# [Orekit Users] Right ascension and declination

• To: orekit-users@orekit.org
• Subject: [Orekit Users] Right ascension and declination
• From: Philippe Demoulin <Philippe.Demoulin@aeronomie.be>
• Date: Thu, 7 Dec 2017 12:00:45 +0100
• User-agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0

```Hi everybody,

```
I am completely new to Orekit, and I followed the 3-day course at CS last week (thanks Luc !). I just started with a small program to compute the right ascension and declination of Jupiter :
```
AbsoluteDate date = new AbsoluteDate(2017, 12, 6, 10, 17, 0.0,
TimeScalesFactory.getUTC());

CelestialBody body   = CelestialBodyFactory.getJupiter() ;
Frame eme2000 = FramesFactory.getEME2000();

```
Vector3D bodyInEME2000 = body.getPVCoordinates(date, eme2000).getPosition();
```
double rightAscension = bodyInEME2000.getAlpha() ;
```
if (rightAscension < 0) rightAscension = rightAscension + 2. * FastMath.PI ;
```           double declination = bodyInEME2000.getDelta() ;
```
System.out.format(Locale.US, "At %s UTC, %s RA = %10.5f°, DEC = %10.5f° %n", date, body.getName(), FastMath.toDegrees(rightAscension),
```                   FastMath.toDegrees(declination)) ;

The output of this program is :
```
"At 2017-12-06T10:17:00.000 UTC, Jupiter RA = 219.81633°, DEC = -14.44226°"
```
```
Computing the same parameters with the JPL Horizons system (https://ssd.jpl.nasa.gov/horizons.cgi) gives RA = 219.81392° and DEC = -14.44186°, i.e. a difference of 8.7" in RA and -1.4" in DEC.
```
Do you have any idea of the reason of these different answers ?