A Half-Gigabyte View of the Moon

Ever since NASA's Lunar Reconnaissance Orbiter began circling the Moon at low altitude in mid-2009, planetary scientists and the public have marveled at the incredible trove of observations it's been beaming back to Earth. Most often in the spotlight are the jaw-dropping closeups of Apollo landing sites by the Lunar Reconnaissance Orbiter Camera (LROC). It can resolve the surface at 2 feet (0.5 m) per pixel — good enough to reveal even the paths worn in the lunar soil by the astronauts' boots.

The Moon up close &mdash; <i>very</i> close
A new 24,000-pixel-square mosaic from NASA's Lunar Reconnaissance Orbiter shows the Moon's nearside as never before. Click here for a larger (but not full-size!) version; a labeled version is here.
NASA / GSFC / Arizona State Univ.
The work of LROC's wide-angle camera, which provides surface context for those incredible narrow-angle shots, has largely gone unheralded … until now. This past week the team released a new mosaic of the Moon's near side taken entirely with wide-angle frames. Acquired during a two-week period in December, the 1,300 black-and-white frames create a full-disk mosaic measuring 24,000 pixels across. Gulp!

"As the Moon rotated under LRO's orbit," explains LROC team leader Mark Robinson (Arizona State University), "the ground track progressed from east to west (right to left in this mosaic)." The image run was timed to keep the Sun high up in the lunar sky but not straight overhead (its altitude varied from 69° to 82°). This created enough shadowing to define crater rims and other topography crisply, unlike the shadow-free view that we see during a full Moon. The combined image shows slight banding where the 1,024-pixel-wide swaths were stitched together.

Rupes Recta on the Moon
A close-up of Rupes Recta (usually called the Straight Wall) from the new LROC mosaic of the lunar nearside. Located near the eastern edge of Mare Nubium, this steep-faced scarp is about 70 miles (114 km) long.
NASA / GSFC / Arizona State Univ.
Weighing in at just 2 pounds (0.9 kg), LROC's wide-angle camera is small enough to fit in your hand. It features an aperture only 1.2 mm across and a focal length of just 6 mm (for visible-light work). Yet from LRO's very low orbit, currently only 20 miles (30 km) up, this mighty mite can pick out surface details as small as 250 feet (75 m). Click here to view the specifications for LROC's wide- and narrow-angle cameras.

The image looks dark because Robinson and his team have kept the Moon as it really is: dark. On average, the lunar surface reflects only about 12% of the sunlight that strikes it. So a full Moon really isn't dazzlingly bright — it only looks that way to our eyes because of the contrast with the black sky around it.

If your computer's up to it, you can download the full half-gigabyte mosaic here.

17 thoughts on “A Half-Gigabyte View of the Moon

  1. Anthony BarreiroAnthony Barreiro

    This is a beautiful portrait of the moon. The consistent angle of illumination gives it a very natural, even though physically impossible, appearance. I would love to have a more thoroughly labeled copy of this picture to use as a map.

  2. Ken Musgrave

    Thank you for a great article, Kelly, but I feel obliged to correct this statement:

    “So a full Moon really isn’t dazzlingly bright — it only looks that way to our eyes because of the contrast with the black sky around it.”

    This is not true. The moon is a dusty surface, and as such has a very strange BRDF (bidirectional reflection distribution function; this four-dimensional function relates altitude and azimuth of incident light to altitude and azimuth of reflected light) The moon, as a dusty surface, is a strong retroreflector–that is, it reflects light preferentially at 180 degrees to the angle of incidence (backscatter), like a car or bicycle reflector–hence the full moon is significantly brighter per unit area than at other phases.

    Sorry to be such a geek, but the knowledge of this factoid got me and my grad student Larry Gritz a moonlighting job modeling the moon for the film Apollo 13 when we were at George Washington University researching computer graphics.

    Perhaps more strangely still, dusty surfaces tend to reflect light preferentially *tangent* to the surface, regardless of the angle of incidence of the illuminant. Look at near-moon Apollo photos and you can readily see that this is the case. Surfaces seen tangentially appear unnaturally bright. This explains much about the appearance of the moon at all phases.

    Try it in a computer simulation, if you have the fortitude. It works. Got me a job doing special effects at Digital Domain on films like Titanic and Dante’s Peak.

    -Prof. F. Kenton “Mo” Musgrave

    PS: I’m delighted to, after some 30 years as a huge4 fan of S&T, be able to make a contribution!

