Finding planets

  • The headmap sphaeric web page has a simple geometrical method for finding rough positions of the planets based on using concentric circles to represent the orbit of the planet and of the earth.

I’ll re-work this a little minus the ideology.

Note added 27th Feb : errors prove large for Mars. The smaller signal is the declination error and the larger is Right Ascension error, both differences in degrees. The peak error in RA is getting on for two hours of time!

error using circular orbit for Mars

Jupiter has an orbit that is much larger than Earth’s so the heliocentric and geocentric longitudes for Jupiter are not that different. Mars and Earth have orbits that are much closer in size – so the ‘parallax’ when you sit on Earth instead of the Sun changes a lot.

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