See planet Mercury near Spica

See if you can spot Mercury and Spica in daylight on 22 September 2020 at 14:30 BST (13:30 UT).

Mercury and Spica, as they appear through a telescope eyepiece at x25 on 22 September at 14:30 BST (13:30 UT). Credit: Pete Lawrence

On 22 September 2020, mag. 0.0 Mercury lies due south at 14:30 BST (13:30 UT), attaining an altitude of 26˚ from the centre of the UK. At this time, it’s 0.3˚ northeast of mag. +1.0 Spica (Alpha (α) Virginis).

Advertisement

Despite being daylight, given clear skies it may still be possible to see both planet and star.

The easiest way to locate them in daylight is to offset from another astronomical object, in this case the Sun.

Please note: precautions must be used in order to do this as observing the Sun without proper equipment is incredibly dangerous. If you’re not sure what you’re doing, don’t attempt it.

A telescope on an aligned equatorial mount with setting circles can be used. The telescope must be filtered using a full aperture certified solar filter. Finders must be capped or filtered too.

Take care not to look at the Sun directly, and use a solar filter. Credit: Dave Eagle
Only a telescope with a proper solar filter should be used to view Mercury and Spica. Credit: Dave Eagle

Centre on the Sun and set the setting circles to the Sun’s co-ordinates, then offset to Mercury.

Ensure the scope isn’t pointing at the Sun before removing the filters or caps. As a double-check, the scope should be pointing east (left) of the Sun.

At 14:30 BST on 22 September the Sun’s co-ordinates are RA 11h 59m 00s, dec. +00˚ 06 minutes 36 seconds. The RA of Mercury will be 13h 26m 18s, dec. –10˚ 59 minutes 42 seconds.

Apps or planetarium programs such as Stellarium can be used to give the positions at other times of the day.

Advertisement

Pete Lawrence is an experienced astronomer and a co-host of The Sky at Night. This guide originally appeared in the September issue of BBC Sky at Night Magazine.