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I started using the software that comes with Jean Meeus book Astronomical Algorithms. I am now using the updated code from naughter(dot)com/aa.html.

I am able to calculate the heliocentric longitude and latitude for an asteroid using the orbital elements. Below is for the asteroid Juno. I can't find any source code or instructions for converting the asteroid coordinates I calculated below to geocentric longitude and latitude. Can anyone recommend a method to find asteroid geocentric longitude and latitude? Thanks.

double Longitude = 0.0; //West Greenwich  
double Latitude  = 51.4826; //North Greenwich  
double TZOffSet = 0.0;


//Asteroid Juno Elements;   Using epoch J2000
CAAEllipticalObjectElements elements;  

//Calculation Julian Date  2017, 9, 25 
elements.JDEquinox = JD;   

elements.T = (JD - 2451545.0) / 36525.0;

//semi-major axis of the orbit
elements.a = 2.6700912;

//eccentricity of the orbit
elements.e = 0.25498122;

//inclination of the plane of the ecliptic
elements.i = 12.98211;

//Longitude of ascending node
elements.omega = 169.91138;

//longitude of perihelion
elements.w = 248.10807; 

//-------------------------------------------------------------------------
CAAEllipticalObjectDetails details = CAAElliptical::Calculate(JD, elements, true);

1) Heliocentric Ecliptic Longitude  = 215.6670202
2) Heliocentric Ecliptic Latitude = 9.377841131
3) True Geocentric RA = 13.90415220
4) True Geocentric Declination = -3.802673727
5) True Geocentric Distance = 4.136531368
6) True Geocentric Light Time = 0.0238906126
7) Astrometric Geocentric RA = 13.90397025
8) Astrometric Geocentric Declination = -3.80217202
9) Astrometric Geocentric Distance = 4.13653445
10) Astrometric Geocentric Light Time = 0.023890630
11) Elongation = 26.74464206
12) Phase Angle  = 7.928218201
//-------------------------------------------------------------------------
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This can be accomplished through the following steps :

  1. compute the position of the Earth in the same heliocentric frame,
  2. express both positions (Earth and asteroid) in heliocentric rectangular coordinates,
  3. change the origin of the frame to get the location of the asteroid in geocentric rectangular coordinates,
  4. convert the position of the asteroid in geocentric latitude and longitude.
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  • $\begingroup$ Thank You. When I get that setup in a few days I will post the source code. I hope that works. $\endgroup$ – homebase Sep 28 '17 at 17:47

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