I was fortunate to have one good night to put the MIT PICO camera through its paces on the 60″ (1.5m) Richey-Cretein telescope at SPM Observatory. I am grateful to be guided by fellow astronomer Raul Michel, who not only operated the telescope but provided expert tutelage through the data gathering and reduction process. Here’s a link to the data we used to find (762)Pulcova.

Here’s how the night went; first we looked for our primary target – KBO 55636, ?which was what MIT was paying all that money to capture on October 9th. Though we didn’t image (take a digital picture) of the asteroid itself because it’s really dim, the folks at MIT and elsewhere have crunched lots of data to predict with some certainty where the asteroid will be. So we photographed the star that will be either very close to, or will be occulted (eclipsed) by the asteroid. Here is an image we took of that star. Note that we inverted the black and white because it’s easier to make out the stars.

So far, we proved that (1) we can find the star they need us to photograph, the telescope aiming system is very accurate, and (2) that PICO works, because we were able to capture the image, and (3) that we had a little mix-up in our time-synchronization?procedure that could be corrected before the ‘real’ event the next evening.

Now that we knew that everything worked, and had a good idea how to set the camera, we moved onto the target that the?International Occultation Timing Association (IOTA) asked us to gather data on, (762) Pulcova/TYC 2314-01655-1. The star was predicted to be eclipsed by the asteroid Pulcova at exactly 09:38:00 UTC. UTC is a timing standard that is generally the same as Greenwich Mean Time (GMT). If you’re in Boston, then add 4 hours to your time, so noon in Boston is 16:00 UTC. We’re in western Mexico in Baja California Norte which is 7 hours behind UTC, so 09:38:00 UTC is 02:38:00 (2:38 AM) for us.

After moving to the proper coordinates, we took some images in order to focus the telescope. And then at 09:22:00 UTC we began taking a series of 1,100 images, each image exactly 1-1/2 seconds after the last. Here’s some of the results. In this picture I took every 50th frame and made a mini-movie so that you could watch the bright asteroid cover the even-brighter star as we did. ?Notice the asteroid on the right in the first frame, then watch it move and cover the star before it starts to emerge from the other side.

With untiring determination Raul Michell of UNAM reduced the data from each image to quantify the instrument magnitude (the total brightness as detected by the PICO instrument) of both the star and asteroid over time. The resulting plot clearly shows that there was a drop in magnitude (period within the red vertical lines) which, because the exact time of each image is part of the data set, lasted for about 16 seconds. Each tic mark in the X-axis represents 8.64 seconds. To state time with great precision, astronomers use a time scale called the?Heliocentric Julian Date (HJD). I think it’s just to confuse non-astronomers so they can demand more money ?Each tic mark in the Y-axis represents 0.2 magnitude. The larger the magnitude, the dimmer the object appears. And because of the time sync glitch we uncovered after the event, the times in the chart are 6 seconds later than the actual event.

Click the plot to see a larger version in a new window.