The Moon is a harsh mistress, 28 June 2010

2010/06/28

Yes, I know…I’m blatantly ripping off the title of one of my favorite books, but there is a reason for that, as I’ll explain momentarily. Right now, though, enjoy the photo.

D80-CHI_Luna01_2010-06_24B

Photo Information:

Camera: Nikon D80
Lens: Nikon Nikkor 300mm f/4 [1]
ISO Equivalency: 100
Color Setting: Vivid

The reason I used the title above is that photographing the Moon from the surface of the Earth is actually a bit harder than one might imagine. Often, it is not entirely apparent that the Moon is a rather fast-moving object…but it is. From a relative standpoint, it appears to be stationary, but wait around just a few minutes with a long telephoto lens pointed at it, and you will notice that the Moon has moved in even that short span of time. [2] Additionally, the Moon is obviously quite a bright object in the night sky; if you’re looking to capture some stars in the background, forget about it. [3] Even scattered clouds may not show up once you’ve properly set your exposure for the Moon itself. Even with making adjustments, it is not quite a simple matter of checking the light meter and using those settings; to capture any detail on the surface, you’ll have to underexpose the shot – by as much as two or three stops.

As for the latter part of the title, Western lore tends to depict the Moon as a feminine deity, [4] which is just fine with me; I always felt that moonlight was more attractive than sunlight, anyways.

Enjoy.

Notes:

[1]: Yes, you read that right. With the 1.5x crop factor for using full-frame lenses on a DX sensor, the effective focal length of the lens is a whopping 450mm. Now, repeat after me, “Woohoo!”

[2]: Given that the Moon’s orbital velocity is approximately 1 km/sec, this isn’t surprising – for reference, 60 mi/hr = 96.6 kph; (96.6 km/hr) / (60 min/1hr) = 1.61 km/min; (1.61 km/min) / (60 sec/min) = 0.027 km/sec. Or the other way around, the Moon is moving at an average velocity of 3,600 kph, or 2,237 mph. Pretty fast for a giant ball of iron and assorted minerals, ain’t she?

[3]: I mentioned this last year in regards to the notion that the photographs from the Apollo Lunar Missions were faked, specifically, the mention that none of the photos taken on the surface of the Moon had stars in the background. The answer, of course, is fairly straightforward: since the Moon has almost no atmosphere, [*] there is very little atmospheric gas to absorb or scatter the incident sunlight. As such, the surface of the Moon has a very high reflectance value, not so much because the material itself is highly reflective, but because there is so much more light hitting the surface. This being the case, the exposure settings need to be adjusted to account for this additional reflected light, and due to the high contrast between the very bright surface and the dark background of space, the stars are easily lost between these two.

[*]: Yes, the Moon does have an atmosphere; apparently, it only adds up to approximately 10 metric tons of gas, or approximately 100 trillionth (1/100,000,000,000,000) the density of Earth’s atmosphere at sea level. Effectively, the Moon is surrounded by hard vacuum.

[4]: Luna (Roman), Selene (Greek), Chang’E (Chinese), and Coyolxuahqui (Aztec), to name a few. And no, I have no idea how to pronounce the last one. Do you?

[5]: For those of y’all who are unfamiliar with the title, the book is The Moon Is A Harsh Mistress, by Robert A. Heinlein; it is one of my favorite books, written by one of my favorite authors. Well, it’s actually a toss-up between this one and Starship Troopers.

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