In 1702, Pierre de La Hire made a curious observation about Earth's umbra. In order to accurately predict the duration of a lunar eclipse, he found it necessary to increase the radius of the shadow about 1% more than is warranted by geometric considerations. Although the effect is clearly related to Earth's atmosphere, it is not completely understood, since the shadow enlargement seems to vary from one eclipse to the next. The enlargement can be measured through careful timings of lunar craters as they enter and exit the umbra.
Such
observations are best made using a low-power telescope and a clock or watch
synchronized with radio time signals. Timings should be made to a precision of
0.1 min. Record the instant when the most abrupt gradient at the umbra's edge
crosses the apparent centre of the crater. In the case of large craters like Tycho and Copernicus, record the times when the shadow
touches the two opposite edges of the crater. The average of these times is
equal to the instant of crater bisection.
Note that all predictions presented here use Danjon's rule of shadow enlargement (see: Shadow Diameters and Lunar Eclipses). In particular, the diameter of the umbral shadow has been calculated assuming an enlargement of Earth's radius of 1/85 to account for the opacity of the terrestrial atmosphere. The effects of Earth's oblateness have also been included.
Total
Lunar Eclipse of 2007 March 03
Table 1
Crater Immersion and Emersion Times for the
Total Lunar Eclipse of 2007 March 03
UT of UT of
Immersion Crater Name Emersion Crater Name
|
Crater |
In/entrada |
Observed |
Crater |
Out/Salida |
Observed |
|
Grimaldi |
|
|
Grimaldi |
|
|
|
Billy |
|
|
Aristarchus |
|
|
|
Campanus |
|
|
Kepler |
|
|
|
Kepler |
|
|
Billy |
|
|
|
Tycho |
|
|
Plato |
|
|
|
Aristarchus |
|
|
Pytheas |
|
|
|
Copernicus |
|
|
Timocharis |
|
|
|
Pytheas |
|
|
Copernicus |
|
|
|
Timocharis |
|
|
Campanus |
|
|
|
Dionysius |
|
|
Aristoteles |
|
|
|
Manilius |
|
|
Eudoxus |
|
|
|
Menelaus |
|
|
Tycho |
|
|
|
Plinius |
22:21 |
|
Manilius |
00:37 |
|
|
Goclenius |
22:22 |
|
Menelaus |
00:41 |
|
|
Plato |
22:23 |
|
Dionysius |
00:45 |
|
|
Taruntius |
22:27 |
|
Plinius |
00:45 |
|
|
Langrenus |
22:27 |
|
Proclus |
00:56 |
|
|
Eudoxus |
22:28 |
|
Taruntius |
00:59 |
|
|
Aristoteles |
22:31 |
|
Goclenius |
01:01 |
|
|
Proclus |
|
|
Langrenus |
|
|