Location
The observing location was 0.25 km south of the Mount Horner West Road at the entrance to the Mount Horner Property mid-way between Table Top Road and Piggery Lane. The map location was at Longitude 115 degrees 04 minutes 13.2 seconds East, -29 degrees 07 minutes 15.3 seconds South, at an elevation of 152 m. We were positioned just outside the true inner southern limit to observe the maximum number of Baily beads as the sun is either obscured by the mountains or revealed by the valleys of the shadow of the northern limb of the moon.
Cathie successfully recorded 28 Baily beads from the projection telescope screen and a complete video coverage was recorded from first contact to just after the last bead was made. Thirty one colour photographs of annularity were also obtained.
Instrumentation
The instrumentation consisted of three units all mounted on a single tripod. These were a Sony TR511E Handycam video recorder with X 36 optical magnification and 2 layers of aluminised mylar as a solar filter, a 40mm Unitron projection telescope with shaded screen, and a 400 X 2 mm telephoto lens with a UV filter and one layer of aluminised mylar solar filter with a Canon command back photographic camera. The slide film used for 31exposures was Fuji Velvia 50 ASA at f/6.3 and 1/1000 s.
Weather conditions
The site was dust free even though a very strong wind blew from the south-west throughout the eclipse. The sky was very clear without clouds for the complete eclipse. The temperature was around 30 C. To offset the effects of the strong wind the instrumentation was set up adjacent to the car (see my slide 32).
Results
A video recording was made throughout the eclipse starting at first contact, included parts of the eclipse to annularity and a complete coverage of annularity in an attemp to capture Baily beads. Cathie observed the projection telescope screen and made an audio recording during the eclipse of the Baily beads seen. The Canon camera was used to capture coloured slides from after first contact to just after the last bead seen. The tables list these observations. In Table 1 as recorded by video and in Table 2 as recorded on the audio tape. All times are given in UT taken from the pre-set Sony cam-recorder timing signal which was found to be 33 seconds fast when compared with a short wave timing signal after the event.
Video record
The abbreviations used before annularity are: BFL = bead forming left cusp (South), BFT = bead forming top (centre of arc) and BFR = bead forming right cusp (North), after annularity they are BFB = bead forming bottom cusp (North), BF Middle = bead forming at centre of arc and BFT = bead forming top cusp (South). The first estimates from the video record of the timing of Baily beads and photographic exposures from the Sony video timing are given here.
Audio record
The audio tape was recorded by Cathie Soulsby observing the 40 mm Unitron projection screen. The times of the 28 Baily beads observed were found using a programmable HP41CV calculator STOP WATCH function and then corrected for any tape recorder drift and the 33 seconds fast Sony timing.
The observations near annularity have been carefully analysed to provide the lunar limb profile Watt's position angle for most bead timings using a specialist program developed by David Herald. With this additional data from our Baily beads, it is hoped that any change in the diameter of the sun can be accurately computed by Dr Alan Fiala of the US Naval Observatory.
Here is a typical Baily bead shown by the program, the first image is the computer screen and the second the observing site co-ordinates and elevation with the third image the actual bead (Cathies number 5) enlarged near the cursor arrow:
Baily Bead Prediction
The time of appearance of Baily Beads can be predicted using the computer program outlined above. Most of the beads can be observed, but we managed to record many but not all, due to the difficulties associated with the instrumentation. Here are four graphs which show the beads identified by observation related to the predicted Watts angle of the lunar profile. Graph a from 7h 23m to 7h 27m with 2 beads, Graph 1 from 7h 27m - 4 beads, Graph 2 from 7h 28m - 10 beads and Graph 3 from 7h 29m - 5 beads. The identified beads will help in refining the Watts limb charts and hopefully provide data for the USNO to determine the true size of the sun at during this eclipse.
Conditions
Wind effected the instrumentation and hand guiding of the tripod was not ideal as adjustment in altitude was not smooth enough. The video image was kept toward the top-right to ensure that the sun's image was seen fully on the projection screen for the audio record. Collimation of all three instruments was carried out before the car trip of about 400 km to the site, some slight movement must have occurred during the travel.
Dust was not a problem as we were in a quiet traffic area up-wind of the entrance road to the Mount Horner property with the added benefit of shade of many tall trees while not actually observing.
Acknowledgements
Special thanks are due to William Lees, the Mount Horner Property Manager for his kind permission for us to set up in an ideal location. The assistance of Jim Blanksby and David Herald in the provision of survey maps of the area, and the advice from Ken Jordan concerning photographic film and exposure is also acknowledged.
Special thanks is extended to David Herald for his specialist computer program which allowed the determination of the Watts angles for each Baily bead timed near annularity.
