III.5. Center

Here user should specify the origin of coordinate system (observer's position). In case of rectangular coordinates it can be center of any major planet or the Sun or any minor planet. Mark necessary origin in the list box. For spherical coordinates the origin of coordinate system can coincide only with the center of the Earth or with any point on the Earth surface. One can specify position of observer on the Earth in different ways:

a)by code of observatory in the list of observatories maintained by Minor Planet Center (see IX. Observatories).

b)by introducing name of observatory. Clicking on data field leads to appearance of the Observatories dialog box that gives opportunity to find the code of observatory by name or by its fragment.

c)by parallax constants (east longitude and projections of radius- vector of observatory on the Earth equatorial plane and on the rotational axis of the Earth, dxy and dz, correspondingly). Longitude must be expressed in degrees, dxy and dz — in parts of equatorial radius; see section IX. Observatories.

d)by geographical coordinates of observatory (east longitude and latitude) and height above see level. Longitude and latitude are expressed in degrees, height — in meters.

Spherical coordinates of the Earth are not calculated even though topocenter is taken for the origin of coordinate system.