Some chart points have different methods of calculation. For instance, while most of the time planets are calculated geocentrically, the Parallax Moon option will calculate the Moon topocentrically. This page contains the different types of calculation options available in LUNA for various chart points.

## Parallax Moon (Locus)

Planetary positions are calculated from a geocentric perspective. The “Parallax Moon” option calculates the Moon from a topocentric (i.e. Earth surface) perspective. This setting can change the position of the Moon by up to about one (1) degree.

Note that LUNA does not take the location’s altitude into account when calculating the Parallax Moon. This can result in a difference of about two (2) arc seconds when at an altitude of 3,000 meters.

## Lot/Part Calculations

LUNA can calculate two (2) of the Lots/Parts:

- Lot/Part of Fortune
- Lot/Part of Spirit

These are calculated points based on a combination of the Sun, Moon and Ascendant of the chart. You can indicate which calculation method you prefer by selecting from the options provided:

### Respect Diurnal/Nocturnal (sect)

This option will take the sect of the chart into consideration when calculating these points. Thus for a diurnal (daytime) chart, the standard equation for Fortune is used:

`Ascendant + Moon - Sun`

For a nocturnal (nighttime) chart, however, the inverse of this equation is used:

`Ascendant + Sun - Moon`

*The same calculation rules apply to Spirit also.*

### Ignore Sect (fixed)

This option will ignore the sect of the chart and use the standard equation for both Fortune and Spirit at all times.

## Planetary Nodes

When viewing planetary nodes on your charts, LUNA can calculate them from a geocentric or heliocentric position. Note that the north and south heliocentric planetary nodes are always 180° apart from one another.

However, geocentric planetary nodes are not necessarily separated by this same distance. This is because the nodes represent the planet’s orbit as it intersects the ecliptic, which from Earth’s perspective does not necessarily occur at opposite points of the zodiac.