Accompanied by photocopies of Longines Siderographe Ref. 6081 description and operating instructions in French and photocopies of Heinrich Pavel's article "Der Siderograph", Alte Uhren und moderne Zeitmessung 5/86 edition.
The Siderograph is named after the expression "sidereal" or star time and was originally developed for astro-navigation.
The sidereal time watch is an ordinary watch which is speeded up by adjustment of the mechanism in order that it will indicate 24 hours of sidereal time for every 23 hours 56 minutes approximately of solar time. A Siderograph is a combination of a clock and a navigation instrument and keeps a reference time equivalent to the time at 0° Greenwich longitude.