Cassiopeia Observatory

ISS Captured with 8" LX200-ACF and D7000 DSLR

Posted: 1 November 2012

After last night's aborted International Space Station (ISS) video recording (thanks to the US Federal Government electric company that supplies power to my location), I wanted to try for this night's pass, although the track was not as ideal for imaging. Unfortunately, clouds arrived during the early morning hours and continued past sunset. I decided to open the observatory anyway, which was done Wednesday, 31 October 2012, at 1708 MST, 85°F. I updated the ISS TLE and then slewed the 8" LX200-ACF to the star Altair, which I hoped to use as a focus star, assuming clouds didn't block it. I then noticed this visitor nearby:

At 1738 MST, Altair was visible in the 26mm eyepiece (77X). I mounted the D7000 DSLR at prime focus and did a focus test using the Bahtinov Mask. I could not see Altair in the finderscope, so was not able to check its alignment.

At 1746 MST, all was ready for the ISS pass to start. The pass would begin about 20 minutes after sunset, so the sky was still bright. And there were clouds over much of the projected long track across the sky. To complicate matters, the ISS would rise behind some trees (in a cloudy portion of the sky). I decided that I would probably have to start the telescope tracking on AOS time, not visibility.

When the pass started, I could not see the ISS so I did start the telescope tracking and HD video recording (1/2000sec, ISO 2500) based on time. I finally saw the ISS with my naked eyes about 2 minutes into the pass, high in the northern sky. I had to do a major slew of the telescope and finally caught up to the ISS as it was near the end of the pass in the eastern sky. Tracking was good once I got the ISS centered in the finderscope. As it turned out, the finderscope was still properly aligned from the previous ISS tracking session. The ISS stayed visible during this portion of the pass although thin clouds hampered the view somewhat. The ISS was captured in the video during this latter portion of the pass. Here are three views (magnified frames from the video), showing the changing perspective:

Due to the clouds, I decided to end this session. But first, I slewed back to Altair to refocus the 26mm eyepiece. Oops, the GOTO was way off. Apparently, during my major slew to center the ISS I had tried to slew past the Declination hard stop, and so messed up the AutoStar alignment. I did a new One Star alignment. Fortunately, Polaris and Vega were visible through thin clouds and I was able to complete the realignment. As normal, I PARKed the telescope.

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