Monday, December 16, 2013

ISS Transits the Sun

Earlier this week I received an email alert from (a wonderful site for the amateur astronomer!) that the International Space Station (ISS) would transit the face of the Sun as seen from my observatory at 3:29 PM today. Once before, in October of 2011, I observed an ISS transit (see this post) and it was quite a thrill.  I was hoping to do it again and this time I was equipped with a camera that would allow me to video the event.

I invited my friend Jon Shallop to accompany me on my misadventure and as the day approached the predicted ground track of the ISS had been refined and shifted about 2-3 miles to the west.  This is due to the fact the ISS is continuously dropping in its orbit (they boost it back up occasionally) and also the solar flux can affect it's orbital path.  Looking at the map this morning it appeared that the center-line of the transit would run right over the southeast corner of Himmel Park, very close to the University in mid-town at precisely 3:29:29 PM.  As the day wore on, heavy cirrus clouds built in the southern sky and as the time approached we were worried about seeing anything at all.

I had set up both a hydrogen alpha and white light telescope and given the thick clouds decided I would scrap the video plan and visually observe the transit. Fortunately, about 10 minutes before the transit the cirrus thinned and I decided to mount the camera to the HA telescope and see if I could record anything.  Sure enough, despite the thick cirrus, I was able to capture it!  The transit occurred exactly at the predicted time, indicating we were right on the center-line.  Below is a single frame from the video, processed a bit to sharpen the details.

The ISS is just above left of center in the image.  Of course, I was in a hurry and did not notice that I had the camera binning the resolution is somewhat limited...although with the very poor seeing conditions, it may have been better this way.  The uneven illumination is due to passing cloud, and for my first attempt, I am happy with the results.