Digital Lunar Eclipse Photography

By Chris Lane

During the early morning hours of August 28th, we will be treated to the second lunar eclipse of the year.  The first eclipse occurred on the evening of March 3rd.  If you want to document this celestial event it’s not hard to do, but patience is required.  The Web is littered with how-to articles, but here’s a summary of the techniques that I used in March.

The August Eclipse
The August 28th event will be visible across the entire United States, but viewers in the West will have the best show.  In the Midwest the eclipse will begin at 3:20 a.m. CDT and will end at 6:23 a.m. CDT.  Simply add or subtract an hour or two on either end to get the schedule for other time zones. The Moon will appear in the WSW part of the sky and will be setting in the West as dawn begins to light the sky. In the Midwest totality will still be in progress as the Moon sets.  This should present some very interesting photographic opportunities.  Expectations are that this event will be a bit duller and darker than the March eclipse.  According to Sky & Telescope, you may see a bright yellow or even blue arc just inside the umbra’s edge.  The Moon should appear very three dimensional due to this effect.

Equipment
Make sure your camera has a fully charged battery. Use a tripod and a cable or remote release. Although your exposures will not be that long, since both the Moon and Earth are moving you’ll want to minimize any additional motion. Noise should not be a big issue. Be sure to turn off IS or VR as that technology can create problems when used on a tripod. Choose your focal length depending upon the type of image you want to make. If the Moon is merely a part of a larger landscape you can go wide. If you want the Moon to be the dominant feature, go as long as you can. I prefer 300mm and up. Use your lens unfiltered and with it’s lens hood. The hood will minimize dew formation and stray light.

March 3rd Lunar Eclipse, 2007

Technique
In March I used a Canon 30D set up as follows:
•Parameters 2
•Auto-rotate:  Off
•Image Quality:  RAW
•ISO:  400
•Mode:  Manual
•Aperture:  f/8
•Drive Mode:  Single
•Review Time: 8 sec.
•Auto Power Off:  Off
•Image Stabilization:  Off
Don't rely on auto-focus or auto-exposure and shoot a series of bracketed test exposures using the Fred Espenak Exposure Guide.

Fred Espenak Exposure Guide
Fred Espenak, a.k.a. MrEclipse, is an astrophysicist at the Goddard Space Flight Center and is best known for his work on eclipse predictions. He has his own NASA website and in 1996 he developed a Lunar Eclipse Exposure Guide, an updated version of which is reproduced below.

How to Use the Exposure Guide
The luminosity of an eclipse is determined by using the following guidelines:
L = 0     Very dark eclipse. Moon almost invisible, especially at mid-totality.
L = 1     Dark Eclipse, gray or brownish in coloration. Details distinguishable only with difficulty.
L = 2     Deep red or rust-colored eclipse. Very dark central shadow, while outer edge of umbra is relatively bright.
L = 3     Brick-red eclipse. Umbral shadow usually has a bright or yellow rim.
L = 4     Very bright copper-red or orange eclipse. Umbral shadow has a bluish, very bright rim.

Choose a ISO and aperture, then go straight down into the second table to the subject you want to photograph. Except for Earthshine, exposure times longer than about four minutes are really not practical, since you don't have unlimited amounts of time before the event ends.

A final word
Don’t rush. The night will likely be warm and the event will  be a long one. Take your time and plan on chimping and making lots of exposures.

_________________

Chris

Ctein Comments: Nice article! I'd like to add a warning about long exposures. The moon is a moving target—it moves its own diameter every two minutes. Long blur-free exposures are not possible except with a tracking mount. How long an exposure can you get away with? It depends upon how sharp you want the results to be and what focal length lens you're using. For instance, with a 300mm lens, the moon's image will span a few hundred pixels in the camera. If you want the photo to be pixel-sharp, your exposure times can't be longer than about half a second. You'll probably be quite happy with something less than that critical level of sharpness. But there are limits. Even with a "mere" 10 second exposure, the moon will move 1/12th its diameter during the exposure. Outside of extreme wide angle photos, that's not likely to be acceptable. So 1/2 second is safe (except for extreme telephoto images) while 10 seconds is not (except for extreme wide angle images). Where should you be in between? It's a matter of taste. Fortunately, you'll want to bracket heavily during totality anyway. Just know your limits and don't try more than several seconds unless you're tracking on the moon with a guide scope.

