The Moon was brightened for the family portrait

On September 18, 1977, Voyager 1 photographed the Earth and Moon together from 11.66 million kilometres away. NASA calls it the first spacecraft image to include both bodies in a single frame.

The familiar picture is not quite a single exposure.

Voyager’s camera recorded three images through different colour filters. At the Jet Propulsion Laboratory, those records were combined into a colour picture. This was ordinary colour imaging for the spacecraft: the camera measured separate bands of light, and processing assembled them into something resembling human vision.

One further adjustment was less evenly applied. Earth was many times brighter than the Moon. If both were printed according to the same scale, the lunar crescent would be difficult to see. The Image Processing Lab therefore brightened the Moon by a factor of three relative to Earth.

That does not make the picture false. The Moon really was in the camera’s field above and beyond Earth, and each source image could record both. “Single frame” describes the spatial achievement: no diagram, montage or change of viewpoint was needed to place the two worlds together.

But the finished picture preserves one relationship while modifying another. It shows where Earth and Moon appeared relative to each other, not how bright they appeared relative to each other. The first joint portrait required local editing because the smaller subject could attend the sitting without being especially cooperative about the lighting.

Space photographs often arrive with an implied promise of directness. The spacecraft was there; therefore this is what it saw. Voyager’s portrait is more specific. A machine measured filtered light, an image lab chose how to translate it, and the word together survived both operations. Earth and Moon shared the view. To share the print, the Moon needed help.