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Mon, 06 Oct 2014 - When do the Orionids start and end?

The Orionid meteor shower peaks each year around Oct 20-23.
Richard Fleet's composite image showing Orionids imaged during the night of 2013 Oct 23-24.
 
However, when does it start and end?
 
Older meteor shower listings gave the activity period as Oct 17-26, but the published date range has expanded in recent years:
 
SPA MS :           Oct 14 – 31
BAA MS :           Oct 16 – 30           
IMO Calendar :   Oct 2 – Nov 7
AMS :                Oct 4 – Nov 14
    
In addition, Robert Lunsford’s weekly meteor activity previews, published via the IMOnews and meteorobs mailing lists, have the Orionids active by early September.
 
It is not the case that the Orionid meteor shower now lasts for longer.
 
In the past, meteors seen outside of the traditional Orionid activity dates would usually be dismissed as being sporadic meteors that, by chance, just happened to line up with the Orionid radiant.
 
In recent years, however, the rise in video monitoring of meteor showers has now made it possible, using triangulation, to calculate the atmospheric trajectory of more Orionid meteors and then work backwards to determine the former solar system orbit of the particles that produced them. 
 
This has made it possible to positively identify Orionid activity outside of the traditional activity dates. A particle that had an orbit with parameters similar to those of the orbit of the parent comet 1P/Halley, may well get classified as an Orionid.
 
But this introduces possible problems ...
 
- We need to remember that below a certain activity level a meteor shower will not be apparent to a visual observer.
 
- We also need to bear in mind that most Sky Diary authors are not meteor observers. Consequently, they are likely to merely quote activity date ranges that they have seen listed elsewhere.
 
Meteor groups clearly need to bear these factors in mind when listing date ranges. What we need to avoid is a situation whereby potential meteor observers are given misleading information about likely observed Orionid rates and are subsequently left feeling disappointed and misled
 
So, if you are a visual observer, then you are unlikely to spot any Orionids before the third week of October or after the end of October. Orionid activity does occur outside of this date range, but rates are very low and meteors can only be confirmed to be Orionids via imaging and triangulation.
 
For futher information about the 2014 Orionid meteor shower, see our guide at: 
http://www.popastro.com/meteor/activity/activity.php?id_pag=231
 

Added by: Tracie Heywood