Portugieser Sidérale Scafusia


Taken together, the choice of materials for the case, the five different colours for the dial, the various colours for the appliqués and straps and the material used for the straps, result in over 200 different design options.

  • Price
  • Reference 5041
Watch Front
  • Case in platinum, 18-carat red gold or 18-carat white gold
  • Mechanical movement
  • Hand-wound
  • 2 barrels
  • Breguet spring
  • 96-hour power reserve when fully wound
  • Power reserve display at 4.30
  • Constant-force tourbillon and small seconds at 9 o’clock
  • Sidereal time at 12 o’clock
  • Sapphire glass, convex, antireflective on both sides
Watch Back
  • Perpetual calendar with leap year display and absolute day of the year
  • Celestial chart showing horizon, ecliptic and celestial equator
  • Indication for day, night and twilight
  • Display for sunrise and sunset
  • Coordinates of chosen location
  • Sapphire glass
  • Case height 17.5 mm
  • Diameter 46 mm

— The 94900

Learn More

  • Setting

    The beauty of a classic dial with two brand new features

  • Power Reserve

    Winding the watch twice a week is enough

  • ESO Paranal

    European Southern Observatory (ESO), Paranal, Chile. The world's most advanced visible-light astronomical observatory

  • Calibre

    Crafting the newly developed 94900-calibre movement

  • Watch Case

    An exquisite casket with an automatic watch winder

  • Night Sky Disk

    The night sky tailored specifically for you


The Portugieser Sidérale Scafusia is the most exclusive and complicated mechanical watch ever made by IWC. It took the project team at IWC Schaffhausen 10 years to develop and build this spectacular masterpiece. The dial, in the style of a classic Portugieser, features a constant-force tourbillon together with displays for the 96-hour power reserve and sidereal time. This deviates from normal solar time by just under four minutes each day and, among other things, is needed if we wish to find the same star each night in the same position. The reverse side of the Portugieser Sidérale Scafusia is a fabulous astrolabe calculated precisely to reflect the owner’s wishes. From a previously defined location, the rotating night-sky disc shows more than 500 stars and constellations with such detail and precision that it would quicken the pulse of any astronomer. Making the necessary allowances for summer time and winter time, the watch also displays the times of sunrise and sunset, sidereal time and a perpetual calendar with the leap years. In view of the enormous amount of work involved and the more than 200 individual configurations possible, only a few watches are produced each year.

A Glimpse of the Features

  • SOLAR TIMEThe central hour and minute hands show standard time (or mean solar time).

  • Sidérale timeThe subdial at "12 o’clock" shows sidereal time (or star time), a time-keeping system used by astronomers, on a 24-hour display. The time illustrated here is 8.03 a.m. The sidereal time display deviates by just 11.5 seconds per year from real star time.

  • Constant-force tourbillon and seconds handThis completely new combination of tourbillon and constant-force mechanism guarantees a precise and even rate for a period of at least 48 hours. In constant-force mode, the seconds hand jumps once a second. After this, the drive switches to normal mode, which is recognizable from the fact that it advances at the rate of one-fifth of a second.

  • Power reserve displayFully wound, the watch has a 96-hour power reserve.

  • Celestial chartDisplay showing the stars in the night sky as seen from a specific point on the Earth’s surface. It is always calculated individually to the customer's instructions.

  • Horizon and geographical coordinatesThe night sky, currently visible from the geographical position requested by the customer (yellow coordinates), is shown within the yellow ellipse.

  • Perpetual calendarDisplay showing the number of the day of the year on two day counter discs (ordinal date), together with a leap year display. The illustration shows the 188th day in a leap year, in this case 8 July 2012.

  • Solar timeThe red arrow with the dot shows mean solar time on a 24-hour display. The time is read from the outer ring. A solar day is the time taken by the Sun to pass over the same meridian twice.

