Progressions and Directions – some notes, comparisons and details
AC = AstroConnexions. SA = Solar Arc, RA = Right Ascension, Long = Longitude, MC = Midheaven, Asc = Ascendant
Solar Fire, Windows astrology software. Astro Gold, iOS astrology software.
RA or Long – Naibod
Tropical and sidereal are calculated by AC in the same way Solar Fire, Astro Gold iOS, and astro.com calculate these progressions. Note that astro.com does not calculate sec. prog. in long.
In Solar Fire the option for sec. prog. in RA is “Chart Angle Progression: Naibod in RA”.
MC by Solar arc – this is similar to the setting in astro,com (which is used with sec prog. in RA by AC and astro.com):
Solar Arc directions
AC calculates the difference between the natal Sun in long and the progressed Sun in long which gives the Solar Arc. This arc is added to the ramc of the natal MC to give the progressed MC in RA. Then the ecliptic longitude of the progressed MC and corresponding Asc is derived.
astro,com gets the same results as AC. Astro gold iOS calculates the Asc differently. It adds the SA arc to the natal Asc. This gives a different Asc directed degree from AC and astro.com
The SA arc is added to the natal planetary positions to get the SA progressed planetary positions. Parts, eg Part of fortune are calculated from the new progressed positions.
Solar Arc declinations
are calculated in a similar manner to astro.com and not like Solar Fire.
All other solar arc calculations/results in longitude are the same for astro.com and Solar Fire:
Directed planetary/points, House Cusps.
AC calculates the difference between the natal Sun in RA and the progressed Sun in RA – Solar Arc. This arc is added to the ramc of the natal MC to give the progressed MC in RA. Then the ecliptic longitude of the progressed MC and corresponding Asc is derived.
Astro.com does not include SA by RA. Note that Astro Gold iOS calculates the Asc and MC differently than AC.
AC adds the Solar Arc in RA to the natal planetary positions to get the SA progressed planetary positions for AC. Astro Gold iOS/Solar Fire does not do this.
Parts, eg Part of fortune, are calculated from the new progressed positions.
Tropical and/or sidereal:
AC recommends using Solar Arc in Long, and Secondary Progressions in RA.