Observed Brightness of the Moon during the

Total Lunar Eclipse on Nov. 08-09 2003

 

By Helio C. Vital

 

 

A third-degree polynomial fit (r2= 0.937) to 27 REA`s observations made using the reversed binoculars method yielded the following equation for the Moon`s magnitude (m) around totality. Estimates from the following observers have been included: Alexandre Amorim (blue); Willian C. Souza (red); Helio C. Vital (green); Felipe E. Hodar (yellow); Jose G. Aguiar (black) and Antonio Coelho (orange).

 

m = - (2.364x10-5 Dt3 + 2.327x10-3 Dt2 - 3.317x10-2 Dt + 3.40)

 

Dt being the time interval in minutes since 01h18.5m UT.

 

The equation has been used to generate the figures listed in the following table:

 

Nov. 09 (UT)

Fitted Magnitude

Nov. 09 UT

Fitted Magnitude

00h20m

-8.5

01h19m

-3.4

00h40m

-6.7

01h20m

-3.3

00h50m

-5.6

01h21m

-3.3

01h00m

-4.6

01h22m

-3.3

01h05m

-4.2

01h23m

-3.3

01h06m

-4.1

01h24m

-3.3

01h07m

-4.0

01h25m

-3.3

01h08m

-3.9

01h26m

-3.3

01h09m

-3.9

01h27m

-3.3

01h10m

-3.8

01h28m

-3.3

01h11m

-3.7

01h29m

-3.3

01h12m

-3.7

01h30m

-3.4

01h13m

-3.6

01h31m

-3.4

01h14m

-3.6

01h32m

-3.5

01h15m

-3.5

01h33m

-3.5

01h16m

-3.5

01h38m

-3.9

01h17m

-3.4

01h48m

-5.1

01h18m

-3.4

01h58m

-7.3

 

 

Our preliminary analyses of observations made by REA/Brazil seem to indicate that:

 

1.        The eclipse was a very bright one with a minimum at magnitude 3.3 (0.2) which is consistent with L=3.6 in the Danjon Scale. That was to a certain extent expected since the Moon would be crossing the outer umbra almost grazing its edge internally and since no major volcanic eruption has occurred in the last two years.

 

2.        Our correlation between eclipse magnitude and the brightness of the Moon derived from eclipses not affected by volcanic aerosols predicted -3.0 (0.3) for the minimum magnitude of the Moon during that event. Thus based on Richard Keen`s studies we conclude that apparently no significant amount of volcanic ashes is currently present in Earth`s atmosphere.

 

3.                   The Moon`s light curve shown above exhibits a very interesting asymmetry with minimum brightness occurring 6.5 minutes after mid-eclipse (01h18.5m UT). Apparently the umbra was brighter during the first half of totality (which occurred at higher umbral angles). That could be an indication that ozone depletion over Antartica may have played a significant role in the characteristics of the umbra during the eclipse, as predicted by Erich Karkoschka in his article for the 1996 Sep. issue of Sky&Tel. According to his simulations ozone darkens and shrinks the size of the umbra. Consequently a depletion in the ozone layer would produce just the opposite effects.

 

4.                   Other observed features of the eclipse also support that suspicion: our preliminary data analysis (still under way and soon reductions of timings from several other REA`s observers will be added) is consistently yielding umbral enlargement factors that are significantly greater for immersions than for emersions. In addition, no conspicuous bluish outer umbra was noticed around the beginning of totality (U2) though telescopic observations and photos show it just before the end of totality (U3) at lower umbral angle. According to Karkoschka, the bluish coloration near the edge of the outer umbra is due to stratospheric absorption of red light by ozone molecules. In addition, during crater emersions the edge of the umbra (which monitored mid-latitude southern regions) looked more sharply defined than during immersions (which probed the south polar regions). That effect had also been predicted by Karkoschka.

 

5.                   This year the ozone hole almost was close to its record size in September exceeding the area of Antarctica as shown in the figure below.

 

 

Lunissolar: the Site of the Eclipse Section of the Brazilian Observational Astronomy Network (REA)


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