FW Editor: Can you tell us a few things about yourself? Do you have a passion for sundials and astronomy?
Francois BLATEYRON: I started as an amateur astronomer when I was student and when later I became a professional software programmer, I decided to combine my skills in programmation with my passion for astronomy, and started to develop celestial mechanics equations and astronomical algorithms. A good application is the trajectory of sun that is the basis of sundial theory.

FW Editor: What determinate you to develop such a complex application like Shadows? It was hard to create something like that all by yourself?
Francois BLATEYRON: Shadows is a complex application inside, but very easy to use. I always wanted to make complicated things easy for most users. With Shadows, you can design a sundial without knowing a single equation. It is used sometimes in schools for projects with children below 10. The program is able draw and print the layout of the sundial, and you can use it to realize a real sundial on wood, stone or metal. From the first version of Shadows in 1997, I decided to offer it online on my web site and a lot of enthusiasts around the world encouraged me to further develop it. These users also made translations of the user interface which is now available in 13 languages.

FW Editor: Can you tell us a few things about the differences between Shadows and Shadows Pro? Which package would you recommend for a common computer user?
Francois BLATEYRON: Shadows is the first level of the application. It is free and can be downloaded by anyone. It offers a lot of features for creating simple sundials. Shadows Pro is the top level that contains advanced features and offers also astrolabes. This high end level requires a fee of 50 euros. Most users buy Shadows Pro because it is not expensive and they can enjoy all features and discover much more than they expected initially.

FW Editor: Who can use Shadows? Is Shadows for astronomy enthusiasts only or everyone can enjoy this amazing software?
Francois BLATEYRON: Shadows is used by very different users. Some are interested by astronomy and sundials. Some just want to create a sundial for their house or garden but they do not know anything about the technical background. Others are interested by the philosophy of mottoes. The nice thing with Shadows is that it allows non-technical people to discover gnomonics - the science of sundials - without requiring any knowledge. Others are interested by astrolabes. Shadows Pro is the only shareware application able to draw and use astrolabes on screen.

FW Editor: Can you tell us a few things about the equations of time and time graphs available in Shadows?
Francois BLATEYRON: The equation of time tells us the difference between solar time and mean time (time given by your watch). It varies like a double sine wave of plus or minus 15 minutes during the year and it is responsible of the 8-shape curve that we see sometimes on sundials. Shadows draws various graphs of the equation of time and provides tables with numerical values.

FW Editor: Shadows allows the user to create various types of sundials. Can you tell us a bit more about that?
Francois BLATEYRON: Shadows can create classical sundials with a polar style, of any reclination or orientation. It offers also more specific sundials such as analemmatic sundials that are made with a large ellipse, bifilar sundials that have two crossing threads instead of a style, and cylindrical sundials such as the famous shepherd's dial. I have to add 3 types of astrolabes, although they are not sundials.