Saturday August 27, 2011 – IWC introduced their most complicated timepiece ever, the Portuguese Sidérale Scafusia.

According to IWC, it took ten years of intensive research to achieve the horological feat of “uniting solar time with sidereal time, together with astronomical displays, in a single watch.”

“With a history already stretching back over 140 years, IWC sets a new benchmark with this watch,” says Georges Kern, CEO of IWC Schaffhausen.

The Portuguese Sidérale Scafusia has displays on both the dial side and caseback. On the dial side, at 12 o’clock, is a true 24-hour sidereal time display – accurate to +/- 11.5 seconds per year. One the back, solar time is displayed by traditional central hours and minutes hands; with the seconds being displayed by a 60-second constant force tourbillon at 9 o’clock. In the lower right quadrant of the dial is a 96-hour power reserve indicator.

What is the difference between sidereal and solar time?
On earth, time is based on the average length of a solar day; but for observation of the stars, sidereal time is used. The two types of measurement are different. Solar time is based on the average time between the sun’s passage over a given meridian, whereas sidereal time measures the time taken for the earth to complete a rotation around its own axis. The solar day is 24-hours, whereas the sidereal is about four minutes shorter than an average solar day.

On the back side, a number of astronomical functions are displayed. A customized celestial chart and horizon, a sunrise and sunset display, sidereal time and solar time, day, night and dusk display under the celestial chart, as well as a perpetual calendar with a display showing leap years and a number of days.

This mechanical masterpiece is powered by in-house made caliber 94900, a manually wound 56-jewel movement that runs at 18,000 vph (2.5Hz). The movement has a new balance with two adjustment cams and two adjustment weights, a Breguet hairspring, double power barrels (which allow for a 4-day power reserve), and a constant power tourbillon.

The case is available in either platinum or red gold, and the strap can be individually selected by the customer, a feature IWC has been offering since the introduction of Santoni straps during SIHH 2011 and includes an IWC signed folding clasp. The case measures 46 mm x 17.5 mm in height. Water-resistance is 30 meters.

Even though this highly complicated piece of horology will most likely end up in collectors’ winder equipped safes, IWC has ensured that each piece is able to withstand the rigors of daily use. Quite a feat, especially considering the delicate mechanics required to achieve this level of chronometry. (Ref. 5041)

Posted by:Jason Pitsch

Jason is the founder of Professional Watches and specializes in writing, product photography, and digital marketing.