Tidally Locked Moon Fix hack

This is not a script, this is a replacement for the ssystem_major.ini file.

For tidally locked moons (such as our own, Mars' moons, Galilean satellites, etc), the Prime Meridian (0° Longitude) is defined as the middle of the face of the moon that is facing the planet. As such if you were on such a moon at 0° Longitude and 0° Latitude the planet should be directly overhead. Well, more precisely depending on the moon's eccentricity and inclination, the planet should oscillate around a point directly overhead, this called Libration see https://en.wikipedia.org/wiki/Libration).

In Version 0.16.0 the Stellarium developers tried to add tilt and polar rotation to the moon's parameters. This didn't work as expected and pretty much every longitude on these moons is off. That is if you go to one of these moons to 0°Lat/0°long the moon's planet is not overhead (it may be a little off or not even above the horizon). Also in the case of Mars' Deimos and Uranus' major moons their osculations are more extreme than expected, and in Charon's case, Pluto is now seen to rise & set. 

What this replacement does.

By downloading and replacing the ssystem_major.ini with this one, the longitudes on the moons will be fix. For example

Example #1
Mars from Phobos at 0°Lat/0°Long
     

 
Without Fix: Mars is in the east and almost off screeen With Fix: Mars is correctly over head   

   

Example #2
Pluto from Charon at 0°Lat/0°Long

 
Without Fix: Pluto is seen to rise & set from Charon in the Southern Hemisphere. With Fix: Pluto is correctly always overhead  

     

Moons Fixed

Mars: Phobos(1), Deimos(2)

Jupiter: Metis, Adrastea, Amalthea, Thebe, Io, Europa, Ganymede, Callisto

Saturn: Pan, Atlas, Prometheus, Pandora, Epimetheus, Janus, Mimas(1), Enceladus, Tethys, Telesto, Calypso, Dione, Helene, Rhea, Titan, Iapetus

Uranus: Cordelia, Ophelia, Cressida, Desdemona, Juliet, Miranda(2), Ariel(2), Umbriel(2), Titania(2) and Oberon(2)

Neptune: Naiad, Thalassa, Despina, Galatea, Larissa, Proteus, Triton

Pluto: Charon(2)(3)

(1) Phobos and Mimas good for a few decades before they start to drift. This is due to a different unrelated bug with no fix yet.

(2) Also fixes Deimos, Major Uranus' Moons, and Charon's host planet's extreme North- South oscillations.    

(3) Charon - Stops rotating so Pluto is always above. Note: From Pluto, Charon will be stationary in the sky but still rotating in place (working on fix). 

 

Download ssystem_major.ini fix for 0.16.1

Instructions

1) Right Click "Download ssystem_major.ini fix for 0.16.1" link above

2) Click "Save Link As" or "Save Target As"

3) Using Windows save file in C:\Program Files (x86)\Stellarium\data  

4) Overwrite Existing file  (Though I recommend making a backup of original)

5) Open or Restart Stellarium

Moons shall be fixed