Search results
Results From The WOW.Com Content Network
Right ascension (blue) and declination (green) as seen from outside the celestial sphere Various hour angles are depicted here. The symbol ♈︎ marks the March equinox direction. Assuming the day of the year is the March equinox: the Sun lies toward the grey arrow, the star marked by a green arrow will appear to rise somewhere in the east ...
In this case, the longitude is also called the right ascension of the ascending node (RAAN). The angle is measured eastwards (or, as seen from the north, counterclockwise) from the FPA to the node. [2] [3] An alternative is the local time of the ascending node (LTAN), based on the local mean time at which the spacecraft crosses the equator.
Alternatively to right ascension, hour angle (abbreviated HA or LHA, local hour angle), a left-handed system, measures the angular distance of an object westward along the celestial equator from the observer's meridian to the hour circle passing through the object. Unlike right ascension, hour angle is always increasing with the rotation of Earth.
Angles in the hours ( h), minutes ( m), and seconds ( s) of time measure must be converted to decimal degrees or radians before calculations are performed. 1 h = 15°; 1 m = 15′; 1 s = 15″ Angles greater than 360° (2 π ) or less than 0° may need to be reduced to the range 0°−360° (0–2 π ) depending upon the particular calculating ...
The local hour angle (LHA) of an object in the observer's sky is = or = + where LHA object is the local hour angle of the object, LST is the local sidereal time, is the object's right ascension, GST is Greenwich sidereal time and is the observer's longitude (positive east from the prime meridian). [3]
If, instead of measuring from and along the horizon, the angles are measured from and along the celestial equator, the angles are called right ascension if referenced to the Vernal Equinox, or hour angle if referenced to the celestial meridian.
The declination angle is measured north (positive) or south (negative) of the celestial equator, along the hour circle passing through the point in question. [1] Right ascension and declination as seen on the inside of the celestial sphere.
This quantity is also sometimes referred to as the right ascension of the ascending node (or RAAN). Argument of periapsis ( ω ) — defines the orientation of the ellipse in the orbital plane, as an angle measured from the ascending node to the periapsis (the closest point the satellite body comes to the primary body around which it orbits ...