The dark side of the moon

August 6, 2015 • 6:45 am

Have you ever seen the other side of the Moon? This is usually impossible, as the moon rotates at exactly the speed it orbits the earth, so we see only one side.

However, a GIF tweet from NASA shows it wonderfully (click on the arrow to begin):

h/t: Grania

41 thoughts on “The dark side of the moon”

    1. The best time to photograph it is when it is a crescent or a bit more. That way you can really see the details along the borders between light & dark.

  2. Someone’s gotta say it:

    ‘I’ve never seen the dark side of the moon, but heard it lots’ (PBUPF! – Praise be upon pink floyd)

    4. Breathe…I haven’t got the Time or Money to listen to such Brain Damaged stuff.

  3. I didn’t believe this image was real when I saw it this morning on Facebook, when I saw the NASA link I still thought it was handmade and not photographic. I apologise for doubting NASA.
    It’s a photo taken from a million miles away floating (is that an accurate word in a space context?) between Earth and Sun. I didn’t know anyone had a satellite out that far. The gif on the link is very special.

    2. You mention the distance…the relative size of the moon must appear a bit larger here than the true size since the shot is from a million miles away. The moon is 238,000 miles from earth so it is about 25% closer to the camera than the Earth.

    3. I didn’t know anyone had a satellite out that far.

      The DSCOVR probe that took the photo is not a satellite in the colloquial sense. It is is a satellite but it is a satellite of the sun. The probe is not orbiting the earth. It is orbiting the sun but it sits at a very special point: the L1 Lagrange point.

      This allows the probe’s orbit to be closer to the sun than the earth’s orbit yet it can still remain stationary relative to the earth.

      2. Well since it’s at L1 it’s a satellite of both the earth and sun. Everything in the solar system aside from the sun itself is a satellite of the sun.

        1. Except for those objects at escape velocity, such as New Horizon. But, I’m just being persnickety.

  4. This image nicely illustrates how dark and unreflective the Moon is compared to Earth’s more reflective clouds and oceans (Moon albedo only 0.12; Earth albedo 0.30).

    Usually photos of the Moon are exposed to make it look relatively bright.

    1. When you expose for the moon, you use exactly the same exposure you use for any fully sunlit thing on earth. (For instance, f/11 and 1/125s for Kodachrome 64 (or any equivalent paring of aperture and shutter speed). It’s sunlit, same as anything else.

      http://www.berettaconsulting.com/barbarossa/PtarmiganTrav/Ptarmigan%20Trav%20029%20Aug-1986%20Old%20Guard%20Mtn.jpg

      That shot is not photo-shopped (beyond global minor adjustments). That was back in film days and Kodachrome is not very forgiving of missing your exposure. If I had to guess, I’d say it was taken at between 150mm and 200mm at f/4 at 1/1000s or 1/500s.

      What often happens is that people photograph things on earth, close to the horizon, and those things are getting less light because the sun is very low (pretty light; but much less of it.)

      An example:
      http://www.berettaconsulting.com/barbarossa/Landscape/C%20Rockies%20052%20Sep-1981%20Jacques%20Lake%20Sunset%202.jpg

      Here’s a another shot of the moon on a particularly hazy day. 400mm lens, KR64.

      http://www.berettaconsulting.com/barbarossa/Landscape/Moonrise%20from%20Mt%20Constitution%20Summer%201990.jpg

      This shot is slightly over exposed (showing in both the moon and the white peaks):

      http://www.berettaconsulting.com/barbarossa/Landscape/Garibaldi%20026.jpg

      Here’s a handheld shot of the moon alone:
      http://www.berettaconsulting.com/barbarossa/PandJ-Family/White%20Salmon/2012/IMGP3392_rsz90.jpg

      That may be slightly over-exposed; but not very much.

        1. In-lens image stabilization. It’s pretty amazing what very fast, very tiny computers, sensors, and motors can do these days!

