Partial Lunar Eclipse 2006 September 7/8
Measurements of umbra with Digimizer and true time of first primary contact
Theodore Lunar Observatory
for crater timing reductions click here
for a collection of emails with images click here
for the measurement of the penumbra click here
for a paper on the Analysis of 54 Lunar Eclipses click here
for a hand guided Movie for 2m 31s click here
Size of the UmbraSeveral still images were taken with my Panasonic NV GS-15 movie camera and these have been measured for the semi-diameter of the umbra using my new measuring engine Digimizer.
The first image taken at 04:10:06 AEST (or 18h10m06s UT) gave a best fit circle for the umbra of 0.775° with the Moon calibrated at 0.2787°.
The time shown is 10 seconds slow, it should be 4:10:06 AEST, and the date should be 8.9.2006.
Other images have been measured in a similar manner all giving a semi-diameter of the umbra near to that shown above. The expected size of the umbra from Fred Espenak's data is 0.7742°. There is an Excel Chart here showing the computed Umbral Oblateness for this eclipse produced using my latest program ViaX7.exe.
Time of First Contact
I also took images with a Sony TR 511E video camera which had imperfections in exposure and focus, but good enough to estimate time of first primary contact. Here is an image taken just 7 seconds after the expected time of first contact at 18h05m18s (UT), where the umbra cannot be seen:
Here is another image taken at 18h06m48s (UT), where the umbra can be seen at the south east corner indicating first contact:
The first image was taken near the time of first contact found by adopting an umbral oblateness value of 1/298.26 (the Earth's geoid value), the second image was taken at the time of first contact using my new value of umbral oblateness of 1/102. This new value was found from data arising from the reduction of 12,000 crater timings made by many observers for 50 lunar eclipses analysed by this observatory.
Here are some processed images from the Panasonic camera:
From video by Dave Herald
These images show first primary contact occurs at my predicted time using an umbral oblateness of 1/102 also supporting the findings above. The following four sets of images clearly show the normal and "find edges" appearance before, during and after first contact.
At 18:03:20 the edge is continuous and the Moon is not in contact with the umbra.
This image was taken at the predicted time given by Fred Espenak, but the edge in the image on the right is still continuous, indicating that first contact has NOT yet occurred.
At 18:06:48 the Moon has just contacted the umbra.
At 18:16:15 the Moon has clearly penetrated the umbra.
Produced by the Theodore Lunar Observatory Australia, 2007 June 20/updated 2008 January 25.