The three Penumbral Lunar Eclipses of 2002

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 are three penumbral lunar eclipses in 2002, my experiment to explore images of the low density penumbra is continued, where I hope to analysing the density and geometry of the elusive penumbral shadow. The three eclipses are illustrated below by the diagrams produced by Fred Espanak .

 

The circumstances and visibility maps for the three penumbral eclipses are shown below.

I hope you will try to observe those VISIBLE from your location, browse the location maps below:

For my preliminary digital images of 2002 May 26 click here.

Figure 1: The first of the penumbral lunar eclipses

This eclipse will be visible in North America except in the east, Central America, South America except the extreme east, India, Australia, New Zealand, most of Antarctica, eastern Asia and the Pacific Ocean. The world map produced by Fred Espenak, shows the area where this eclipse will be visible (in the unshaded parts).

 

Figure 2: The second penumbral lunar eclipses for 2002.

Figure 3: The third penumbral lunar eclipses for 2002.

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

2002 May 26

2002 June 24

2002 November 20

First contact (PC1)

10h 12m 46s

20h 18m 40s

23h 31m 57s

variation

+0h 0m 21s

+0h 0m 22s

+ 0h 0m 40s

corrected contact (PC1)

10h 13m 05s

20h 19m 02s

23h 32m 37s

Second contact (PC2)

13h 53m 59s

22h 35m 35s

04h 01m 04s

variation

-0h 0m 08s

-0h 0m 31s

-0h 0m 20s

corrected contact (PC2)

13h 53m 51s

22h 35m 04s

04h 01m 24s

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 June 6.

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