CALWELL LUNAR OBSERVATORY
CALWELL LUNAR OBSERVATORY
This is an initial report concerning the observations of the partial lunar eclipse of 1997 March 23-24. This eclipse was visible in South America, the United States of America, the United Kingdom, Africa and Western Europe.
The interest in this eclipse was high with more than 45 e-mail queries received on the day of the eclipse and my Internet Service Provider recorded over 2,000 "hits" on my web page in the last 3 days leading up to this celestial event and a phenomenal further 38,600 for the rest of the eclipse week.
The Universidade Federal de Pernambuco, Reclife, Brasil again provided direct Netcam images of this eclipse, one example taken at local time 24d 01h 57m 14s, or 24d 04h 57m 14s (Universal Time), some 2 hours into the partial eclipse, is given in the image immediately below.
The analysis of addition images downloaded from Brazil and the first data sets from South Africa and Brazil on crater timing reductions are included in my report on this page below.
Abstract
Images of a partial lunar eclipse have been measured by image analyst techniques to determine the geometry of the umbra. A procedure has been developed to compute the topocentric umbral sizes for each observing site from geocentric data. The topocentric values are compared with the image umbral measures to determine change in the size of the umbra during the 1997 partial lunar eclipse of March 23-24 observed by a telescope/CCD camera in Brazil with images transmitted to the Internet.
Keywords: lunar eclipse, umbra, topocentric value
1. INTRODUCTION
Images of lunar eclipses have been measured by image analyst techniques for the semi-diameters of the umbra and moon to determine the geometry of the umbra. As these images are topocentric, a procedure has been developed to compute the expected topocentric umbral semi-diameter for each observing site from geocentric data. The topocentric values of umbral size have been compared with the measurement of images downloaded from the Internet to determine change in the umbra during the 1997 partial lunar eclipse of March 23-24.
2. PROCEDURE
The partial lunar eclipse of 1997 March 24 was observed at Recife, Brazil by the Universidade Federal de Pernambuco where the team lead by Jose Fernando Tepedino provided "real-time" CCD images of the eclipse via the Internet. The eclipse was also observed by one astronomer in South Africa, and he recorded a series of crater timings for analysis.
Captured frames from the real time images and Internet records have been digitised and measured using the commercial software, Image Analyst Version 8.0, running on a Macintosh IIci computer. A full description of the theory and method are described * here.
3. MEASUREMENT COMPARISON
A typical measurement frame or image is shown in figures 1 and 3 below and the analysis of the measurements of captured frames, from the one hour period of clear weather from the Internet images provided by the Universidade Federal de Pernambuco, in Brazil are given in the chart of figure 2 supported by Dale Ireland's data in figure 4.
In these figures the measured umbral radii (Ru) and the topocentric values are compared with each measurement of the apparent umbral semi-diameter taken from the captured images. The computed slant angle ([Delta]') of the umbral edge to the lunar plane, also defined in Soulsby, 1995, 1996, is included for each image. The departure of each measured diameter from the computed topocentric value shows the change throughout the eclipse. This is also shown as a smoothed (dashed) line in figures 2 and 4, trend lines in the change in umbral size.
4. CHANGE IN UMBRAL SIZE
By comparing the measured semi-diameters of umbral images with the computed topocentric values, dynamic change in umbral geometry is detected. The 1997 March 23-24 data suggests that a large change in umbral geometry occurred during the lunar eclipse, probably due to variation in transparency and/or cloud cover in the Earth's atmosphere.
5. INTERNET RESPONSE
The author has an World Wide Web home page on the Internet which provides full details concerning each lunar eclipse. It includes links to many aspects of lunar eclipse observing for the casual observer and the serious astronomer with tips on telescopic observing and CCD imaging.
