Talk

A selection of interesting minor planet occultation results observed from Australia and New Zealand during 2012 is presented.

The Great Storm started as a small white spot Dec 8th 2010, By mid January 2011 the storm had dredged up so much material that it totally encircled the planet. Professionals captured data with Cassini and ground based telescopes such as NASA’s IRTF and ESO’s VLT, the latter at thermal wavelengths. A dark vortex formed in the turbulence back from the head of the storm. Amateurs also tracked the evolution of the storm including the dark vortex.

By October 2011 the storm was dissipating, the vortex was shrinking and most thought that would be the end of it. Through 2012, amateurs tracked a dark spot at the latitude of the Great Storm. Following solar conjunction in Dec 2012, a dark spot was again recovered by amateurs, and followed right through 2013.

The amateur data through 2012 was analysed in amateur spreadsheets and drift charts. When Kunio Sayanagi (Cassini ISS) merged this amateur data with his Cassini ISS data and drift chart, it became apparent that this dark spot was in fact the surviving fossil of the original dark vortex, formed by the Great Storm, the longest lived continually tracked feature of its type ever at Saturn. Another outstanding example of what Pro/Am collaborations can achieve.

A quick run down of the activities of the Radio Astronomy Section of the ASV with a report on progress with the 30 foot Radio Dish project and its future.

Ken Le Marquand, ASV President and Convenor of NACAA XXVI, will officially open the event, and introduce the Keynote speaker.

Power point presentation showing the "wow" images of objects in the solar system. These amazing images are the latest available from sources such as NASA and ESA.

Power point presentation involving methods used to take narrowband images of the Sun in different wavelengths. Equipment and processing methods used by the presenter will be highlighted.

Crucial to our understanding of variable stars is the accurate measurement of their brightness variations over time. Experienced amateur astronomers equipped with CCD cameras are now contributing professional quality data, often in pro-am collaborations. However astronomical CCD cameras and associated additional hardware, such as photometric filters and automated filter wheels, are quite expensive.

In recent years standard commercial DSLR cameras have been employed as relatively low cost stellar photometers with surprisingly good results. So much so that the American Association of Variable Star Observers (AAVSO) ran a workshop in 2013 to write a DSLR Observing Manual to promote their use in variable star observing.

DSLR cameras equipped with standard telephoto lenses are well suited to monitoring stars that are too bright or with small amplitude that are difficult for CCD or visual observers, respectively. However, there are both advantages and disadvantages to DSLR cameras which will be briefly illustrated with examples from observing programs on eclipsing binary and Cepheid variables. This work has been in collaboration with Australian and New Zealand amateur and professional astronomers and has led to several publications.

After two visits to Prague in recent years I have obtained the photos and knowledge, with research, to discuss the astronomical life and times of Tycho and Kepler around 1600. I have also seen the display at Benatky Palace outside Prague and been inside the famous Prague Clock.

Team Occultation (Sydney and Canberra chapter) continues the tradition of observing lunar graze occultations. Despite the advances of technology like data from the lunar Kaguya orbiter, the lunar graze, observed by a team of determined astronomers, is still a true test of Lunar Theory and stellar catalogues.

This presentation summarises the grazes observed since NACAA XXV and suggests that a Melbourne chapter of Team Occultation would be a welcome addition and rival.

RS Gru and BS Aqr are bright, high amplitude monoperiodic delta Scuti stars with periods of 3.5 hr and 4.75 hr, and amplitudes in V of 0.6 and 0.4 magnitude respectively. Previous studies of both stars revealed changing periods, a recognized feature of some delta Scuti variables. It was previously suggested that an unseen companion of BS Aqr may account for the pattern of period change.

For BS Aqr, 5 times of maximum were determined by DSLR photometry between 7 September and 26 October 2013, and were combined with 22 other times of maximum obtained by other observers between September 1973 and August 1995. An O-C diagram of these 27 times of maximum revealed a linear ephemeris which when calculated had the following light elements (with standard errors in brackets):

Tmax = HJD 2,456,543.0250(0.0005)+0.1978227646(0.0000000096)E

For RS Gru, 16 times of maximum were determined by photoelectric and DSLR photometry between September 2007 and July 2013, and were combined with 12 times of maximum obtained by three other observers between October 2003 and October 2010. An O-C diagram of these 28 times of maximum revealed a quadratic (second order polynomial) ephemeris which when calculated had the following light elements:

Tmax = HJD 2,452,920.02019(0.00064)+0.14701118(0.00000011)E+2.513 (0.466)E2

The ephemeris indicates that the period of RS Gru is increasing at a rate of 6.244(1.157)x10-8 d/yr, or 42.477(7.870) cycles/yr. To the author's knowledge this is the highest rate of increase in the pulsational period of this type of delta Scuti star ever recorded.