The Apollo Telescope Mount, or ATM, was a crewed solar observatory that was a part of Skylab, the first American space station.

The ATM was manually operated by the astronauts aboard Skylab from 1973–74, yielding data principally as exposed photographic film that was returned to Earth with the crew.

The film magazines had to be changed out by the crew during spacewalks, although some instruments had a live video feed that could be observed from inside the space station.

Some of the first Polaroid photos (an instant film-to-hard copy camera) in space were taken of a Skylab CRT video screen displaying the Sun as recorded by an ATM instrument.

In the case of the ATM, the initial idea was to mount the instrumentation in a deployable unit attached to the Service Module,[4] this was then changed to use a modified Apollo Lunar Module[5] to house controls, observation instruments and recording systems, while the lunar descent stage was replaced with a large solar telescope and solar panels to power it all.

This change saved the Skylab program when a problem during launch destroyed one of the workshop solar panels and prevented the other from automatically deploying.

This is a chart describing an example of this: A backup ATM spare (instruments were mounted to this) was restored and put on display in 2015 at the Steven F. Udvar-Hazy Center in Chantilly, Virginia, US.