2018 Orionids

The best of the early/mid autumn meteor showers, though moonlight will interfere badly in 2018.

Main Activity Dates Oct 14 – 31
Peak Rates Oct 21 – 23
Peak ZHR 20 – 25
Best Observed Rates Late in the nights of Oct 21 – 23
Visibility each night (UK) Only after the radiant rises at ~ 21h UT
Moonlight issues at Maximum Major: full Moon is on Oct 24

The Orionid meteor shower arises from the Earth’s pre-perihelion encounter with the meteor stream of comet 1P/Halley.

The Orionids usually produce good observed rates, especially in the later part of the night. Although some meteor shower listings give a start date in early October, Orionid rates remain very low until the third week of the month. There is no sharp maximum and good rates should be seen during Oct 21-23. The peak ZHR will probably be about 20 this year (the actual observed hourly rate will, of course, depend on the darkness of your observing site). Strong Orionid activity (ZHRs ~35-80) occurred in the years 2006-2010 inclusive, when such rates persisted for two or more nights at these levels. However, no repeat is expected this time, but surprises can occur. Orionid meteors are typically swift moving, with good persistent trains.

Bear in mind that the Orionid radiant doesn’t rise until around 21h UT (10pm BST) and so no Orionids will be seen before this time.

With full Moon occurring on Oct 24, the peak of activity will coincide with a bright gibbous Moon which will drown out the fainter meteors. However, it will be some distance from the radiant so observing will be possible if you keep your back to the Moon.

The motion of the Orionid radiant between Oct 10 and Oct 30 is shown on the chart below – note that the radiant lies closer to Gemini than to the main pattern of Orion.

Orionid radiant
Orionid radiant

Some activity from the Taurid meteor shower will also be visible during Orionid meteor watches.