Comments

[Thomas]

On a side note, I just noticed the data in the 'full moon' row is equivalent to the old 'sunny 16' rule. Many years ago an old photog told me the same sunlight that strikes the earth also strikes the moon. Interesting.

[Ctein]

Dear Thomas,

Yup, that's about the size of it.

The moon's actually about half a stop darker than a typical earthly landscape. That's a whole stop darker than middle grey-- it's not a very light object! But under the full moon, you're seeing the surface by directly incident light that backscatters strongly towards us. Brightens things up considerably. Also, no shadows!

You'll also note that the exposure increases rapidly away from full. That's due to a combination of no backscatter, shadows, and the sunlight hitting the moon at a shallower angle.

pax / Ctein

[Chris Lane]

Thomas,

You have broken the code. It is always "sunny" on the Moon (except when it's not).

Chris

[KeithB]

I have heard that you do not want to use the sunny 16 directly since you don't want the moon middle grey, you want it brighter, so you should overexpose by a stop or stop and 1/2.

(I wonder - since my kids will only see shutter and aperture values in 1/3 - 1/2 stop intervals whether they will ever get the intuitive concepts of a "stop" at all...)

[Ctein]

Dear Keith,

The "f/16" rule is an amusing coincidence, but don't get fixated on it. Remember that it is nothing more than a rule for rendering earthly scenes (an overall 13% reflectance) with "normal" tonality; it's not an absolute of photography. Definitely not of astrophotography. (Most embarrassing blunder I ever read was a supposed expert on metering and exposure recommending that people photograph Comet Hale Bopp using the f/16 rule, because it was a sunlit object about as far from the sun as the earth was. A mere three or four orders of magnitude error. I'm sure film latitude would cover it.)

How bright you want the moon in your photo is an aesthetic choice. If you're trying to make a nice telephotograph of the moon that clearly shows lunar detail, rendering it as a "middle grey" (which is a full stop lighter than the moon actually is) might be just the way to go. Maybe even half a stop darker, if you want accurate tones.

If you're looking to render it as a luminous object in the sky, you want to go to longer exposures. But remember that if you're using slide film or digital capture, blowing out your highlights is a bigger risk than losing the shadows. And camera shake and subject movement kill more lunar photos than misexposure.

In any case, you're only going to care about making ONE good photograph of the moon at any given point in the eclipse, so bracket, bracket, bracket!

pax / Ctein

[Thomas]

The old photog I mentioned in the earlier post was a real codger, and not above pulling the occasional leg. He once covered LBJ's arrival at the Nashville airport with his trusty Crown Graphic. Standing shoulder to shoulder with the traveling press corp (F's and M3's), he licked his index finger, held it up in the air, turned it about, then reached down and adjusted the camera's aperture. Oddly enough, he had plenty of elbow room after that. He called it "Tennessee windage" and, of course, his photos were excellent.
Priceless.

Thomas

[scott]

Liberty Science Center in New Jersey is sponsoring a photography contest for the Aug. 28 lunar eclipse. We welcome all entries. Details can be found here: http://www.lsc.org/getinvolved/eclipse

[Tom Eloph]

I live in San Jose, CA and while the lunar eclipse was intercepted by clouds and rain, luckily I'd shot my first lunar eclipse previously in August. The images were shot with my Canon 10D at 300mm, various exposure times... i was up all night! 6 hours and about 1000 photos. I've posted some of the best via the link.

http://www.eloph.com/dev/events.asp

Canon 10D, 300mm, f/5.6, ISO 1600, ~2 sec

Love your blog!
Tom