Other SJAA Activities
Here are some other activities that SJAA
members participate in
in addition to our regular meetings and star parties.
Special Activities
These activities are scheduled irregularly or on short notice. They may
involve the whole club, replacing regular meetings; or may be arranged
among a few people. While regular club functions are usually on Saturday
evenings, these special activities may be during the week and at odd hours,
as circumstances dictate.
Public Star Parties
These are demonstration sessions, not for our own observing, but to bring
Astronomy to the public, and to popularize the hobby. A regular series is
held at Houge Park,
and occasionally in such places as parking lots of
department stores, wherever there are crowds of people. Planetarium
grounds have been used, especially on the yearly "Astronomy Day".
Another type of Public Star Party is held for a particular group, such as
a grade-school science class. These may be held in town at the school or
at a nearby park. The bright objects are shown and explained to the
attendees and there are lots of questions about telescopes and astronomy.
Please don't think you need to be an expert -- this is a good opportunity
for beginning astronomers, too.
Messier Marathon
This is a mountain star party, at which the specific goal is to observe
as many of the Messier
objects as possible, all in a single night. They
are held yearly in March, since at that time, all but one of the 109
objects are observable sometime during the night. Several very experienced
people have found all of the 108 that it is possible to see at that time of
year.
The "Messier Club" is made up of persons who have observed and recorded
all of the Messier objects within a two-year period. One simply signs up
for the program, then goes to work on it, at star parties or by oneself,
perhaps at home. A certificate and plaque are awarded by the Astronomical
Association of Northern California (AANC) upon completion.
(additional info from SEDS)
Lunar Grazing Occultations
As the Moon revolves about the Earth, it occults (hides) stars - in
effect, casting a shadow within which the star is hidden. Since the Moon
is quite mountainous, the edge of the shadow is actually a band a few miles
wide, within which the lunar peaks hide the star and the valleys let it
shine again! One sees the star switching off and on, perhaps several
times, before the moon has finally passed by.
By combining the results from 10-20 people set up along a road, a profile
of the lunar limb is developed - measured with an accuracy of a few hundred
feet from 240,000 miles away!
These expeditions are held a few times a year, when the combination of
star, position of moon, phase, and weekend all come together. Sites are
all over the place, wherever the limit line falls, typically 10 to 150
miles of driving.
Asteroidal Occultations
These are a variant of the lunar occultation with several differences.
The occulting body is an asteroid, far smaller than the moon, and at a far
greater distance. The position of asteroids is not very well defined, so
the prediction of the limit is very crude at first, maybe only to which
continents are likely to be involved. Then about a week before, the path
is refined to somewhat better accuracy, typically to which states will be
involved. And that's about the best that can be done. Then we get out and
try to catch it.
But the exciting thing is not only the uncertainty as to whether we'll
see it, but that there is strong evidence for the existence of satellites
around asteroids, satellites that are observable only by their shadows.
Here is the leading edge of asteroidal astronomy - and it's in the hands of
amateurs, who alone have the portable equipment to do the job.
Observing asteroidal occultations is done from sites separated by a few
tens of miles - often simply from one's home. One needs to be able to
tolerate short notice and odd hours. But the potential rewards are great -
discovery of a new member of the solar system!!
Asteroidal occultations provide the only direct way to measure the size
of the asteroids, and so to establish calibration of the indirect measures,
such as polarimetry.
Meteor Surveys
This is an effort to aid international meteor counts on high peak
showers. Dark sites are selected, and members count the meteors, direction,
magnitude, origin, and direction. The results are summed, analyzed and sent
in. Usually three sites and many observers with and without photographic
equipment are used.
Paraprofessionals: IOTA,
AAVSO
These are international organizations that co-ordinate observations in
their respective areas. The occultation timings and variable-star
observations are individual activities, and not SJAA as such.
Nevertheless, there are people active in these areas and they are available
to advise one whose interest runs to these paraprofessional activities.
Among the sciences, only in astronomy is the work of amateurs accepted by
the professional community. And though one can derive great pleasure in
the contemplation of the wonders of the night sky, there is, for a few, a
special kind of joy in being able to make a scientific contribution to
one's field of interest. The lunar grazes and asteroidal occultations,
already discussed, are among these; there are a few observers doing
variable stars who welcome newcomers to this important field.
Jim Van Nuland / Bill Arnett; last updated:
1997 Jan 29