Tuesday, July 5, 2011

More Time-Lapse Movies!

Of course, one of the points of the Grand Canyon Star Party is to have fun as well as do astronomy outreach to the public, but I also had some background projects to work on. Somehow, I've gotten the urge to get into time lapse imaging, in particular with night time images. I've posted some fixed tripod shots before, and linked them on Youtube to make watching them as easy as possible. But I was after something a little new to add some pizazz!

The answer came in a little telescope mount that was passed on to me by David and Elinor Levine. The scope is a little 5" that is mostly utilized visually on an altazimuth tripod mount, so the little wedge and fork is mostly unused. I made a little mounting plate for the fork so it would hold a camera. This time of year, the Summer Milky Way rises in the SE just after dark and transits about local Midnight. By shooting with a wide angle lens, and tracking slowly along the horizon with the stars, it would stay in view for the entire length of the sequence!

The third night of the star party, I finally got the chance to try it. With Melinda holding down the public with the 14" view of Saturn, I disappeared for a while to set up the tripod, tracking fork, car battery, inverter to run the fork, and a external power supply for the camera to prevent a dying battery from ruining a long sequence. Using the Canon XSi camera and Nikon 16mm at F/2.8 during twilight, I shot a image every 45 seconds, initially only a tenth of a second long, but as it got darker, the exposures got up to 40 seconds. I kept a watch on the histogram display to keep the exposure background right during the twilight times - once it was dark, it just went for the 40 seconds. After moonrise, and as folks started putting up their scopes, I stopped and reviewed the images - looked about right! It wasn't until a couple days later in Tucson that I saw how spectacular they were! The clip posted on Youtube doesn't even have levels adjusted - straight out of the camera!

The first frame just shows the Milky Way starting to show through the twilight as hundreds of people descended on the telescope field behind the Grand Canyon's visitor center. The second shot shows it in full darkness, and an astronomer's green laser points out an object for a visitor. Note that these individual frames have been contrast adjusted, while the Youtube video has not... I was able to get another sequence our last night on Tuesday, but wasn't able to get an early start, so this one with the Milky Way forming out of the twilight is by far my favorite.

A few days later upon our return to Tucson, I wanted to try an alternative version against the domes of Kitt Peak National Observatory. I'd previously scouted out a location, and arrived just as the sun was setting. Shortly after setting up all the gear, I started again and again caught the spectacular Summer Milky Way forming out of the twilight, this time with observatory telescopes in the foreground. This particular frame also shows a few orthographic clouds forming near the peak, but they soon dissipate. This sequence went for 6 hours, again till moonrise about 2:00am. The Youtube link is here. Again, someday, I'll go through the hundreds of images and push the contrast some... Until then you will have to enjoy these versions!

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