Observations on the evening of the 8th of November marked the first official observations at the Pear Tree Observatory since it passed final inspection by the city building inspector. The object being observed that night was also special. As you might have heard, that evening, asteroid 2005 YU55 passed the earth within the orbit of the moon. The asteroid is relatively large with a diameter of 400 meters. Being this close meant it was covering a lot of sky very fast; that large meant it would be quite bright.
Since I have had problems in the past finding close fast objects with TheSky6, I used the Minor Planet Ephemeris Service to generate a list of coordinates appropriate for the observatory’s location. Guest astronomer Frank Atchison and I used those coordinates to position the telescope. 2005 YU55 was moving so quickly that we missed it several times using coordinates based on the current time. We couldn’t get coordinates for ‘now’ entered in, slew the telescope and take an image before the asteroid left the field of view. Ultimately, we positioned the telescope 15 minutes ahead of the asteroid and we took exposures until it passed into and out of the FOV. All the while, we watched as clouds appeared over the tree line and headed for the part of the sky that we were pointed at.
”]This image is a stack of 3 individual exposures. One being 30 seconds, one being 10 seconds and the last 1 second. The asteroid in the 1 second image is very near the bottom, left of center and just left and below a double star. We used this set to determine that the asteroid was traveling so fast that a half-second exposure was needed to get a un-smeared image. Of course, by then we had a pretty solid cloud deck getting in the way and the next set of half-second images were useless for measuring.