Time span

Use the Time span dialog to specify the time span of the ephemeris calculation. Select Ephemeris->Time span from the main menu or press Alt+T . The Time span dialog appears.

Select the type of time span definition from the Define by list. There are three types of time span specification:

1. Start time, Step size, Number of steps  The time span of ephemeris calculation is defined by a starting time, the step size and the number of steps ahead and back from the starting time. The start time may be specified as a calendar date and optionally time (YYYY-MM-DD [HH:MM:SS]), as a Julian day number or as numerical expressions. See time specification for more information and examples. Click the  button to specify time value by use of  the Astronomical Event Calculator . Click the  button to specify time value by use of the Calendar conversion tool. The step size determines the difference in time between succeeding ephemeris calculations and may be expressed as a statement of days, hours, minutes, and seconds ([DDd] HH:MM[:SS]), as a decimal number of days, or as a numerical expression. See step size specification below for more information and examples. The number of steps ahead and steps back determines the number of ephemeris data to be calculated. The calculation can be performed both after (ahead) and/or before (back) the start time. A maximum of 1024 values are accepted in each direction; the maximum total number of values which can be calculated is 2049 (1024 + 1 + 1024). The resulting dates of the calculations must range between -2999 and +3000.
2. Start time, End time, Step size The time span of ephemeris calculation is defined by the start time, the end time, and the step size. The start time and end time may be specified as calendar dates and optionally times (YYYY-MM-DD [HH:MM:SS]), as Julian day numbers or as numerical expressions. See time specification below for more information and examples. Click the  buttons to specify time values by use of  the Astronomical Event Calculator. Click the  buttons to specify time values by use of the Calendar conversion tool. The step size determines the difference in time between succeeding ephemeris calculations and may be expressed as a statement of days, hours, minutes, and seconds ([DDd] HH:MM[:SS]), as a decimal number of days, or as a numerical expression. See step size specification below for more information and examples. The number of ephemeris data to be calculated is determined by the formula (JD1-JD0)/StepSize (JD1: end time, JD0: start time, StepSize: step size). A maximum of 1024 values is accepted.
3. Discrete time values The time span of ephemeris calculation is defined by a list of discrete time statements, calendar dates and optionally times (YYYY-MM-DD [HH:MM:SS]), as Julian day numbers or as numerical expressions. See time specification below for more information and examples. Click the  button to import a list of time values from the Astronomical Event Calculator. While types 1 and 2 (see above) of time span specification only allows ephemeris calculations with 'equi-distant' step sizes, this type of time span specification allows variable steps sizes (intervals) too. In the case of variable step sizes the minimum and maximum step size is shown in the status bar of the main window. The number of ephemeris data to be calculated is determined by the number of values in the list. A maximum of 1024 values is accepted.