How to Catch a Transit: ISS Over Tycho

The true beauty of orbital mechanics is that since Newton's day, we have come to amass an incredible store of orbital data on thousands of interplanetary objects, and know their orbits with incredible precision. So much so, that there are now some very simple online tools that even the complete astronomical novice can use to directly observe our technology in orbit as it passes in front of either the sun or the moon. Last week I posted a great solar transit photo of the ISS, and ever since then, I’ve had a number of people first, question their credibility, and second, ask “how exactly do you catch one in progress?”

So here are some nice Lunar transit shots complete with a commentary on tools and techniques. The nice thing about Lunar transits is that all you need are some binoculars or a small telescope to enjoy them, and access to the Internet to know when they are coming up. (The solar transits warrant a little more caution due to the risk of blindness and damage to telescope optics if proper filters are not used to image the sun.)

The International Space Station's new solar arrays are clearly visible in this video image montage taken by Ed Morana a few days ago through a 10 inch Mead LX200-GPS telescope. (Original link from Space Weather.)

Here’s how he did it (from Ed's site):

The ISS was going to be at a range of only 260 miles. Thanks to the e-mail from Thomas Fly's ISS Transit Alert service, I knew in advance that I had to travel 15 miles to get to the observing site just outside Tracy, CA. After obtaining the latest orbital elements from Space-Track.org and entering them into SkyMapPro, I knew where to point my telescope. The transit would occur very near impact crater Tycho! The composite image above consists of 6 frames (12 fields) with the ISS moving right to left. Equipment used: Meade 10" F/10 LX200GPS telescope, No Focal Reducer, Watec 902H CCD Video Camera and the KIWI OSD Video Time-inserter connected to a Garmin-18 LVC GPS.

General Observing procedures:
First, theISS Transit prediction is first obtained using Thomas Fly's ISS Transit Alert Service.

Then, a few hours before the predicted transit event, download the latest ISS orbital elements from the NASA Spaceflight web site and Space-Track.org.

Then load the elements closest to the prediction time into Sky Map Pro.

Then print out a map which provides details of the transit, including Altitude & Azimuth, direction of ISS, time of transit and CCD Field of View.

Other resources: Heavens Above and Cal Sky.

Dark Skies!