time for me to see the Milky Way in Sagittarius glowing so brightly that you could confuse it with clouds.
Thank you for your article, I enjoyed reading it.


Anthony Vodraska and Anita Gilbert said...

Reading your post almost felt like being there. I wish I had been there. The description of your viewing at the solar observatory was vivid and captivating. Many thanks for sharing these moments.