Longines DolceVita - Manual (Page 27)

67 Automatic watches The Lindbergh Hour Angle Watch
How to use your Lindbergh Hour Angle Watch
Having synchronised your watch with a time signal.
As an example when you check it your watch shows
4 hours, 37 minutes and 12 seconds. The equation
of time for the day in question is minus 4 minutes and
50 seconds.
Therefore move the marker situated at “15” on the bezel
4 graduations to the left. These graduations represent
the minutes engraved around the case.
Your data are as follows:
Seconds hand (centre dial) 3’
Minute hand (bezel) 10° 15’
Hour hand (main dial) 60°
As you have only turned the bezel by 4
minutes, you still have to take into ac-
count the 50 seconds (the equation of
time being 4 minutes and 50 seconds
for the day in question).
On the central dial, the 50 is opposite 12½ . /. 12½’
Greenwich hour angle of the sun
(your longitude)
70° 5½’
The space/time dial and how it works
The design of the whole of The Lindbergh Hour Angle
Watch takes into account the fact that the Earth revolves
through 360° in 24 hours, through 180° in 12 hours,
through 15° in 1 hour and through 15’ of arc in 1 minute.
Consequently:
The hour hand indicates 15° per hour. One complete
circle of the dial (12 hours) is equivalent to 180°.
The minute hand indicates 1° per 4’, in other words
15° per hour. Each of the 15° is subdivided into four
sectors of 15’ of arc. All these indications are engraved
on the rotating bezel.
One complete circle of the centre seconds is equivalent
to 15’ of arc. The rotating central dial is divided into
60’’ and 15’ of arc.