November 8, 2003 - Lunar Eclipse

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lunar eclipse september 1996

November 8th 2003
Lunar Eclipse

On November 8th, weather willing, we will be able to view a total eclipse of the Moon. The Moon rises as the Sun sets just before 5 pm PST. Already eclipsed the Moon will gradually regain its brightness over the course of 3 hours. It's a perfect opportunity to capture some snapshots of the event. Read further to find out what happens during the eclipse and how to capture it photographically.

 
David Lee - image and text
 
 
Brenda Stuart - illustration
 

 
What's Happening

A total lunar eclipse occurs when the Earth comes between the Sun and the Moon. During a lunar eclipse the Moon's position traverses the Earth's shadow. The Moon's first contact with the Earth's shadow is at the outer band of the shadow called the penumbra. The light falling on the Moon is progressively blocked until at the moment of total eclipse the Moon is completely in the darkest central area of the Earth's shadow called the umbra. At the point of total eclipse the process starts to reverse itself until the Moon is totally out of the Earth's shadow. 

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eclipse diagram showing umbra and penumbra 

Glossary

limb - the outer edge of the Moon

penumbra - the outer band of the Earth's shadow

umbra - the darker central area of the Earth's shadow

partial eclipse - the Moon is positioned within the penumbra

total eclipse - the Moon is positioned totally within the umbra 

 E C L I P S E   T I M E L I N E
First detectable change Moon's eastern limb enters the penumbra 2:15pm PST
Partial eclipse - 1st Contact Moon's eastern limb enters the umbra 3:32pm PST
Total eclipse - 2nd Contact Moon entirely in the umbra;
deep orange red

5:06pm PST

Totality 5:18pm PST
Total eclipse - 3rd Contact 5:31pm PST
Partial eclipse - 4th Contact Moon's western limb leaves the umbra 7:04pm PST
Eclipse ends Moon leaves the penumbra 8:22pm PST
 

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Observing Tips

What do you need?

Everything from your eyes, binoculars and telescope are suitable. Bear in mind this is a long process and at this time of year dress warmly if you want to be comfortable.

Find yourself a location that has a clear horizon view of the east especially if you wish to view during the early stages.

Keep a log of what you see and note the time. Pay attention to how much of the light on the moon is obscured and if there are any colouration changes. During the total eclipse the Moon will take on a deep orange-red colour. The colour of the Moon is a function of contaminants in the atmosphere and varies from year to year.
 

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Photographic Tips

Equipment
Any camera with the capability of setting shutter speeds and aperture settings manually will do fine. The ability to use interchangeable lenses will be an advantage for more detailed images of the Moon. For the darker parts of the eclipse, eg. totality you should use a tripod support for best results. If you have access to a telescope you can try capturing the event using prime focus techniques through the telescope optics.

Film
Film is very much a personal choice. Today's emulsions are very fine-grained and detailed in spite of their rated speeds. Don't be shy to use ISO 400 or even ISO 800 film. Given the speed of the optics you are using you may have to opt for a higher speed film anyway. For astronomical subjects using negative film I've always been a great fan of Fuji Super G 800, you'll need to go to a camera specialty store for this one. Another good film is the more current and easily obtained film Fuji Superia 400. For slide film I understand the Kodak Ektachrome Professional E200 is an excellent film with good pushing capabilities although at the expense of increased grain.

Technique
The simplest eclipse pictures can be taken with a manual camera and a normal lens, preferably supported by a tripod. For best results use a cable release to minimize vibration. Images taken in this fashion result in a small lunar image. This is why it is preferable to use a telephoto lens to photograph the Moon. For a 35mm camera try a 200mm lens or something close to this, even better a 500mm lens or higher. You may also use teleconvertors to increase magnification, these typically come in 1.4x and 2x strengths. Their downside is they reduce the effective aperture of your optical system. A 1.4x teleconvertor will decrease your effective exposure by 1 stop, a 2x teleconvertor will decrease your effective exposure by 2 stops. Work out your effective aperture of your optical system ahead of time so you don't have to think about it on the night of the eclipse.

Example:

 Focal Length  Aperture Effective Focal Length
with 2x teleconvertor
Effective Aperture
with 2x teleconvertor
 180mm  2.8  360mm  5.6
 480mm  6.8  960mm  13.6

To achieve any higher magnification than what is stated above you will have to use a telescope at prime focus. For this your manual camera does need to have the capability of using interchangeable lenses. For prime focus you will use the telescope optics as your interchangeable lens. To attach your camera to your telescope you will need two things a T-adapter that fits your camera and a telescope camera adapter that fits your telescope. The telescope camera adapter is designed to fit in the focusing tube of your telescope and is threaded to accept the T-adapter of your camera. With the magnification involved with telescopic optics it is likely that you will need to use a tracking mount. Preferably the mount should be able to track at lunar speed as opposed to sidereal but if the shutter speeds chosen are shorter than 1 or 2 minutes this is not critical.

Exposure times are the next consideration. The following exposure times are based on a medium speed film and an effective aperture that would be common with a long telephoto and teleconvertor combination. Exposures may vary with your equipment based on ISO speed of film used and effective aperture. The Danjon Lunar Eclipse Luminosity Scale has been included to provide better guesstimates for totality.

Exposure Times: based on ISO 400 speed film

Full Moon  1/250 second at f/16
1st Contact  1/125 second at f/16
2nd Contact  2 seconds at f/16
Totality
*see table below
L = 4 : 8 seconds at f16
L = 3: 30 seconds at f16
L = 2: 2 minutes at f16
L = 1: 8 minutes at f16
3rd Contact 2 seconds at f/16
4th Contact 1/125 second at f/16

* Danjon Lunar Eclipse Luminosity Scale

 L = 1 dark eclipse; lunar surface details distinguishable only with difficultly
 L = 2 deep red or rust coloured eclipse; central part of the umbra dark but outer rim relatively bright
 L = 3 brick-red eclipse; usually with a brighter (frequently yellow) rim to the umbra
 L = 4 very bright copper-red or orange eclipse, with a bluish, very bright umbral rim

If you are using a digital camera the same techniques apply. Use ISO settings of 400 or 800 and the longest telephoto setting you have.

The exposure times are recommendations. The tricky part of lunar eclipse photography is choosing which part of the Moon to expose for ... the light or the dark part. The difference in exposure is close to 8 stops. I usually use an exposure that works for the majority of the lunar surface. Deciding when to switch is a personal choice. Remember the cardinal rule about photography ... bracket. Always try exposures plus and minus your chosen exposure. This gives you a better chance of usable results. Let's hope for clear weather. If you have any questions please send email to David_Lee@telus.net .

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