  3. Al Wilson

    Uh oh, think I need to upgrade! 🙁 After 30 minutes of spinning beachball activity, my 2-year-old iMac became unresponsive and I had to pull the plug out of the wall to reset it…

  4. Emily Windsor-Cragg

    Re-rendering your LRO image, further development shows more details and a deeper perspective.


    As you can see the Moon is not a surface: it is a double-hulled container with transparent “curtains” forming vertical slits (as refrigeration panels in a warehouse).

    I have used colors to bring out depth; but of course, these are false hues. And I will not comment on details which have become visible now.

    🙂 EEWC

  5. Emily Windsor-Cragg

    The silly part of this photo is that it is STILL 72 PIXELS PER INCH, and all they did was BLOW IT UP, ENLARGE IT to the size of a family-room-size RUG, 28FT BY 28FT.

    But the pixel-by-pixel RESOLUTION is still lousy; there is no greater DETAIL in the larger version; and it pixellates almost immediately if you try to enlarge it.


  6. Jon Hayden

    Great Image! I have not found a way to open it other than in Windows 7 using Preview from explorer. No other programs will open it. Also it would be greatly appreciated if you could supply a mirror (left to right) of this image that could be used when at the scope. I cannot open in any program that i have that can accomplish this.


  7. Richard Carroll

    After a 10 minute download, my WinXP machine rendered the image well using the free program IrfanView. The Alpine Valley stretched across the screen before pixels began to be visible.

  8. Chris

    I absolutely love the full resolution image. I was able to open this in Adobe Photoshop CS5 with no issue; in fact it opened pretty quickly.

    @Emily Windsor-Cragg
    Yes, the full resolution, 500GB+ image is only 72 pixels per inch, but it is still 24,000 x 24,000 pixels. This means you could print the image at approximately 28 feet x 28 feet at 300dpi (I’d love a printer that size!). Pixels per inch should only come into play if you are printing a hard copy. For viewing on a screen, a pixel is a pixel is a pixel. If it were a higher resolution (say 300 pixels per inch), it would still be 24,000 x 24,000 pixels, but you would only be able to print the hard copy at just under 7 feet x 7 feet at 300dpi.

    I’m pretty sure I have this right, but if not, someone please chime in!

  9. rodrigo

    Actually, the 72 pixels per inch are only used by programs to calculate the default size of the image in inches, should it be printed. It is useful, for example if the image was scanned, as then it has an original real size. But if the image is computer generated, as this is the case, the default resolution hardly matters, and most programs use a default of 75 dpi.

    The image measures 24000 pixels, that is the only real data.
    Then the image suggests that it is to be printed at 72 ppi, that would be 24000 p / 72 ppi = 333 inches. 27.75 feet wide, or 8.45 meters!
    Any printing software allows you to change the resolution, so if you print it at a reasonable 300 dpi you will get 24000 / 300 = 80 inches (6.66 feet, over 2 meters).
    If you have a good laser printer you may print it at 600 dpi and still get a nice 40 inches picture (about 1 meter), and then look at it using a magnifying glass. Just like the old days!

  10. John

    Ah a TIF file and an iPad. I’ve an app for that.

    As the author of a number of iPad TIF readers this 549 megapixel image was yet another challenge. Fortunately we spent a few weeks in February dealing with Petroleum well logs which can be 2530×186,000 pixels, largest we worked with was about 425 megapixels, so what’s another 100 megapixels?

    In our stable of products “Well Logs” for the iPad/iPhone is the only app that will let you open the file.


    (a) the thumbnail is wrong, oh well, math for long skinny truncate is wrong for a rectangle.

    (b) It takes about 3 hours to pre-render the TIFF into a meta-file. We’ll have desktop support for that step in April sometime.

    Still once it’s done, then re-opening is lightning fast and zoom zoom zoom…

  11. marie

    I have been in southern california deserts and colorado snow on full moon nights in isolated areas and the moon is indeed very bright you can walk run even ride quads by the moonlight alone.

  12. Randolf Richardson

    This 24,000 x 24,000 pixel image of the moon is amazing (I’m using Adobe Photoshop CS4 Extended to view it). Looking at the moon at such detail gives a much better impression of how large it is.

    Does anyone know anything about what appears to be some sort of a snow-capped mountain at pixel offset x=19250 y=12570?

    Thanks in advance.

All comments must follow the Sky & Telescope Terms of Use and will be moderated prior to posting. Please be civil in your comments. Sky & Telescope reserves the right to use the comments we receive, in whole or in part, and to use the commenter’s username, in any medium. See also the Terms of Use and Privacy Policy.


This site uses Akismet to reduce spam. Learn how your comment data is processed.