Report of the
meeting held on
Last
updated
The third
section meeting, hosted by Newbury Astronomical Society,
was held on
Attendees
The
presentations, in PDF format, can be accessed by following the links
highlighted in bold below. Other relevant links are also highlighted in regular
font.
The Section
Director,
Speakers
Back row, left to right:
Front
row, left to right:
The
first speaker was
Edgeworth-Kuiper Belt Objects (EKBO’s) orbit beyond
Past surveys of TNOs are probably a poor representation of the
true distribution of EKBO inclinations because most were found in surveys
centred on the ecliptic. Such surveys
were biased towards finding low inclination objects which spend the majority of
their orbit close to the ecliptic.
A 0.9 metre telescope at Kingsland Observatory,
The survey also includes a search for a hypothetical ninth
planet beyond the EKB as a follow-up survey of some 'suspected planets'. The follow-up survey this year will attempt
to detect whether or not this planet exists based on the targets located by
prior research.
The last of the morning’s speakers was Dr Alan Harris, Senior Research Scientist at the Space
Science Institute in
Only slightly more than a decade after the discovery of the
first asteroid binary, more than 100 of them have been discovered by a variety
of techniques. Over the same period of time,
the number of asteroid with known rotation properties has more than
tripled. This has been largely due to
the advent of robotic CCD telescope systems, many of them owned by amateur
astronomers. Not only have these
observers taken the lead in lightcurve observing, they are now the leading mode
of discovery of binary asteroids, through lightcurve observations of
eclipses. This explosion in data has
gone hand in hand with theoretical work on radiation pressure alteration of
asteroid spins (YORP effect) to revolutionize our picture of the physical state
and evolution of the small bodies in the solar system.
The "Photometric
Survey for Asynchronous Binary Asteroids" is a collaborative
effort between professional and amateur observers, led by Petr Pravec of Ondrejov Observatory,
pole/orbit orientations of binaries and look for eclipse events
at other geometries than previously observed.
Further details, along with a listing of participating observers, can be
found at http://www.asu.cas.cz/~asteroid/binastphotsurvey.htm.
An excellent buffet lunch was provided by
The
afternoon sessions opened with
The
presentation covered the basic techniques of observing, timing, and recording
planetary, (+dwarf planetary!), asteroid, and planetary satellite
occultations. The "New Order"
in equipment and techniques available to the modern well-equipped amateur were
then discussed. These included telescopes, 'impersonal' timing and recording
equipment, accurate time sources, site coordinates, predictions, reduction
software, mobile observing, and collaboration in European and worldwide pro-am
networks via the internet.
The next
speaker on ‘Aspects of
Asteroid Photometry: Observing campaigns’ was BAA
President and Assistant Director (Photometry), Dr
Amateurs
equipped with CCD cameras can help push back the scientific frontiers in
asteroid research. To do this
effectively requires them to unite with others or, at the very least,
coordinate their observations with those of others eg: Brain Warner’s Collaborative
Asteroid Lightcurve Link (CALL), Raoul Behrend’s CdR-CdL
and Petr Pravec’s Binary Asteroid Group. This talk recalled how observing campaigns have
developed over the years and set out the various options now open to interested
observers. BAA activities were
highlighted and future observing campaigns mooted based on the data in the 2007
and 2008 BAA Handbooks.
Before the
mid-afternoon break Dr.
The
magnitude scale was developed by Ptolemy – a difference of 5 magnitudes being
equal to a change in brightness by a factor of 100. Originally 6 orders of
magnitude were defined whereas today the range is approximately 55 from the Sun
(-26.7) to the faintest objects detected by the Hubble Space Telescope (approximately
29). Amateur astronomers need to be able to calibrate their photometry down to
at least magnitude 18 and preferably fainter. Badly calibrated data is useless
and misleading if published. The aim should be to quote a magnitude in a known
system or one that can be converted to same.
Mark
emphasized the Photometrist’s Commandments – be systematic and understand your
limitations. The limit to accuracy, no matter how well you calibrate and how
good the seeing conditions are is about 3% or 0.03 magnitudes. Even if the
error is known to be large it should be quoted. A good signal to noise ratio
(SNR) is vital for accurate measurement of magnitude
Since 1990
he has worked with a group of astronomers in
His second
talk, after the break, was ‘The
asteroid impact risk reviewed: has it been greatly overestimated ?’
The potential threat is indicated by the 138 asteroids on the JPL Current Impact Risk List of which only 5 have been observed recently. The combined impact probability of all these asteroids gives a 1% chance of an asteroid hitting the Earth in the next century. However 70% of that probability can be assigned to just 2 objects both of which are small and may not penetrate the atmosphere to reach the Earth’s surface.
The last
speaker of the day was Peter Birtwhistle, Assistant Director (Astrometry) described the ‘Tracking
of Near Earth Objects’.
After
describing his observatory Peter explained how he used the Minor
Planet Center’s NEO Conformation page (MPC NEOCP) to follow up
recent discoveries. He explained that newly discovered asteroids can be
difficult to find or lost if they are Very Fast Moving Objects (VFMO’s) or
there is a delay in their appearance in the NEOCP. As do many amateurs Peter
uses Astrometrica. This enables faint objects to be detected by stacking
multiple images and outputs data in the format required by the MPC. His
technique for capturing images of VFMO’s is to take many short exposures of a number
of fields spanning the predicted position of the object. Timing is all
important for accurate astrometry particularly of VFMO’s. Synchronising the
PC’s clock using Dimension 4 Freeware
is Peter’s preferred method but he noted that GPS receivers are also suitable
timekeepers. He closed his presentation by mentioning that distant artificial
satellites make good targets for practicing VFMO imaging.
Director