  • Sidérale timeThe yellow arrow with the star shows sidereal time on a 24-hour display. This is likewise read from the inner ring. A sidereal day is the time taken by a star to cross the same meridian twice.

  • Sunrise and sunsetThese are shown by two red triangle hands on the outer 24-hour ring during standard time. During daylight saving time (DST+1) one must add one hour.

  • Daytime, night-time and twilight displayDaytime, night-time and twilight are indicated by the darkening or lightening of the planisphere.

  • EclipticThe red circle projects the apparent orbit of the Sun in the course of a year on the celestial sphere.

  • Celestial equatorThe dashed grey circle indicates the celestial equator. It is a projection of the Earth’s equator on the celestial sphere and forms a circular plane that separates the northern and southern hemispheres.



On the rear side of the watch, the night sky disc reveals the full glory of the star-studded heavens. A location chosen by the customer provides the basis of the calculations for the celestial chart and the astronomical displays. Realistically, it is possible to show around 500 to 1,000 stars. The sky disc rotates in a clockwise or anticlockwise direction, depending on whether the chosen geographic location is in the northern or southern hemisphere. The horizon, identifiable as a yellow ellipse, shows the movements of the stars and the section of the sky currently visible in the real night sky above the chosen coordinates. These coordinates indicate the precise location for which the planisphere has been calculated. The red circle projects the apparent orbit of the Sun in the course of a year on the celestial sphere (ecliptic). The dashed grey circle indicates the celestial equator that separates the northern and southern hemispheres. The red arrow with the dot shows solar time on the outer ring of the 24-hour display while the yellow arrow with the star shows sidereal time, likewise on the inner ring. The two red triangle hands at the edge show the current sunrise and sunset times at the chosen location. The perpetual calendar displays the current date as the number of the day of the year (absolute day). The 1st of January, then, is day 1, the 31st of December day 365, or 366 in a leap year.

Twilight, Sunrise and Sunset

—The night sky disc on the back of the
watch changes throughout the day

View How It Works


  • Contact IWC

Make It
Your Own


As part of its special service, IWC Schaffhausen enables customers to personalize the Portugieser Sidérale Scafusia wristwatch with countless different combinations of features. Taken together, the choice of materials for the case, the five different colours for the dial, the various colours for the appliqués and straps and the material used for the straps, result in over 200 different design options. IWC is only too pleased to honour special requests in the interests of exclusivity.

The case is made of precious metals such as platinum, 18-carat white gold or 18-carat red gold, while the straps are manufactured from the finest alligator leather or equus-hide.

The Portugieser Sidérale Scafusia is personally presented to its new owner in a top-quality watch case. It contains a removable casket, covered in alligator leather, in which the watch can be safely stored. Integrated into the case is an automatic winder, which was developed especially for this watch with IWC’s engineers. It winds the watch independently once a day via the crown. The large celestial chart on the inside of the watch case lid is, like the watch’s own celestial chart, individually calculated.

94900-CALIBRE Movement


Front view Movement

The imposing constant-force tourbillon gives the viewer a fascinating inside view of the delicately balanced mechanism. The tourbillon’s cage and upper section are made of titanium. The rhodium-plated escape-wheel and nickel-silver stop-wheel bridge are painstakingly hand-chamfered.

Back view Movement

The brushed bottom plate is inlaid with the “Probus Scafusia” stamp – “Good, solid craftsmanship from Schaffhausen” – IWC’s official seal of quality first used in 1903. The retaining plate and power reserve plate are sandblasted and rhodium-plated.

Astronomical Module

The plate for the astronomical module is likewise made of blasted, rhodium-plated nickel silver. It holds all the displays and technical parts such as wheels, levers and bridges that are needed on the rear side.

reference 5041

The Portugieser Sidérale Scafusia is the first watch from IWC to feature a patented constant-force tourbillon together with many other complications and individually calculated astronomical displays. Every watch is made on special request and will be unmistakably unique.




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