        2. 500mm lens (750mm equiv. to 35mm format), f/6.3, probably about 1/500.

          Cropped a lot.

          But I can shoot down to 1/60s at 500mm and still get crisp images because of the internal IS. Wonderful system. It also helps with framing the photo: The lens first auto-focuses, then switches to IS mode and you get a steady-cam effect through the viewfinder. Otherwise, the image is shaking all over the place (handheld).

          (Doesn’t work for Stephen and the other BIF photographers though — or for any other subject that is in motion.)

      3. It occurs to me that, with the recent work I’ve been doing on building ICC color profiles with a spectral model of camera sensor’s (etc.) response, I should now know how to make a photograph of the moon with exposure and color accurately rendered, no guessing or other subjective interpretation required. The main challenge will be finding a measurement of the Sun’s spectrum before it gets filtered by the atmosphere and a similar absorptive spectrum of the atmosphere itself. Be a good exercise for me to attempt….

        b&

        1. There are actual measurements of top-of-atmosphere irradiance (extraterrestrial solar irradiance) and models which deal with it. The Kurucz Solar Model is one of the older and more famous models. Kurucz naturally is with Harvard; those Hahvud folk have dominated solar research and many fields of astronomy for over 90 years.

          If you really want to see the Kurucz model you can find one incarnation here:

          http://rtweb.aer.com/

          How the solar spectrum relates to human perception of color is a whole different kettle of fish.

          1. Thanks for that! That page didn’t have what I need…but the mention of Kurucz led me on a roundabout search that included this page:

            http://rredc.nrel.gov/solar/spectra/am0/

            which includes a link to a spreadsheet with exactly what I was looking for. (Overkill, actually — but in a good way that I can easily downsample to fit my needs.)

            I’ve been thinking more about the atmospheric component…I’ve found some models and references and what-not that I could adapt…but there’s a lot of variability that depends on local conditions. And a very easy solution. Now that I’ve got the spectrum of the Sun before it hits the atmosphere, I can measure the spectrum of the Sun locally and trivially calculate what the atmosphere takes out — which is exactly the information I need. That’ll be perfect for photographing the Sun itself. For nighttime objects I’d want to make a spectral measurement of the Sun at roughly the same altitude above the horizon as the object when there’s not going to be meaningful weather variations between day and night…and, for best results, do it all north of Flagstaff where there’s less atmosphere to begin with and negligible light pollution.

            Be a little while before I can work through a couple other more immediate priorities, but should be a fun project nonetheless.

            Thanks!

            b&

        1. It was brutal to focus that thing. An SCT is so dark and the image so small and the focused has nasty backlash. I’ve since upgraded my focuser but that moon was a lot of work.

  5. We get to see the dark side every 29 days or so, at New Moon. Far or back side is more accurate (though the latter term makes us Brits snigger adolescently).

    1. Unfortunately my self-mocking xml tags <pedantry and </pedantry were invisibled by WordPress thinking they were real tagging (closing angle brackets removed here so it doesn't happen again)!

        1. No, no…don’t go. We don’t have anyone else with your exact knowledge and personality.

      2. “Unfortunately my self-mocking xml tags <pedantry and </pedantry were invisible…"

        And because we couldn't see them, we were in the dark as to whether you were serious.

    3. Not only that, but we can actually see a bit of the far side from earth – it’s a simple matter of geometry. The first full glimpse of the far side came courtesy of the Russians; radio scientists all over the world were listening to the transmissions of the Russian satellite and someone said “hey, this sounds like a facsimile transmission” and brought a recording to play back on a fax machine (the original one which used film and a beam of light). The Russians were miffed that US newspapers had photos before they even had a chance to receive a transmission.

  6. You can see a distinct dark spot on the Moon’s far side, which I believe is the Tsiolkovskiy Crater. I wonder what superstitions and religious beliefs might have arisen if the Moon had settled into an orbit with that side visible, perhaps looking to some like an eye staring down at us.

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