Mangala gochar in 2018

Gochar means the movement of the grahas: each moves on through the zodiac, and when it crosses from one rasi into the next, that is its sign change (sankramana). This page only says which graha is where, and when. In the classical method gochar is read by counting from a person’s natal Moon sign; to see today’s sky against your own chart, open the transits tool.

Seen from the Earth, Mars, Mercury, Jupiter, Venus and Saturn now and then appear to move backward for a while. That is retrograde motion; the instant the graha stops and turns is a station, and moving forward again is turning direct. It is an effect of the Earth and the planet moving on their orbits at different speeds. The Sun and Moon are never retrograde; Rahu and Ketu (mean) always move backward.

A graha very close to the Sun is lost in its glare; the texts call it asta (set), and its reappearance udaya (rising). The Surya Siddhanta gives a distance limit for each graha. The limits used here: Mangala 17°, Budha 14° (12° when retrograde), Guru 11°, Shukra 10° (8° when retrograde), Shani 15°. Almanacs leave out the asta periods of Guru and Shukra when choosing times for samskaras such as weddings.

Indian almanacs count the rasis against the stars (nirayana). Western (tropical) signs run about 24° ahead, so the dates printed there are about three weeks earlier than these. The ayanamsa used here is Lahiri.

Each graha’s apparent geocentric position from NASA JPL’s DE421 ephemeris, less the Lahiri ayanamsa. The instants of crossing a rasi edge, of zero speed and of reaching the asta limit are found by bisection to under a second. Small differences in ayanamsa can move a slow graha’s time (Shani above all) by a few hours against other almanacs.