The Penumbral Lunar Eclipse of 2001 December 30

This is another Lunar Eclipse Observer SPECIAL Page

Introduction

Most lunar eclipses observed and studied by the Calwell Lunar Observatory have been either total or partial, that is where the moon passes through the most dense central part of the shadow cast by the earth, known as the umbra. In 1998 it was shown that it is possible to observe and capture images of the less dense outer penumbral shadow during a lunar eclipse where the moon enters only the feint penumbra.

As there is one penumbral lunar eclipses in 2001, my experiment to explore images of the low density penumbra is continued, where I hope to analyse the density and geometry of the elusive penumbral shadow. The eclipse is illustrated below by the diagram produced by Fred Espanak .

The latest trial images are here and an animation from the eclipse (Note: please correct times by -4 minutes 21 seconds).

One digital image of poor fucus has been analysed to show the penumbra under threshold conditions here.

The circumstances and visibility maps for the penumbral eclipse is shown below.

I hope you will try to observe this eclipse if VISIBLE from your location, browse the location map below:

Figure 1: The penumbral lunar eclipse

The beginning of this eclipse will be visible in North America, Central America, South America except the eastern coast, Greenland, extreme northwestern Europe, northeast Asia, Arctic, most of New Zealand, North Atlantic Ocean, Pacific Ocean, eastern Phillippine Sea, and Coral Sea; the end visible in North America except the eastern coast, Greenland, Arctic, northern part of Central America, Asia, Indonesia, Australia, New Zealand, the North Pacific Ocean except southeastern part, and eastern portion of the Indian Ocean. The world map above, produced by Fred Espenak, shows the area where this eclipse will be visible (in the unshaded parts).

Eclipse contact times

Exact times have been computed for the expected moon contacts or departure from the penumbra with an estimate of the variation in each of these timings using an oblateness for the penumbral equal to that observed for the umbra. This oblateness was derived from the analysis of over 30 recent lunar eclipses where a value of 1/102 has been found for the out-of-roundness of the umbra due to the oblateness of earth's upper atmosphere. These timing variations are shown in Table 1, compared with the standard contact times where the only allowance made is for the oblateness of the earth's geoid (using the classical value of 1/298.257). This classical value ignores the effects of the flattening of the atmosphere.

Table 1 : Penumbra Contact Times

Item/Date

2001 December 30

First contact (PC1)

8h 25m 42s

variation

+0h 0m 04 s

corrected contact (PC1)

8h 25m 46s

Second contact (PC2)

12h 32m 57s

variation

-0h 0m 0.3 s

corrected contact (PC2)

12h 32m 56.7s

Using the contact times of the penumbra with the moon, and by analysing images taken at these times for each eclipse, it is hoped to estimate the flattening of the penumbra and compare this value with that found for the observed umbra.

This page prepared by the Calwell Lunar Observatory, Australia 2002 January 4.

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