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Planets present a limitless opportunity and challenge for observers.
Any clear night features some minor planets favorably placed for
observation, and the number observable approximately doubles for each
30% increase in aperture size. With
smaller telescopes asteroids are entirely star like in appearance.
Simply identifying them and tracking their motion across the star
background hones good observing skills even for beginners.
The late Dr. J. U. Gunter wrote:
"Minor planet observing welds the observer, his telescope,
and his charts into an efficiently functioning unit." It
is the goal of the Minor Planets Section to support all aspects of minor
planet study and publish the findings in the quarterly Minor Planet
Bulletin. Several
categories of useful minor planet research are in progress by members of
the Minor Planets Section. Astrometric measures are nowadays performed
with CCD cameras and automated measuring software with the results
forwarded directly to the Minor Planet Center of the Smithsonian
Astrophysical Observatory. Members
able to reach magnitude 17 and fainter with their equipment are
discovering new minor planets, and with their discoveries accorded the
right to recommend names. Some
of the most valuable research being performed by the Minor Planets
Section is CCD photometry to obtain rotational lightcurves.
The best pioneering work is currently being done on minor planets
in the magnitude range 13
to 15. It is strongly
recommended that a series of lightcurves of the same minor planet be
continued over an interval of several weeks or longer.
This extended observation interval is needed to derive accurate
rotational parameters. For
an elongated minor planet rotating about its shortest axis the typical
lightcurve contains two maxima and minima per rotation, and the interval
between these determines the rotation period.
The difference between maximum and minimum light is an indicator
of the amount of asymmetry between the axes.
In some cases one or three lightcurve maxima per rotation
resulting from a more complex shape or surface albedo variations
provides challenges to interpretation and additional lightcurves become
especially desired. When
the rotation period is a simple fraction of the Earth's, observation at
a single observatory cannot cover the complete lightcurve and
fundamental rotation data become ambiguous.
For these cases the Minor Planets Section coordinates observers
at widely varying longitudes to observe the same minor planet and
thereby obtain among them the complete lightcurve. Among
the many thousands of catalogued minor planets there are inevitable
errors in the published magnitudes.
Rotation and aspect variations complicate the determination of a
single "average" value, but even beyond these some large
discrepancies are being found. This
is a study to which visual as well as CCD observers are making important
contributions. The Minor Planet Section's Magnitude Alert Project (MAP)
serves as a center for e-mail collection and rapid dissemination of
magnitude discrepancies, which are checked by other cooperating
observers. In the past few years Alerts have been sent for more than a
hundred individual minor planets and definitive improvements have been
obtained for many of these. For
any minor planet new observations are always welcome.
Even for the brighter, well-studied minor planets new
observations further improve the accuracy of orbital and rotational
parameters. Previously
unstudied or only briefly studied objects beckon without limit.
People interested in joining the fellowship of minor planet
observers are welcomed to contact the Minor Planets Section Coordinator.
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