Total Lunar Eclipse 2001 January 9

Image Analysis

Byron Soulsby, Calwell Lunar Observatory

Introduction

Several high quality images have been measured to determine the change in umbral geometry during this eclipse in accordance with the description given in the Appendix to my analysis of the total lunar eclipse of 2000 July 16.

The images eclipse2GS.gif to eclipse5GS.gif, were processed as shown below to 256 greyscale and saved as *.PICT files to allow the measurements to be made using the Image Analyst software.

Measurements

Here is one of the Image Analyst software measures captured from the Macintosh screen:

Umbral Change

The measurements were made with each image calibrated to a semi-diameter of the moon of 0.2786 degrees with the following results:

Image	Time h:m (UT)	Umbral SD degrees at Grayscale	Moon's SD degrees	Moon to Umbra degrees
eclipse2GS	19:38	0.715 at 193	0.2786	0.495
eclipse3GS	21:11	0.575 at 59	0.2786	0.432
eclipse4GS	21:35	0.642 at 60	0.2786	0.482
eclipse5GS	21:53	0.515 at 67	0.2786	0.426

To ascertain if these changes in umbral semi-diameter are related to variations in conditions of the upper atmosphere during the time of this eclipse, such as cloud cover, dust or ozone layer elevation, a QuickBasic computer program ViaX.BAS has been run to find the topocentric umbral semi-diameter for the observing site at Tom… ovsk… 63, 979 01 Rimavsk… Sobota, Slovakia, Europe at longitude 20deg 00min 24.5sec E (coordinate system: S42 - Pulkovo), latitude 48deg 22min 28.5sec N and at an elevation of 228 m.

Results

The expected umbral topocentric umbral semi-diameter is shown for the observing site where the four images were taken. The measured values of the umbra from the images are compared in the Excel graph below:

Discussion

From the graph the measured umbral semi-diameter (SD) appears to fall well below the computed topocentric semi-diameter (Fi) as the eclipse approached fourth contact. The polynomial trend lines for each component indicate a maximum change in umbral geometry of around 0.1 degrees at 21.7 hours.

The effect of cloud cover or other changes in the upper atmosphere during the eclipse could account for this reduction in measured umbral semi-diameter. Other data suggests that at a longitude of 90 degrees from the observing site where the effect on the umbra cast onto the Moon's surface would be greatest, show small upper atmospheric change during the eclipse with a decrease in cloud cover near fourth contact.

Conclusion

It is shown that from the few image measurements taken that the geometry of the umbra did change during the period of this eclipse. Such a change is supported by data reported by others.

References

The theory for topocentric computation is shown in the Appendix link given above, and evidence concerning cloud cover is reported by Toms.