Creating a Chart

The goal for this tutorial is to help you create a Chart for a specific date and location. To build a Chart it will be necessary to define:

• the date and time, given by the Datetime object.
• the geographic position, given by the GeoPos object.

Datetime

The Datetime class represents a specific moment in time given by a Date, a Time, an UTC offset and the calendar type. It assumes, by default, the Gregorian calendar.

To create a Datetime object, we must first import it. Here’s an example that creates a Datetime object for the 13th of March of 2015 at 5pm, assuming UTC+0:

>>> from flatlib.datetime import Datetime
>>> date = Datetime('2015/03/13', '17:00', '+00:00')
>>> date.jd
2457095.2083333335

The jd attribute (as in date.jd) returns the Julian Date.

The time and UTC offset parameters are optional, and the arguments could be given as lists instead of strings. Some alternative ways to build the same date object are:

>>> # No UTC Offset argument
>>> date = Datetime('2015/03/13', '17:00')
>>> date.jd
2457095.2083333335

>>> # Build date with date and time lists
>>> date = Datetime([2015,3,13], ['+',17,0,0])
>>> date.jd
2457095.2083333335

The Datetime object provides properties and functions which may be useful for some situations:

>>> # Print date, time and offset
>>> print(date.date)
<2015/03/13>
>>> print(date.time)
<17:00:00>
>>> print(date.utcoffset)
<00:00:00>

>>> # Other properties
>>> date.date.dayofweek()
5   # 5 is Friday
>>> date.time.toList()
['+', 17, 0, 0]

GeoPos

The GeoPos class represents a geographic position on Earth given by a latitude and longitude. To create a GeoPos object, we must first import the class definition and instantiate an object. Here’s an example:

>>> from flatlib.geopos import GeoPos
>>> pos = GeoPos('38n32', '8w54')
>>> pos.lat
38.53333333333333
>>> pos.lon
-8.9

When building the geopos object, the first parameter must be the latitude and the second the longitude. The latitude and longitude properties can be accessed directly (using pos.lat and pos.lon). Northern latitudes and eastern longitudes have positive values, while southern latitudes and western longitudes have negative values.

Alternative ways to build a Geopos object can be:

>>> # Using angle strings
>>> pos = GeoPos('+38:32','-8:54')
>>> pos.lat, pos.lon
(38.53333333333333, -8.9)

>>> # Using angle lists
>>> pos = GeoPos(['+',38,32], ['-',8,54])
>>> pos.lat, pos.lon
(38.53333333333333, -8.9)

>>> # Using the float values
>>> pos = GeoPos(38.53333333333333, -8.9)
>>> pos.lat, pos.lon
(38.53333333333333, -8.9)

Chart

The Chart class represents an Astrology chart for a specific datetime and geographic position. To create a chart object, we must create the Datetime and GeoPos objects and pass them as arguments to the Chart:

>>> # Set datetime and position
>>> from flatlib.datetime import Datetime
>>> from flatlib.geopos import GeoPos
>>> date = Datetime('2015/03/13', '17:00', '+00:00')
>>> pos = GeoPos('38n32', '8w54')

>>> # Finally create the chart
>>> from flatlib.chart import Chart
>>> chart = Chart(date, pos)

By default, the chart will include only the Traditional planets (Sun to Saturn, including Pars Fortuna and the Moon nodes) and the Alcabitius house system. To create a chart with other parameters, we must first import the flatlib.const module (where some things are defined) and pass some arguments in the object constructor:

>>> from flatlib import const

>>> # Build a chart with Regiomontanus houses
>>> chart = Chart(date, pos, hsys=const.HOUSES_REGIOMONTANUS)

>>> # Build a chart including modern planets
>>> chart = Chart(date, pos, IDs=const.LIST_OBJECTS)

>>> # Build a chart with only the Sun and Moon
>>> chart = Chart(date, pos, IDs=[const.SUN, const.MOON])

In the next tutorials it will be shown how we can access the chart’s properties, including objects, houses and angles.