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2010 WC9 passed about 130,000 miles from the earth on May 15. At that time it was visible only in the southern skies. The best I could do was a day earlier when it was about 650,000 miles away. Unfortunately weather that night was awful. Lots of high clouds but it was the high winds, some gusting to 90 kph according to my weather station. Normally I'd not open on such a night as the danger of flying debris is high. But with only this one night to catch the asteroid I did give it a try with strong easterly winds. The scope is steady with north or south winds but east ones over 50 kph can be a problem. By the time it hit gusts of 90 kph the scope is no longer steady.

I ran for 30 minutes taking 1 minute exposures to keep star trails short, I'd have gone longer in good weather but the risk was high and it appeared the scope was bouncing around a bit. Winds were getting stronger so I closed the observatory. It didn't dawn on me I was using an exposure, temperature and binning that I had no calibration frames for. I went to process this a few days later but with no calibration frames, I had to put it off until I could get them. Then the weather turned too warm for me to get any until the night of July 2 when the evening temp hit 16C and I could just reach the temperature needed. I didn't get as many darks as I'd have liked as the temperature went up and I had to stop. I went with what I could get for darks and made this movie.

Yes, the asteroid does move a bit in the strong winds. The high clouds add to the background. I didn't take the time to remove the many gradients the clouds caused. The mount was tracking on the asteroid's orbital elements. No guiding was attempted.

Estimates of the asteroid's size ranged from 38 to 119 meters in size. Other sources say 60 to 130 meters, another the size of the statue of Liberty and yet another the size of a football field or stadium. Even at this late date, I don't find a better size estimate. I'd have thought radio telescopes would have been tracking it and gotten this pinned down but I can't find that that happened. If anyone knows a better value let me know.

This movie is made of 30 1 minute exposures. It covers about 35 minutes of time as my camera is only USB 1.1 so slow to download a frame compared to modern USB 2 and USB 3 cameras.

14" LX200R @ f/10 L=10x1' binned 3x3, STL-11000XM, Paramount ME

Rick