Basically it frames a small section of the night sky

Sidereal time is displayed in a 24 hour format as is known as the true earth time in terms of a rotational standpoint - different that the standard time and solar time. These days sidereal time is used by astronomers, and people who buy watches that contain this complication. Like an equation of time indicator - this complication is more emotional than useful to the majority of people.Things get a lot more complex on the back of the watch where the astronomical data is displayed. Here you will also find one of the world's most diminutive perpetual calendar displays. The large astrological chart is based on a specific sky location the customer must choose. . IWC claims that the chart can display the actual position of about 500 - 1000 stars. The chart moves to represent how the view of the sky changes from the perspective of someone standing on earth. The chart and hands around the chart further indicator sunset/sunrise data, sidereal time, solar time, and day/night indicator. It is all very complex, tiny, and awesome.Around the periphery of the star chart is the perpetual calendar. See it now at the top? This perpetual calendar is a bit different than you might be used to as it only displays the leap year indicator and a count of what number day it is in the year (1 - 365). I think that is all pretty cool - but of course all of this info is only viewable when you take the watch off. No doubt that the calibre 94900 is extremely impressive on all accords.If you are familiar with other complicated IWC watches built on the Portuguese platform you'll instantly recognize this watch. The case is 46mm wide by 17.5mm thick. You can get it in 18k white or red gold, and also in platinum. If you want something special, IWC will likely do that as well given that each piece is made to order. In terms of customization, IWC claims that there are over 200 combinations possible. This include case materials, polishes, straps, and dials. Don't forget that you'll be asked to choose what part of the sky you want on the back of the watch. Oh, and I love this statement (so Swiss), "IWC is only too pleased to honor special requests in the interests of exclusivity."As a new brand marquee and super-complex watch for the high-end market the IWC Portuguese Sidérale Scafusia is a satisfying creation. IWC has a micro-site with details and a nice presentation on it here. This watch will help boost brand confidence and appeal in developing markets that are just starting to really learn about the brand. While I like this watch a lot, I know it is a separate creature so it does not really change the way I feel about other IWC pieces (which I, for the most part, already like anyways). Ordering an IWC Portuguese Sidérale Scafusia will set you back about 750,000 Swiss Francs - and if you want one in the next few years you better put in your order soon.Tech Specs from IWC:Portuguese Sidérale Scafusia Watch Ref. 5041FeaturesMechanical movement, new balance with two adjustment cams and two adjustment weights, Breguet spring, two barrels, constant power tourbillonDial side displays 24-hour display (sidereal time), sidereal time and solar time can be set separately, power reserve displayRear 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 dayMovementCalibre 94900Frequency 18,000 A/ h / 2.5 HzJewels 56Power reserve 4 days (96 h)Winding hand-woundWatchMaterials Case material as specified by customer (e.g. platinum or red gold)Strap as specified by customer with IWC folding claspGlass Sapphire, convex, antireflective coating on both sidesBack see-through sapphire-glass backWater-resistant 3 barDiameter 46 mmHeight 17.5 mm