CALWELL LUNAR OBSERVATORY
CALWELL LUNAR OBSERVATORY
A list of computer generated crater timings for this eclipse are given * here . The times are given in UT to the nearest second for each primary contact of the umbra and for the centre of 60 lunar craters to be eclipsed by the umbra.
The craters listed are a useful selection for timing analysis and include those previously observed at earlier eclipses, they have been taken from a data base of 7,400 features. If other craters are observed, please add these additional feature contact timings to your observer's report.
Crater timings are used to determine the enlargement of the umbra due to the effects of refraction of the upper atmosphere of the Earth, to investigate the geometry of the umbra, especially its oblateness, and to determine change in the height of the atmosphere throughout each eclipse. The values of % umbral enlargement and umbral oblateness are used to form an improved lunar eclipse ephemerides (Reference 1) for application to Cannons of lunar eclipses.
It is important, except for point objects such as mountains, to time the observed contact of the umbral edge with the leading and following rim of each crater for immersion and emersion, to provide suitable input data for my Crater Timing Reduction program. However, if single or mid-crater timings only are recorded, then these should also be included in your report as these can also be analysed.
The use of a large lunar map is recommended to assist in crater recognition. The Rand McNally Official Map of the Moon Including the far Side of the Moon is most suitable for this, and Antonin Rukl's Atlas of the Moon is an excellent reference for crater recognition.
All visible features should be timed even if not shown in the list of predictions, as over 7,400 lunar feature coordinates are available for the analysis of all observations. Difficulty will probably be experienced in determining the actual umbral edge, but it is suggested that a consistent estimate of the most dense edge is used (where the rate of change in shadow density is judged to be greatest), to achieve consistent timing of features. The desired accuracy of the timings is ± 6 seconds, but should be reported to one second or better if possible.
To assist in your umbral edge estimate and recognition of features to be timed, use a low magnification so that a full image of the Moon is seen in your telescope's field of view.
The author (Reference 2) has obtained CCD video records of nine recent lunar eclipses. These have proven to be valuable for computer analysis of images captured from VHS PAL or NTSC format and Video-8 PAL records using a frame grabber and shareware software for statistical measurement of the shape of the umbral edge and its change, as shown in the last figure.
Any video records of the lunar image during this 1997 eclipse would be useful data in continuing this research.
It is important to provide timing on these records synchronised with any available short wave radio timing source such as WWV, WWVH or other signal which should also be part of the audio track on the video record.
When visually timing crater contacts, remember that an accurate timing source is also needed, and tape or video recordings made with a short wave radio timing with the observer's aural report is a good method.
As the recognition of craters and other features timed can be critical, and many appear different under eclipse conditions, it is advisable to practice recognition on several nights before the eclipse to sharpen your identification of features. The use of numbered adhesive labels placed on a lunar map as mentioned above, is a useful method, particularly for emersions where the crater is not fully visible during umbral transit.
Please remember to complete the observer's Report Form and forward this with your detailed observations as soon as possible after each eclipse.
The analyses of each eclipse will be placed on these pages, see the last eclipse of 1997 March 23-24 reported * here.