Why Earth Photos from the Moon Have Starless Skies

Ever wondered why photos of Earth from the moon show a starless black sky? The complete absence of stars in those photos has puzzled many, fueling conspiracy theories and misconceptions. 

But the truth behind those starless skies is far less mysterious than it seems.

How Cameras Capture Light

Apollo astronauts used film cameras to capture their iconic images on the moon.^(ref) To understand why these photos lack stars, we need to dive into the basics of camera exposure. 

Film is a light-sensitive material that reacts to the amount of light passing through the camera’s lens. Two key factors control this light intake: aperture and shutter speed.

• Aperture: The aperture is like the pupil of your eye, widening or narrowing to let in more or less light. A smaller aperture restricts light, while a wider aperture allows more light to reach the film.
• Shutter Speed: This controls the duration for which the film is exposed to light. A faster shutter speed means less exposure time, while a slower shutter speed allows for longer exposure.

The Challenge of Capturing Bright & Dim Objects

Photographers must carefully balance aperture and shutter speed to achieve the desired exposure. The brightness of the subject plays a crucial role in this decision.

Brighter objects require a smaller aperture and faster shutter speed to avoid overexposure, where too much light washes out the details.

The Lunar Environment

The lunar environment presents a unique challenge. The sun’s light on the moon is harsh, with no atmosphere to diffuse it. 

This makes the lunar surface and objects like spacesuits incredibly bright. To capture these elements clearly, astronauts needed a smaller aperture and faster shutter speed.

Stars vs. Subjects

This setting, however, comes with a trade-off. The faint light from distant stars simply cannot compete with the overwhelming brightness of the lunar landscape. 

As a result, stars fail to register on the film, leaving the background a starless black.

Capturing Stars in Space

Not all space photos lack stars. Some Apollo missions included experiments where astronauts deliberately left the camera’s shutter open for longer periods. In these images, you can indeed see pinpricks of starlight, though often overshadowed by the overexposed moon or Earth.

For example, the Cassini mission to Saturn offers a counterpoint to the moon landing photos. Two stunning photos showcase the possibility of capturing stars in space:

• Tethys in Eclipse: This image reveals Saturn’s moon Tethys partially eclipsed by its shadow. While the focus is on the moon, the background reveals faint streaks of light-–stars captured during the long exposure necessary to capture Tethys in the dim light.^(ref)
• Iapetus by Saturn Shine: Here, Saturn’s moon Iapetus is illuminated by light reflected from Saturn itself. Again, the long exposure required to capture this faint illumination also allowed the camera to pick up the subtle streaks of starlight.^(ref)

Unlike the handheld cameras used on the moon, Cassini remains locked onto its target while making slight adjustments during exposure. This movement, combined with the long exposure time, causes stars to appear as streaks as they slowly move across the sky.

Indeed, the absence of stars in most moon landing photos isn’t a conspiracy or a hoax. It’s a simple consequence of the camera settings required to capture the astronauts and the brightly lit lunar surface.