Planetarium parameters

  • Natural sky colors: Displays a blue sky when the Sun is above the horizon.

Note

The blue color of the sky is caused by the scattering of sunlight off the molecules of the atmosphere. This scattering, called Rayleigh scattering, is more effective at short wavelengths (the blue end of the visible spectrum). Therefore the light scattered down to the earth at a large angle with respect to the direction of the sun’s light is predominantly in the blue end of the spectrum.

  • Show a cloudy sky: just for the pleasure of seeing the stars through the clouds….
  • Night sky luminosity: if the sky background appears too dark on your computer, it is possible to correct this by acting on this parameter.
  • Enlargement of the Sun and the Moon: sets a multiplicative factor to make the Sun and Moon appear larger than they are in reality (4x by default)….

Note

in the planetarium mode, if we represent the Sun and the Moon with their real size, they appear very small… Why? Contrary to the impression one might get, the apparent diameter of the Full Moon is the same when it appears at the horizon and when it sails in the middle of the sky a little later in the night. Of course, the Full Moon does not always remain the same size over the course of the year, as our satellite moves away and gets closer to us by traversing its elliptical orbit. But over a single night, there is no significant change in its apparent diameter. However, our senses are generally misused by the connection between the Moon and our usual landmarks, such as trees or buildings on the horizon. Our brains often misinterpret this and we sincerely believe that the Moon is bigger on the horizon. To convince you that this is an illusion, I suggest you do some gymnastics. The goal is to change your usual reference points and force your brain to analyze the scene from another angle by looking at the rising of the Full Moon with your head down! You can hang the pig or lean forward, the result will be the same: the Full Moon will appear to you as small on the horizon as it appears in the middle of the sky.