[AANC Contacts] Asteroid HERCULINA Occultation Wednesday morning

[Rick Baldridge]

For advanced amateurs, especially those with video equipment, the asteroid
(532) Herculina occults a 11.6 magnitude star in Gemini on the morning of
Wednesday, Sept 15th at 4:18am.  The southern edge of the 250km-wide path is
right over the southern Bay Area.  San Jose might be just outside the path,
but northward observers will almost certainly be in the asteroid's shadow
for up to 7.5 seconds (if the event is central for your location).

Detailed charts and track maps can be seen at:
http://asteroidoccultation.com/2004_09/0915_532_1912.htm

Herculina was my first attempt at asteroid occultations back on July 7th,
1978 at Foothill College Observatory. It was only the 7th asteroid
occultation ever observed, (now there are over 350 events timed).   I had a
miss, but during that occultation, a possible moon of Herculina was
indicated by one observer and there's a possibility that this occultation
will confirm that for observers even FAR from the path.

Predictions were somewhat crude in those days, and I spent the next 25 years
making occasional attempts until my first success on asteroid (139) Juewa on
April 20, 2002 at Oakridge Observatory with an intensified video camera.  As
luck would have it, PAS President Bill Sorrells and VP William Phelps saw
the same event from Foothill College and were able to report timings as
well, enabling a diameter of 177.9km to be determined for the asteroid.
Ever since the extremely accurate Hipparcos star catalog came out,
asteroidal occultation prediction accuracy is to the point where track
accuracy is as good as a fraction of an asteroid's diameter (for larger
asteroids).

Most asteroidal occultations are fairly easy to observe visually through a
telescope if the asteroid is fainter than the star and the drop in combined
light is greater than 1.2 magnitude or so.  Unfortunately for the upcoming
event, the drop is only 0.6 magnitude, meaning video or photometric
equipment is needed to reliably make a timing.

If you really want to make a contribution to the science of astronomy, and
perhaps discover a new "moon" of the solar system, give this occultation a
try.  Feel free to call me if you need help.


Rick Baldridge
Campbell, CA
(408) 374-4573