High!

While waiting for help with the rail segments connection problem, I 
reactivated a very old project put to hibernation back in 1999: a 
full-fledged POV Solar System, this time with astronomically correct 
elliptical orbits of planets and moons and a procedural starry 
sky_sphere gleaned from star data from a German astronomical atlas 
("Karkoschka"), as I found a promising tutorial on computing planetary 
positions on the website of a Swedish amateur astronomer
( http://www.stjarnhimlen.se/comp/tutorial.html )

I programmed several camera modes, one of them with the camera pointing 
towards a customizable location stated in geographical coordinates on 
Earth. As long I left my Earth sphere standing upright in space, this 
works fine - but how do I correct the camera's orientation for Earth's 
axial tilt (rotate <23.4333, 0, 0>?

I quickly understood that the tilt angle multiplied with the sine of the 
  longitude (with western longitudes being positive, eastern ones 
negative) had to be added to/subtracted from the original latitude - but 
how is the longitude adjusted afterwards?

See you in Khyberspace!

Yadgar

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