The responses before and after this eclipse were PHENOMENAL and included many requests for specific information on how and when to observer the eclipse from many countries, particularly from the United States. Two moving responses received by e-mail after the eclipse were:
"Thank you for the information. The moon "came up" a bit later here due to our elevation and the elevation of the surrounding mountains but it was BEAUTIFUL. We walked up our hill to 3000 ft in order to see it earlier and there was not a cloud in the sky! So Hale-Bopp with its long tail was the companion to the moon's eclipse - two amazing wonders in the sky as well as millions of stars. When the moon was just a sliver silver crescent with a red belly we started back towards our house for warmth and watched the rest with the spotting scope. It got down to -4 C this night. And this morning it went to bed under the mountains in the pink glow of sunrise - full and beautiful."
Another very unique response was as follows:
"Here in Puerto Vallarta the eclipse was partial, began to 9h 10m PM of the Sunday 23 of March of 1997 and ended to 0h 27m PM of the Monday 24 of March of 1997. For the afternoon was overcast, to the dusk began to be cleared and when beginning the eclipse was cleared (there were not clouds).I could observe all the eclipse to simple sight from the balcony of my house, seemed me a wonderful phenomenon, the sky is opaque a little, the fowl began to sing in the finishes phase of the eclipse. We had a very quiet and transparent night. I wait that this information serves you, because I not have more equipment than my sight, I am solely an admirer of the natural phenomena. I don't speak English, I use a translator program for power to understand."
There many other equally touching messages which has made this a very enjoyable eclipse for me even though I could not see it, except through the power of the Internet.
Figure 5 summarises the overall Internet response with over 40,600 "readers" logging in and browsing the Lunar Eclipse Observer - Home Page. during the eclipse week.
6. CRATER TIMING REDUCTIONS
To date ten groups of observers have reported contact of the umbra with surface features of the moon, known as crater timings. It is expected that further data will be received for analysis in the coming weeks. Those received and analysed are given in the two summary tables below, the first concerning the percent enlargement (%E) of the umbra and the second concerning the observed oblateness of the umbra.
Details of individual crater timing observations and reductions can be found * here.
|
OBSERVER |
NUMBER |
MEAN %E |
MEAN ERROR |
NUMBER |
MEAN %E |
MEAN ERROR |
|
|
|
|
|
|
|
|
|
ZYL KOOS VAN |
5 |
2.4068 |
0.3076 |
|
|
|
|
VITAL HELIO C. |
28 |
2.2867 |
0.0773 |
28 |
2.1059 |
0.0747 |
|
FERNANDES PAULO & COELHO ANTONIO C. A. |
13 |
2.4444 |
0.1482 |
8 |
1.8413 |
0.2433 |
|
GARCIA J. ANTÔNIO C. & AGUIAR MARIA Y. F. |
27 |
2.2662 |
0.0756 |
29 |
2.0987 |
0.0879 |
|
PADILLA F. ANTONIO |
14 |
2.3064 |
0.0933 |
12 |
1.7461 |
0.1454 |
|
RIBEIRO ANGELO. C. & GODINHO MARCO J. F. |
24 |
2.2089 |
0.1327 |
21 |
1.8904 |
0.1183 |
|
VARGAS LUCIMARY |
18 |
2.4828 |
0.1146 |
|
|
|
|
PUJOL FRANCISCO |
5 |
2.5374 |
0.6629 |
|
|
|
|
TREVISAN EDVALDO J. |
14 |
1.9780 |
0.1174 |
12 |
2.0544 |
0.0955 |
|
FREDERICO FUNARI |
17 |
2.5511 |
0.1268 |
1 |
1.4419 |
0.0000 |
|
OBSERVER |
TYPE |
No |
Ecc |
Re |
Rp |
Fo |
SD |
SK' |
|
|
|
|
|
|
|
|
|
|
|
VITAL HELIO C. |
|
|
|
|
|
|
|
|
|
IM |
O |
29.00 |
0.0660 |
0.7237 |
0.7222 |
- |
0.0448 |
0.4599 |
|
IM |
T |
29.00 |
0.0997 |
0.7111 |
0.7076 |
200.5774 |
0.0649 |
1.0506 |
|
EM |
O |
27.00 |
0.0584 |
0.7234 |
0.7221 |
- |
0.0236 |
0.3592 |
|
EM |
T |
27.00 |
0.1052 |
0.7120 |
0.7080 |
180.1495 |
0.0413 |
1.1698 |
|
FERNANDES PAULO & COELHO ANTONIO C. A. |
|
|
|
|
|
|
|
|
|
IM |
O |
13.00 |
0.2204 |
0.7239 |
0.7061 |
40.6706 |
0.0051 |
5.1815 |
|
IM |
T |
13.00 |
0.0908 |
0.7099 |
0.7070 |
241.9781 |
0.0649 |
0.8709 |
|
EM |
O |
8.00 |
0.1576 |
0.7260 |
0.7169 |
80.0513 |
0.0068 |
2.6325 |
|
EM |
T |
8.00 |
0.1015 |
0.7115 |
0.7079 |
193.6544 |
0.0461 |
1.0882 |
|
GARCIA J. ANTÔNIO C. & AGUIAR MARIA Y.
