Lunar Eclipse Page

A lunar eclipse takes place when the Earth passes directly in front of a full Moon, thus casting its shadow on the Moon's surface. There are two parts to the Earth's shadow, the penumbra, and the umbra. The penumbra is the sunlight that passes through Earth's atmosphere. This is not enough to produce a distinct shadow, but will diminish the light reaching the Moon. The penumbra is hard to detect with the unaided eye, so it is recommended to observe the moon as a reflection off of a piece of window pane, or through a pair of sunglasses.

The umbra is the Earth's shadow proper, and makes a distinct shadow on the lunar surface. The eclipse will end when the Moon exits the other side of the penumbra. Many observers are puzzled, why the lunar surface becomes red during a total eclipse instead of black? Consider the fact that some of the Sun's light passes through Earth's atmosphere and is bent around and behind the Earth. Much of this light is scattered as blue light, and never reaches the lunar surface. Only the longer wave-lengths of light(mostly red or orange) will reach the Moon, tinting its surface in a coppery glow.

Astrophotography:

Forget about capturing lunar eclipses on your handy point and shoot, in order to produce a large enough image on a 35mm frame you will need at least 100-500mm of focal length. The following table is a rough guide of the exposures I have used for my 10" SCT and 3.1" short tube refractor. Please remember to bracket your exposures generously. Each minute of the eclipse will present changing levels of light, and different exposures will render unique results on the film plane.

	100ASA	400ASA	1000ASA
*Umbra and Penumbra Together*
f/6.3	2 sec.	1/2 sec.	1/4 sec.
f/10	6 sec.	1 sec.	1/2 sec.
Bright Total Eclipse (copper red-orange)
f/6.3	14 sec.	3 sec.	1 sec.
f/10	40 sec.	8 sec.	3 sec.
Dark Total Eclipse (brown or grey)
f/6.3	4 min.	45 sec.	15 sec.
f/10	13 min.	2 min.	45 sec.

January 20-21, 2000:

Clear skies prevailed in Southern Ontario on this date, and most of North America enjoyed a total eclipse of the Moon. All week we had experienced overcast conditions and flurries, but a cold front moved in at the last moment to clear our skies. The down side to this was the temperatures dropped to -25º C over night.

I assembled my gear into the foyer of my home early enough that I would be able to set up quickly thus decrease the cold air's effect on my batteries and lessen the chance that equipment would freeze up. Unfortunately I was unprepared for just how fast the umbra crosses the moon and spent most of the first part of the eclipse rushing to get set up. Each optical surface had a dew heater gently warming it, as I meticulously balanced a piggy-backed 3.1" short tube refractor, and Nikon camera body with 70mm lens on the top of my 10" SCT. I was unable to detect the penumbra, but the umbra was crisp and black as it raced across the face of the lunar surface. By totality I had finally polar aligned the scope and achieved a reasonable lunar tracking accuracy.

Totality began as the last tiny crescent of reflected sun light disappeared. Simultaneously the face of the Moon dimmed to a subtle red glow while the skies over head suddenly blazed with millions of stars which seemed to magically appear out of the former haze of the moon light. Just to the left of the Moon was the constellation Cancer and at its centre, M44 the 'beehive cluster'. The beehive cluster is but a diffuse glow to the naked eye, but to small telescopes or binoculars, it is a swarm of B to K spectra stars resembling its name.

Luckily I had gotten all my equipment set up before totality as it would have been impossible to focus any of the cameras on the Moon's ruddy glow. After a few shots I removed the piggy-backed 3.1" refractor as it was having an effect on the 10" SCT's tracking. I began to take a few exposures through the 10" scope varying the length of the exposures from 8 seconds to 30 seconds. I decided to check on the front corrector plate to confirm the correct setting of the dew heaters when I noticed a large ring of frost had set in around the corrector's inside diameter. I cranked the dew heaters to full power and ran to the house to retrieve a hair dryer. After gently blowing warm air over the corrector plate for 5 minutes, the offending ring of frost had been banished. This would be the first of two times this night I would under estimate the effects of the cold Canadian climate.

It was fortunate that totality lasted an hour and 20 minutes as I had plenty of time to shoot my two rolls of film. Between shots I would dash back into the garage to warm my hands under my red incandescent light bulb and sip hot coffee. It was during one of these breaks I sat and gazed up into the heavens marveling at the sheer beauty of it all. The stars in their glittering multitudes hung against a velvet curtain of black framing a ghostly, blood red moon.

It was near the end of totality that I began to prepare for the retreating umbra that I had missed during my whirlwind set up. Just as the first crescent of sunlight returned to the lunar surface my OM-1's shutter uttered a strange sound that suggested the shutter had opened, but refused to close. The camera was covered in frost. Fortunately I was able to rewind the film in the dark and save my nights work. Unfortunately I had already used up the film in the Nikon and could only watch as once again the umbra raced across the face of the Moon.

After tearing everything down again, I found myself surrounded by frost covered equipment that sat quietly thawing in the foyer. Within a half hour everything was defrosted and I herd the reassuring "click-pop" of my OM-1's shutter relaxing from its tense cryogenic state. As I have 3-years to prepare for the next total lunar eclipse over North America, I have made a small mental list of things to do differently:

All in all this total eclipse was most enjoyable and has reaffirmed my love for all things celestial. I just can't help but envy those solar eclipse chasers who always seem to be observing all things celestial from warmer climes. Below you will find the fruits of my frozen endeavors, just click on the image to see the larger version.

Astrophotography:

January 20-21, 2000:

Lunar Eclipse Links: