Calibre 1045 is an Omega version of the Lemania 5100 automatic chronograph movement.

Most models of the Omega Speedmaster have been hand-winding. However, Omega has created a few automatic Speedmaster watches over the years. Many of the most sought-after models use Omega's Cal. 1045, a version of the famous Lemania 5100 automatic chronograph movement.

The following Omega Speedmaster watches used Cal. 1045

• Omega Speedmaster Mark IV ST 176.0012 (1974-1977)
• Omega Speedmaster "TV Dial" ST 176.0014 (1974-1977)
• Omega Speedmaster "Tonneau" ST 176.0015/176.0016 (1974-1977)
• Omega Speedmaster Mark V (1984)
• Omega Speedmaster Automatic "Holy Grail" ST 376.0822 (1987)

One additional prototype, case number 176.0017, was created but not produced.

Cal. 1045 generally replaced Cal. 1040 (Omega's version of the Lemania 1341) in 1974. It remained in production through about 1988, when the modular Cal. 1140 was introduced.

• Speedmaster Automatic c. 1045 in Detail