The result of ten years of research and development the IWC Portuguese Siderale Scafusia is an astronomical watch that is a technical tour de force and the most complicated watch created by IWC so far. Its a showcase watch that IWC hopes will attract new customers and also a way of displaying IWC`s technical prowess.

A reason for IWC deciding on an astronomical watch would be that astronomical watches have shown to be the most desireable watches to collectors. Astronomical complications possess a mystique and an allure due to their visually exciting displays, rather than their practical application. Given the watches special astronomical functions IWC chose the Paranal Observatory in Chile for its launch.

The new IWC Calibre 94900 movement has over 500 pieces and features a “constant-force” tourbillon, a new technological advancement .

Since the power provided by a mainspring varies dependant on its wound state, the purpose of a constant force escapement is to maintain a constant power rate. This in turn increases the watches accuracy.

The large tourbillon which displays the seconds adorns the front of the watch on the left, along with a subdial at the 12 O’clock position which displays sidereal time (true star time) , solar time and power reserve are also indicated.

The rear of the IWC Portuguese Siderale Scafusia is no less impressive (click image top for larger view) and displays various astronomical data. A section of the night sky is represented by a celestial chart , the location of which is chosen by the customer. According to IWC its capable of displaying between 500 and 1000 stars.

This celestial chart rotates depending on the position of the stars in relation to your position on earth. Surrounding the chart are small hands that indicate sunset/sunrise, day/night, sidereal and solar time. A perpetual calendar is also included at the top of the dial, it displays a count of what number day it is and the leap year.

A substantial 46mm case was needed to house the watches highly complicated movement and is 17.5mm thick. Available in in 18k white, red gold, and platinum it comes in a special box that features a crown winding mechanism so that it is always powered.

IWC have created a nicely designed mini site to go with watch that provides more detailed information here

IWC Portuguese Siderale Scafusia Specification

Portuguese Sidérale Scafusia Watch Ref. 5041

Features

Mechanical movement, new balance with two adjustment cams and two adjustment weights, Breguet spring, two barrels, constant power tourbillon

Dial side displays 24-hour display (sidereal time), sidereal time and solar time can be set separately, power reserve display

Rear side displays Customized celestial chart and horizon, sunrise and sunset display, sidereal time and solar time, day, night and dusk display under celestial chart, perpetual calendar with display showing leap years and number of day

Movement

Calibre 94900

Frequency 18,000 A/ h / 2.5 Hz

Jewels 56

Power reserve 4 days (96 h)

Winding hand-wound

Watch

Materials Case material as specified by customer (e.g. platinum or red gold)

Strap as specified by customer with IWC folding clasp

Glass Sapphire, convex, antireflective coating on both sides

Back see-through sapphire-glass back

Water-resistant 3 bar

Diameter 46 mm

Height 17.5 mm