Astronomical events of the month: how to observe them

The month's events page looks like a list of dates and terms that is easy to mistake for desk calculations. In fact almost all of it can be seen without a telescope, if you know where to look.

What an astronomical event is

An event is a moment when the arrangement of bodies in the sky takes on a special character. It is defined by the difference in their ecliptic longitudes, which is why every angle in such a list is measured in degrees along the ecliptic.

The main types

Conjunction — the bodies have close longitudes and look adjacent. The most striking event for an unaided observer, unless the Sun happens to be nearby: Mercury's conjunction with the Sun is invisible, while a conjunction of Jupiter and Saturn is a fine sight.

Opposition — the bodies sit on opposite sides of the sky, about 180° apart in longitude. A planet at opposition is visible all night, rising at sunset and setting at dawn. The best time of year to observe it.

Quadrature — about 90° apart. The planet is visible mostly at night but not all of it: it rises around midnight and sets around midday.

Meteor shower — not a positional event but a lot of meteors in a short period. The peak is normalised for activity; at our latitudes a radiant above 55° is usually hard to see because of the atmosphere.

What is visible without optics

The naked eye shows: planetary positions, bright meteors, the phases of the Moon, the rising and setting of all celestial bodies, and faint nebulae in a dark sky. It does not show: moons, Saturn's rings, detail on the solar disc, and most distant galaxies.

How to use the data

Each event in the table carries a date, a time, an angular separation and — far more useful in practice — an azimuth and altitude for your city at the moment of the event. Find the point in the sky with that altitude in that direction and the event will nearly always lie within ten degrees of it, which is inside your field of view with no telescope at all.