F. |
|
|
|
|
|
|
|
|
|
IM |
O |
30.00 |
0.0696 |
0.7209 |
0.7192 |
- |
0.0041 |
0.5115 |
|
IM |
T |
30.00 |
0.1024 |
0.7115 |
0.7077 |
190.3678 |
0.0666 |
1.1070 |
|
EM |
O |
26.00 |
0.0839 |
0.7251 |
0.7225 |
283.3099 |
0.0342 |
0.7438 |
|
EM |
T |
26.00 |
0.1059 |
0.7120 |
0.7080 |
177.9298 |
0.0417 |
1.1844 |
|
PADILLA F. ANTONIO |
|
|
|
|
|
|
|
|
|
IM |
O |
15.00 |
0.1547 |
0.7366 |
0.7277 |
83.0203 |
0.1104 |
2.5383 |
|
IM |
T |
15.00 |
0.1078 |
0.7122 |
0.7081 |
171.5049 |
0.0736 |
1.2287 |
|
EM |
O |
11.00 |
0.1908 |
0.7362 |
0.7227 |
54.4561 |
0.0800 |
3.8698 |
|
EM |
T |
11.00 |
0.1045 |
0.7118 |
0.7079 |
182.7774 |
0.0425 |
1.1529 |
|
RIBEIRO ANGELO. C. & GODINHO MARCO J. F. |
|
|
|
|
|
|
|
|
|
IM |
O |
26.00 |
0.1474 |
0.7219 |
0.7140 |
91.5215 |
0.0059 |
2.3026 |
|
IM |
T |
26.00 |
0.1012 |
0.7113 |
0.7077 |
194.9653 |
0.0661 |
1.0809 |
|
EM |
O |
19.00 |
0.0768 |
0.7229 |
0.7207 |
338.4104 |
0.0313 |
0.6227 |
|
EM |
T |
19.00 |
0.1044 |
0.7119 |
0.7080 |
183.1519 |
0.0417 |
1.1506 |
|
VARGAS LUCIMARY |
|
|
|
|
|
|
|
|
|
IM |
O |
18.00 |
0.0995 |
0.7287 |
0.7251 |
201.5073 |
0.0731 |
1.0458 |
|
IM |
T |
18.00 |
0.1124 |
0.7129 |
0.7084 |
157.7200 |
0.0788 |
1.3361 |
|
TREVISAN EDVALDO J. |
|
|
|
|
|
|
|
|
|
IM |
O |
15.00 |
0.1195 |
0.7202 |
0.7151 |
139.5325 |
0.0040 |
1.5103 |
|
IM |
T |
15.00 |
0.1068 |
0.7120 |
0.7079 |
174.7179 |
0.0709 |
1.2061 |
|
EM |
O |
11.00 |
0.1038 |
0.7261 |
0.7222 |
184.9440 |
0.0368 |
1.1394 |
|
EM |
T |
11.00 |
0.1185 |
0.7132 |
0.7082 |
141.8860 |
0.0405 |
1.4852 |
|
FREDERICO FUNARI |
|
|
|
|
|
|
|
|
|
IM |
O |
17.00 |
0.1434 |
0.7240 |
0.7165 |
96.7390 |
0.0046 |
2.1784 |
|
IM |
T |
17.00 |
0.1020 |
0.7114 |
0.7077 |
191.6797 |
0.0693 |
1.0994 |
The interesting results are those considerably less than the expected geometric oblateness FM and these are shown as BOLD. The average of these is around 1/80 which indicates a larger umbral oblateness during this eclipse than the previously observed mean of 1/102. There is a high scatter in this data, but it is typical for a partial eclipse.
