Introduction
This was one of the clearest lunar eclipses ever observed, the imaged moon and umbra were distinct and with very good definition in the three video cameras used, although Peter Anderson reported with his crater timings and images that the sky transparency above Brisbane was not good. Robert & Elizabeth Price near Bethanga Victoria reported crater timings and images, and Maurice Clark near Perth WA provided many crater timings as did Stephen and Kathy Kerr with Bill Oliver of the AAQ, and Tony Dutton from Wynnum, Brisbane, QLD.
Imaging
My web page at http://www.netspeed.com.au/minnah/2000/Eclipse2000.html provided the "live" images from one CCD colour camera during the 4 hours of this eclipse. Later this page included five GIF animations from each of my three video cameras, two of which are shown here with the Canon command-backed photographic camera with a 800 mm telephoto lens
Other images were provided on floppy disk by Robert and Elizabeth Price, and scanned images from Peter Anderson. Peter Caldwell, of the ASV at www.gsat.edu.au/astrovic/eclipse also sent images such as that below;
Recent Images
More recently, several Japanese images have been received and analysed for umbral geometry with one interesing result from a composite image for 2000 July 16 where the the distance between the two focii of the ellipse for the umbra was found to average 0.0635 degrees and the mean umbral semi-diameter 0.6275 degrees, giving an effective major axis of 2a = 0.691 and an eccentricity, or oblateness of 0.0635 / 0.691 * 2, or near 1 / 22 for the assumed elliptical umbra.
Crater Timings Analysis
The crater timings received from all observers have been reduced for umbral enlargement and umbral oblateness. The results are shown in the Reductions page.:
Discussion
From the analysis of the many crater timings received the enlargement of the umbra was from 1.95 to 2.09 % very near the value expected. The more sensitive analysis of umbral oblateness from most of these crater timings showed a very wide scatter from 14 to 0.8 times the expected value.
The captured images from all three CCD video cameras used at the Calwell Lunar Observatory have been measured for the diameter of the umbra using commercial software ImageAnalyst by Automatix Inc, Bellerica MA, which allows adjustment of the histogram of umbral edge brightness and calibration of scale, using known values of the semi-diameter of the imaged moon with time. The expected umbral size has been found from a routine described in the Appendix and the measured values compared to examine change in umbral size during this eclipse. Any change relates directly to variation in the Earth's atmosphere which directly dictates the geometry of the umbra.
Discussion
From the graphs of umbral semi-diameter change shown above, it can be seen that from first to second contact there is a general increase in umbral semi-diameter of around 0.1 of a degree from 11.9 to 12.4 hours for two image sets, then the umbra size falls near to that expected.
From the graphs of umbral semi-diameter change shown above, it can be seen that from third to fourth contact the umbra size is generally near to that expected from third contact to 15.2 hours followed by a slow increase in umbral semi-diameter of around 0.1 degree from 15.2 to 15.8 hours for the image sets.
This change of 0.1 of a degree represents a possible decrease in the transparency, due to clouds, dust etc, of the upper atmosphere which casts the umbral shadow cone from the Earth to the Moon of 0.1/0.652 * 100 % = 15 %, a very large change if we assume the general height of the atmosphere is 50 km, this would be a change in height of 7.6 km.
Conclusions
Although the image measures from all three CCD video cameras show a fair amount of scatter, all values approach those of the estimated umbral size throughout this eclipse. It can be concluded that the umbra is seen as a foreshortened semi-diameter as described and that some change in the umbral geometry due to atmospheric variations throughout this eclipse can be measured, albiet with some difficulty.
Acknowledgements
I must thank those observers for their very useful contribution to this total lunar eclipse analysis, for without their data the eclipse would have been limited to a web-cast only from this Observatory on the night of this eclipse.
The above data has been re-examined using the values of expected umbral semi-diameter computed with a recently developed QuickBasic Program (ViaX.BAS). Although the change in the umbra during this lunar eclipse is very similar to that found above, the values presented here are considered to be of improved accuracy.
Results
The graph above shows the results for the change in umbral semi-diameter using computed Fi values from my QuickBasic Program ViaX.BAS.
Discussion
The sixth order polylines show similar trends for all three CCD cameras, with the first to second contact differences between the measured and expected umbral size ranging from a minimum of -0.1 degree (Mintron) to a maximum of +0.1 (450E) with a peak value of +0.3 (E511E). The trend lines for the third to fourth contact umbral differences range from +0.05 to a peak of +0.25.
Conclusion
Even though there is considerable scatter in the image measures made from all three CCD cameras, it is concluded that the size of the umbra exceeded that expected by around 0.1 degree using the result from the high resolution Mintron camera. This represents about 0.1/0.652 * 50 = 8 kilometers change in the height of the upper atmosphere during this eclipse, or a 15 % variation in the semi-diameter of the umbra.
Chart
All three observers and their CCD camera images have been re-analysed using a batch computer program ViaX.BAS with location files (*.FRA) and Besselian coordinate files (*.XYS) prepared for each of the three frame sets. The data for Soulsby came from the Sony E551E camera, that for Lindsay from the Sony 450E camera with data also shown for the Mintron monochrome camera.
The above shows 6 order polynomial trend-lines for each data set of the differences between the computed topocentric umbral semi-diameter (Fi) and the image measurements from the Image Analyst software running on the Mac IIci.
Conclusions
The overall trend in the change of umbral semi-diameter for the total lunar eclipse of 2000 July 16, from my measures is &endash;0.1 degree during first to second contact with a slightly larger value of +0.15 degree during third to fourth contact. The Japanese imaging suggested an umbral oblateness of around 1 / 20, which is within the range computed from the crater timings analysed for this.