Cassiopeia Observatory

ISS-Moon Transit

Posted: 20 December 2012

The observatory was opened Thursday, 20 December 2012, at 1257 MST, 66°F, for the International Space Station (ISS) transit of the moon. CalSky had provided these prediction graphics:

It wouldn't be much of a transit but I wanted to try to image it. The sky was partly cloudy with cirrus clouds and there was a wind blowing. After powering on the 8" LX200-ACF and mounting the D7000 DSLR at prime focus + visual back + 2X Barlow Lens, I added the Orion solar filter and did some focus tests on the sun. I did this as the moon had not yet risen over the hill to the east and with the clouds, I didn't know that I would even get a chance to focus on the moon prior to the transit. The sun was visible through some thin cirrus clouds and I was able to get a reasonably good focus using sunspots, 1/1250sec, ISO 5000:

At 1320 MST, the moon had appeared over the hill to the east and was clear of the clouds. I slewed to it to check the focus, but by 1325 MST, clouds had covered the moon. Even when the moon was visible through the thin cirrus clouds, focusing was difficult. At 1334 MST, I was able to get this test image of the moon, 1/1250sec, ISO 5000:

I figured this was the best focus I would be able to get. Locked the telescope focus. All was ready for the ISS-moon transit.

All that is except for the clouds. This iPhone photo shows the sky and moon and was taken at 1341 MST:

I began the HD video recording, 1/1250sec, ISO 5000, at 1353 MST, two minutes before the scheduled transit. The recording was ended at 1356 MST. During this period, the moon was in and out of the cirrus clouds.

So, did I capture the ISS against the moon? I reviewed the video on the computer and I got it! Not great due to the clouds but the transit was captured.

Here are three frames from the less than 1 second transit video, with arrows showing the ISS:

Here is the video (full speed, not sped up or slowed down) showing the ISS transiting the moon:

You may have to view the video several times to catch the ISS crossing the bottom of the frame.

For those using Firefox and can not get the video above to load, or if you want to view the full-size HD video, I have made it available here:

Comments are welcome; use the Comments section below, or you can Email Me. Thanks.