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Crater Gassendi, ISS, Io Transit

Posted: 5 January 2012

I opened the observatory Wednesday, 4 January 2012, at 1805 MST, 63°F. The sky was clear but there was a strong breeze blowing. At 1809 MST, viewed Venus, 77X. The gibbous phase was distinct. Then slewed the 8" telescope to Jupiter. The four Galilean Moons were visible at 77X. Io would begin a transit at 1950 MST. A low pass of the International Space Station (ISS) would begin at 1902 MST.

I then slewed to the moon and viewed it at 77X, 206X, and then 133X. Seeing was not very good again this night. I selected the Crater Gassendi for high magnification imaging. Next, in preparation for the upcoming ISS pass, I updated the ISS TLE (from Heavens-Above) in the AutoStar II. Once that was done, I switched to the visual back on the telescope and mounted the D7000 DSLR at prime focus. This is a 1/800sec, ISO 400, exposure:


This is the Crater Gassendi, "Hat Trick", ISO 640, eyepiece projection (222X), cropped from the original full-frame image:


I wish the seeing had been better, but there are still some good details visible in the image.

I switched back to the diagonal and began setting up for the ISS pass. I mounted the D7000 DSLR at prime focus + 3X TeleXtender, focused using the moon, locked the focus, and checked the finderscope alignment. I then waited for the pass to begin. I am still refining the exposure settings for this higher magnification and set it to 1/1000sec, ISO 2000, for this pass. Unlike the previous night's pass, this pass had fairly good tracking from the AutoStar. However, it was a low pass and so distance and atmospheric distortion impacted the image captured during the HD video recording. I recorded the pass for 6 minutes, 42 seconds. A few frames had a recognizable image. Here is the ISS, as captured in two highly cropped video frames:

photo photo

These images barely show the gold solar arrays. Certainly not my best images of the ISS, as seen on my Satellites Photo Album. But I will keep refining the exposure for prime focus + 3X TeleXtender.

At 1910, I removed the camera from the telescope and slewed to Jupiter. Seeing was still not good and did not allow 364X. I switched to 206X + moon filter, which allowed a better view. Io was approaching Jupiter's disk.

At 1917 MST, slewed back to the moon and did a tour of the terminator and limb at 206X + moon filter. Some nice views.

Then at 1928 MST, I went back to Jupiter for the upcoming Io transit start. I started observing at 206X + moon filter, but switched to 267X + moon filter, which provided a little higher magnification with a tolerable view, given the poor seeing. At 1948 MST, just two minutes before the Io transit would start, seeing got a whole lot worse. I thought the change might have been due to a jet contrail, but nothing was visible near Jupiter. At 1951 MST, one minute after the start of the transit, I switched back to 206X + moon filter. I could just see Io in front of the South Equatorial Belt. At 2000 MST, I had to switch to 133X + moon filter due to the deteriorating seeing. I briefly saw Io and then it disappeared as it moved away from the "limb darkened" area of Jupiter's disk.

Since the seeing was so bad and since the previous night in the observatory was so long (over 7 hours), I decided to close up for the night.

Closed the observatory at 2015 MST, 56°F.


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Copyright ©2012 Michael L. Weasner /