TOTAL LUNAR ECLIPSE
SEEING:- ANTONIADI II-III
TRANSPARENCY:- 3; 4 later
CONDITIONS:- CIRRUS; MIST; ICE HALO; FREEZING AIR
WIND:- EASTERLY FORCE 2
Magnitude of Eclipse:- 1.195
|Partial Eclipse Begins||18:42UT|
|Total Eclipse Begins||19:50UT|
|Total Eclipse Ends||20:52UT|
|Partial Eclipse Ends||21:59UT|
The dome shutter track was frozen as was the shutter flap. The shutter drive however was able to shear the frost line along the shutter's lower edge where it butted the flap, and along the trapped track.
This was the first opportunity I had to photograph a well placed Total Lunar Eclipse, in ideal conditions, since January 9th 1982, exactly 19 years earlier. That eclipse was similar in circumstance, yet brighter despite the eruption of Mt.St.Helens in 1980. This total lunar eclipse was higher in the sky, of similar duration, [ the Moon only just fully entered the umbra] and was darker despite there being no major volcanic eruption since Mt. Pinotubo, Philippines & Chance's Peak, Montserrat in the early '90's. I estimated the brightness of the 1982 eclipse as Danjon 3, and this one as Danjon 2. The brightness factor for photography at mid totality was 2 in 1982 but only 0.05 in 2001.
Sky conditions during the partial phase were misty and hazy due to cirrus. The cirrus cleared completely during the end of the penumbral phase, remained perfectly transparent throughout totality and the waning partial phase, after which a heavy mist formed at ground level, visibility about 500 yards.
I recorded both partial and total phases using a 400mm f/4.5 Tele Ennalyt telephoto lens & Kodachrome 200, exposures 1/5s to 8s, median 4s; and the 10-inch f/10.6 Calver, & Elite 400 uprated to ASA800, exposures 1/4s to 8s, median 4s. Image size in the 400mm telephoto was 4mm and in the Calver 26mm. I took 36 exposures using the 400mm and 72 through the Calver at prime focus. The 400mm was equipped with an Exakta Varex IIa & the Calver a Pentax LX. Both were fitted with reflex finders, the VXIIa had a fine ground glass screen and the LX a magnear eyepiece & aerial screen. Both camera's shutters were operated with metal braided cable releases.
I observed & photographed the occultation of SAO79386 a mag 6.5 star and the appulse of 63GEM, which skirted the eclipsed Moon's darker limb that extended further into the umbral shadow. Other stars occulted during totality were as follows:
SAO 79418 mag 9.07 20:25:20UT
SAO 79425 mag 7.98 20:31:59UT
SAO 79421 mag 9.40 20:36:59UT
SAO 79410 mag 7.15 20:53:40
SAO 79435 mag 9.14 graze
SAO 79432 mag 8.81 21:00:40
These times were obtained from a computer simulation run on my PowerMac & SkyChart2000 using an imported HIC catalogue, corrected for parallax, refraction and nutation, and reduced to epoch of date. Of these stars I only observed the occultation of SAO79421 due a complete preoccupation with securing exposures.
The evening was bitterly cold, approximately 28¡F, but nowhere near as cold as January 9th 1982 when there was 3 inches of frozen snow & ice and an air temperature of only 12¡F. However being inside my observatory dome sheltered from the icy breeze made a big difference. Whilst during the 1982 eclipse I had to photograph it outside using my Quantum 6 Maksutov-Cassegrain, for this eclipse I could use my freshly refurbished 10-inch f/10.6 Calver which provided a much more stable platform, and enabled three rolls of 35mm slide film to be reeled off in a comparatively trouble free fashion.
The observing session lasted from 18:30UT until 22:15UT and given the inclement conditions was a real tour-de-force, putting the newly commissioned Calver through its paces. The telescope is extremely stable once the worm drives are engaged; firing off brief exposures through either SLR camera was very easy. There was no accompanying vibration or focus or image shift whatsoever. The only problem was due to moisture from my eye condensing on the Pentax LX viewfinder magnifying eyepiece. Focusing became easier later in the eclipse when the Moon passed close by 63 Geminorum. Focusing on the eclipsed Moon at prime focus was very difficult because of the dim low contrast image. Focusing on the proximate bright star was simple. I was delighted with the Calver's performance. The synchronous 1MHz crystal controlled VFO RA drive tracked the Moon at 46.465Hz very accurately. Barely any RA corrections were required. My observing companion, Anthony Marshall, assisted in adjusting the telescope in DEC.
The visual aspect to the eclipse was striking. One edge of the eclipsed disc, that furthest from the centre of the umbra, remained bright, with a peculiar lilac pearlescent chiaroscuro, redolant of the terrestrial landscape during a total solar eclipse. I observed the latter part of the partial phases using a 44mm wide angle Erfle, giving approximately x55. It was very hard to see any detail in the darkest part of the disc. The disc's hue only became discernible at the onset of totality. It was a very deep ruddy, almost blackish-red hue.
The "experts" speculated that because the previous decade had been free of major volcanic eruptions there would be little dust in the outer atmosphere and therefore less scattering of red light, and more sunlight, including red light would be refracted into the umbral shadow cone leading to possibly one of the brightest lunar eclipses for many years; at least since the mid 1980's. However last year's lunar eclipse on January 20th was a brighter one, whereas those of September & April 1996 were quite dark and those of August 1989 and January 1982 were relatively bright despite the eruptions of Mt. St. Helens in 1980 and several other eruptions in the late 80's, all of which ejected millions of tons of ash & gas above the tropopause.
There are other factors that effect the brightness of a lunar eclipse besides the amount of red scattering due to dust in the stratosphere and mesosphere. The magnitude of the total phase, i.e. how close to the umbra's centre the centre of the Moon's disc approaches at mid-totality is perhaps the most significant factor. Of secondary importance is the degree of cloudiness of the troposphere around the earth's limb as seen from the Moon, and the altitude of the Moon above the observer's horizon and the local atmospheric transparency. The last two factors are by their nature, on the time scale of total lunar eclipses, essentially random.
It would be interesting to compare the Danjon factor with eclipse magnitude and its proximity to preceding major volcanic eruptions. Perhaps someone reading this would have the time to ferret out the data and conduct a statistical analysis to determine the correlation coefficient.
mid-eclipse appulse with 63Gem
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