What is the difference between a chronograph and a chronometer?

A chronograph is a watch with hands that display hours, minutes and seconds, together with a mechanism for measuring elapsed time by means of a central chronograph hand, which records seconds, and totalisers for the minutes and hours (not mandatory).
A chronometer is a watch whose movement has obtained an official rate certificate from the COSC (Official Swiss Chronometer Testing Institute) after having passed precision tests in different positions and at different temperatures. These tests are conducted over a 15-day period.

What are the functions of the pushbuttons on a chronograph?

The push buttons serve to start or stop the function, and to reset the chronograph. Generally, the push button at 2 o’clock is to start and stop the chronograph function.
There are some chronographs with mono-pusher as well in the OMEGA collection.

What is the function of the helium escape valve on the Seamaster Professional watches?

Why a helium escape valve? When carrying out work at great depths, professional divers stay in a diving bell  for  several  days,  breathing  a mixture of gases containing a high proportion of helium. The pressure is gradually increased to reach the pressure at the working depth. The divers, still inside the bell, are then lowered to the working site. They leave the bell to carry out their work.
Once  their  work  is  complete,  they  re-enter  the  bell,  which  is  then raised to the surface. Pressure is then returned to atmospheric levels and this is when the valve must be opened (only for deep-sea dives lasting several days). 
The helium molecules diffuse and penetrate the material of the gaskets. The quantity is sufficient to push out the crystal during the return to  atmospheric  pressure. To  avoid  this,  the  Seamaster  Professional Diver is equipped with a valve specially developed by OMEGA.

How do I use the tachymeter on Speedmaster watches?

The desired information is read off between the central seconds hand of the chronograph and the tachometer scale, over a maximum duration of 60 seconds.
Example of using the tachymetric scale to calculate the speed of a car:
Record the time the car takes to cover a distance of 1 kilometre. Read off the tachymetric scale the speed indicated by the central seconds hand. In the case it stops at 120, the car is travelling at 120 km/h.

What is the difference between a self-winding and a manual-winding movement?

The difference between these two movements is the way in which the watch is wound up. Manual-winding watches must be wound by hand every day, whereas self-winding watches are wound by an internal rotor which responds to wrist movements. Self-winding watches usually have a power reserve of at least 40 hours and therefore have sufficient energy reserves to maintain a stable rate when the watch is not being worn (e.g. overnight).

Where does the luminosity of my watch’s dial and hands come from?

OMEGA uses Super-LumiNova material for the dials and hands of its watches. The Super-LumiNova material takes its luminosity from daylight or any artificial source of light. The watch should therefore be exposed to bright light in order to ensure the luminosity of the dial and hands in the dark. Please note that the intensity and duration of the luminosity may vary depending on the watch model, the colour of the Super-LumiNova material and the time of exposure to the source of light.

What are the service intervals?

The service frequency depends on the use of the watch and the environment in which it is worn. The water resistance can, for example be affected by ageing of the gaskets or by an accidental shock. Therefore, we recommend that you have the water resistance checked once a year and a complete service performed every 5 to 8 years.