7. CONCLUSIONS
The measured umbral semi-diameters taken from the Internet images have been compared with computed topocentric values of umbral semi-diameter at the time of each image frame. Most umbral measurements are close to the computed topocentric semi-diameters.
There appears to be a measurable, but slow dynamic change in umbral semi-diameter during this partial lunar eclipse, with little scatter due to the improved image quality of the images captured by the Recife team lead by Jose Fernando Tepedino at the Universidade Federal de Pernambuco , in Brasil.
They are to be congratulated in obtaining such excellent images under extremely difficult conditions and provided me not only with useful images but with my "second" day time lunar eclipse.
These results are supported by the data obtained from the excellent photographs provided by Dale Ireland, observing in the USA. His sequence of photos were sent to me by e-mail, converted and measured. The change in umbral size had exactly the same hourly rate of change as that observed in Brazil.
8. ACKNOWLEDGMENTS AND THANKS
The author would like to express his thanks to the astronomers whom have contributed to this research by providing images and telescopic observations. In particularly to those overseas observers who provided real-time Internet images and photographs of the moon in eclipse when a lunar eclipse is not visible in Australia.
I would also like to thank and acknowledge the 40,600 Internet readers. I am now quite sure that this is the way to fully inform interested people about astronomy and in particular the wonder of lunar eclipses.
The next lunar eclipse will be visible in Australasia, Asia and Africa on 1997 September 16-17 - I hope you keep browsing the web for relevant information.
9. REFERENCES
Soulsby, B.W., 1996. Analysis of the topocentric umbra from 3 lunar eclipsesAust. J. Astr., (in print).
Soulsby, B.W., 1995, Analysis of the 1995 April 15 partial lunar eclipse, Aust. J. Astr., (6)2: 33-52.
Soulsby, B.W., 1994, Change during lunar eclipses, Proc. 16th Natn. Aust. Conv. amat. Astrer., Canberra, pp 101-114.
Meeus, J., 1991. Astronomical Algorithms, pp 263-4. Willmann-Bell Inc. 429 pp.
10. WORLD WIDE WEB AND E-MAIL LINKS
I would be happy to analyse your 1997 LUNAR ECLIPSE crater timing observations and/or video recordings, please send your results to my observatory address above, or:
To ensure that I can quickly collate and analyse your observations, please send all reports by AIRMAIL or e-mail and video tapes of the observation of the eclipse by AIRMAIL as soon as possible to:
You can also use the e-mail *input form to provide me with the details of your observing site.
Lists of computer generated crater timings for this lunar eclipse
were provided with all times given in UT to the nearest second for
each primary contact of the umbra and for each centre of 60 lunar
craters eclipsed by the umbra. The craters include those previously
observed at earlier eclipses, and 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 observers' 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.
CCD Video Records
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 below.
Any video records of the lunar image during the 1997 March eclipse would be useful data in continuing this research.
Early analysis of the Brazilian images are under way, but due to very heavy cloud it was not possible to transmit clear images at a regular time interval.
Please remember to provide the information listed in the observer's Report Form and forward this with your observations as soon as possible after this eclipse.
Name, Site location, Longitude, Latitude, Altitude (m), Postal Address or e-mail address, Instrumentation, telescope your timing source and weather conditions.
If you are able to produce video records of either 1997 eclipse, the author would be pleased to analyse these on receipt of the original video tapes if sent to his observatory address.
Please forward your site details and occultation observation details to me by: