ISS: Visual Telescopic Observation – August 28/29, 2012

Digital Illustrations of the International Space Station – August 28/29, 2012 – 0225 UT

Observation Notes:

I’ve had fun grabbing photographs of the International Space Station through the telescope, but until recently, I hadn’t managed any visual observations. This week I got down to business during a series of favorable passes over the western US. The ISS is huge–over 100 meters wide, which means on a close approach of around 400 km, it grows up to 50 arcseconds in size–that’s as large as Jupiter at opposition. The catch is that it’s also traveling at over 27,000 km/hr (17,000+ mph). So it’s slippery!

A number of other observers have taken up the challenge and had success in picking out structures on the station. See for example, this discussion at Cloudy Nights: ISS Magnification and Viewing. So, for the past several nights, I’ve set up the 8-inch Dob and given it a shot myself.

The first night, I used a 25 mm Plossl with a magnification of 48X. I was able to sight on the ISS, and then lead and/or follow it across the sky. With the low magnification and a fairly low pass, I was able to make out two coppery solar panel arrays on each side of the bright white blob of the modules in the center as it bobbed and weaved it’s way through the eyepiece with each nudge. It’s awesome to actually see structures on this amazing piece of technology as it peels a blistering trail across the sky.

On the following nights, as some of the passes got better, I moved up to the Pentax XW10 eyepiece for a magnification of 120X. That made a huge difference. The Pentax has a nice wide field of 35 arcminutes and so there’s still some decent leeway to catch the ISS in the view. With practice, it gets a bit easier to anticipate it and track with it. In fact, when the sky is dark, the bright glow of the station actually helped me re-acquire it when it drifted out of the view–just look for which side of the eyepiece has some glow emanating from it and head that direction to land back on it. One thing I realized during this process was how out of condition my azimuth bearings were. Stiction was horrible and the jumpiness from nudge to nudge was obnoxious at such a breakneck speed. So I took the rocker box apart, cleaned things up really well, and got much smoother motions out of it.

Finally on the 28th, the ISS had a very favorable approach, culminating at 75°, and I got my best view so far. The solar panels on each side appeared bifurcated lengthwise, and the coppery reflection appeared to emanate from the edges of the panels while the centers were darker. The center modules were initially pointed off to one side prior to culmination, while the struts leading to the solar panels were brighter than I had noticed before–possibly the brilliant radiators showing up. Around culmination, it was a ridiculous mess trying to keep up with it, and I was able to get back on track as it started to recede. At this point, the central structures were now symmetrically balanced on either side of the struts. As it receded further, it built up a brilliant farewell flare before dwindling away.

During each observation, I had been working on sketches by taping post-it notes to the scope and drawing what I saw in quick bursts, and making refinements immediately afterward. On this latest observation, I changed tactics and made a voice recording as I tracked it, so I could describe the key points. This turned out to be incredibly helpful for keeping my eye and hands on the observation and tracking while racking up a stream of info. As soon as I finished, I went inside, replayed the recording and worked up my series of pencil sketches and notes, and then set up the digital version above.

So there you have it! All I can say is give it a try sometime. It’s a unique thing to be able to see with your own eyes.

See also these ISS sketches:

Subject International Space Station
Max. Elevation 75°
Min. Distance 447 km
Magnitude -3.2
Date/Time August 28/29, 2012 – 7:22-7:29 PM MST (0222-0229 UT)
Observing Loc. Flagstaff, AZ – Home
Instrument Orion SkyQuest XT8 Newtonian (203 mm dia./1200 mm F/L)
Eyepieces/Mag. Pentax XW10 (120X)
Conditions Clear, calm
Seeing 5/10 Pickering
Transparency Civil Twilight