An Upcoming Asteroid Occultation by Rick McWatters
A convieniently timed asteroid occultation may be visible to lucky observers in the Great Lakes region on the Sunday evening of August 26. A 9.5 magnitude star in Ophiuchus and 12th magnitude asteroid 85 Io are the protagonists. For a finder chart, see page 77 of the August Sky and Telescope.

This is the kind of event you can observe from your own backyard if you have a reasonable view of low declinations (-8 ). Besides a telescope, the equipment needed is a tape recorder and time signal radio or short wave tuned to WWV (2.5, 5.0, 10.0, 15.0, 20.0 MHz) or CHU (3.330 or 7.335, 14.670 MHz). WWV is usually the strongest signal. Find the star field a few nights earlier so you are not frantically searching 5 minutes before the event! Begin a serious watch about 10 minutes ahead of the predicted time and make sure you are comfortable (sitting), because you don't want to look away and miss the onset of dimming. Continue watching until at least 10 minutes after the predicted time. Some asteroids do have their own satellites so you may witness a "special" event.

Depending upon the sky conditions and size of scope you may perceive spurious dimmings which are really atmospheric in nature. You should say so on tape even if you are not sure. Think out loud so these notes can be heard on the tape. Make sure the time signals are clearly picked up on the tape. The actual dimming and later brightning are quick, but not instantaneous. Also check a few days ahead of time that your time signal source is working. (It has occured to a group of us observing a grazing lunar occultation that 3 separate time signal radios did not work in the field !!! )

Accurate negative results are just as important in these events because someone near you may see something and your results will help determine the size and shape of the asteroid shadow as it skims the earth's surface. If you do setup to observe and send me your results, I need to know your observing location latitude and longitude and height above sea level. (This we can figure out from topographical maps which Andreas has.) The actual event timings need to be accurate to within a second or better (the best way of getting this is by the radio time signals, but you can get them over the telephone. If this done you should record several minutes before and immediately after observing WITHOUT STOPPING THE TAPE RECORDER)

The predicted time and area are usually updated a few days prior to the event, so any interested observers should contact me on Saturday or Sunday (August 20 or 21) for last minute revisions.

Good luck everyone!

North York Astronomical Association Resources