of Leitz Trinovid 10 × 40 binoculars modified for use in space to aid in Earth observations. The SX-70 was used to take pictures of the Extreme Ultraviolet monitor by Dr. Garriot, as the monitor provided a live video feed of the solar corona in ultraviolet light as observed by Skylab solar observatory instruments located in the Apollo Telescope Mount. Computers Skylab was controlled in part by a digital computer system, and one of its main jobs was to control the pointing of the station; pointing was especially important for its solar power collection and observatory functions. The computer consisted of two actual computers, a primary and a secondary. The system ran several thousand words of code, which was also backed up on the Memory Load Unit (MLU). The two computers were linked to each other and various input and output items by the workshop computer interface. Operations could be switched from the primary to the backup, which were the same design, either automatically if errors were detected, by the Skylab crew, or from the ground. The Skylab computer was a space-hardened and customized version of the TC-1 computer, a version of the IBM System/4 Pi, itself based on the System 360 computer. The TC-1 had a 16,000-word memory based on ferrite memory cores, while the MLU was a read-only tape drive that contained a backup of the main computer programs. The tape drive would take 11 seconds to upload the backup of the software program to a main computer. The TC-1 used 16-bit words and the central processor came from the 4Pi computer. There was a 16k and an 8k version of the software program. The computer had a mass of 100 pounds (45.4 kg), and consumed about ten percent of the station's electrical power. Apollo Telescope Mount Digital Computer Attitude and Pointing Control System (APCS) Memory Load Unit (MLU). After launch the computer is what the controllers on the ground communicated with to control the station's orientation. When the sun-shield was torn off the ground staff had to balance solar heating with electrical production. On March 6, 1978, the computer system was re-activated by NASA to control the re-entry. The system had a user interface that consisted of a display, ten buttons, and a three-position switch. Because the numbers were in octal (base-8), it only had numbers zero to seven (8 keys), and the other two keys were