After ten years of intensive research, IWC has succeeded in uniting solar time with sidereal time, together with astronomical displays, in a single watch.

The front of the IWC Portuguese Sidérale Scafusia features the solar time, the sidereal time, power reserve and a very large tourbillon as seconds display.

The Portuguese Sidérale Scafusia is not only an impressive sight from the front, but also from the reverse side, with its imprinted night sky and perpetual calendar.

The calendar is shown in the form of a circular cut-out and counts the days of the year continuously: the 1st of January is day 1, the 31st of December day 365; or, in the case of a leap year – indicated by the letters LY, number 366.

This is joined, on the edge of the case back, by a further display that shows the current time of day, the sidereal time as well as sunrise and sunset with arrows in a 24-hour rhythm.

Finally, at the centre, is the night sky. The horizon, engraved in yellow, shows the night sky as the owner himself sees it at a location of his choice.

IWC’s engineers use the coordinates of the individual location to calculate the angle of the horizon and then machine the cams which control the sunrise and sunset display.

This means that the customer is not only the owner of an extraordinary watch but also has his own personalized constellation showing the night sky at the geographical position of his choosing.

Also linked to this is the background formed by the night sky, which has a polarization filter that makes it appear grey by day and blue by night.

The first thing that strikes the viewer is the centrally positioned celestial chart which, thanks to a polarization filter, appears grey during the day and blue at night.

Each piece is built to orde and the yellow horizon line is individually calculated for a location specified by the watch’s owner.

IWC has had this watch in development for a decade and is the most complicated timepiece they’ve ever built.

In view of the degree of customization and the complexity of the design and mechanism this involves, buyers will have to wait approximately one year for delivery.