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 f
rom 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
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San
Jose Astronomical Association 