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Monday, May 07, 2018


eta Aquarid Meteor Shower 7-9 May, 2018

Morning sky on Tuesday May 7 looking east as seen from Adelaide at 5:00 am local time in South Australia showing the eta Aquariid meteor shower radiant as a star burst. Similar views will be seen elsewhere at the equivalent local time (click to embiggen).
The eta Aquarid meteor shower peaks on the morning of 7 May in Australia, although better rates will be seen on the mornings of the 8th and 9th. as the Moon wanes.

The eta Aquariids meteor shower, the debris from Halleys comet, will peak on May 6-7 UT , which is  May 7-8 in Australia.  However, the best rates will be seen from Australia on the mornings of the 8th and 9th.

This year conditions are less than perfect for seeing the eta Aquarids, with the Moon heading towards last quarter and near the radiant. People in the suburbs should see a meteor around once every 6 minutes, and in the country about once every 3 minutes. The radiant of the shower is about five hand-spans up from the eastern horizon, and three hand-spans to the left of due east at 4 am (see spotter chart at 4 am above).

You may have read that this year the eta Aquariids have a predicted ZHR of 50 meteors. The figure ZHR is zenithal hourly rate. This is the number of meteors that a single observer would see per hour if the shower's "point of origin", or radiant, were at the zenith and the sky were dark enough for 6.5-magnitude stars to be visible to the naked eye.

In practise, you will never see this many meteors as the radiant will be some distance below the zenith. Also, unless you are out deep in the countryside, the darkness will be less than ideal. As well, this year there is substantial Moonlight interference, which will was out many meteors. How many are you likely to see in reality? I discuss this further down, lets talk about when to see them first.

Although the actual peak is on 6-7th, for Australia the best time to see the eta-Aquarids is in the early morning of the 7th, 8th and 9th. This year the waning Moon will interfere significantly.

How many will be seen on the 7th is not entirely clear (see prediction below, but they are only predictions), but good rates were seen in 2016, and dark sky sites may possibly see one meteor every six minutes or so. There were many bright ones reported with persistent trains in 2014. People in the suburbs may be will see less, but at least one every 10 minutes should be possible. Rates should be  much the same on the 8th and the 9th.

The radiant of the shower is about five hand-spans up from the eastern horizon, and three hand-spans to the left of due east at 4 am (see above for a spotter chart at 5 am). When looking, be sure to let your eyes adjust for at least 5 minutes so your eyes can be properly adapted to the dark. Don't look directly at the radiant site, because the meteors will often start their "burn" some distance from it, but around a handspan up or to the side. The best way to watch the Eta Aquariids is to let your eye rove around the entire patch of the sky above the north-east horizon, between the only two obvious bright stars in the north-east, Altair and Fomalhaut.

Be patient, although you should see an average of a meteor every six to ten minutes, a whole stretch of time can go by without a meteor, then a whole bunch turn up one after the other.

Make yourself comfortable, choose an observing site that has little to obstruct the eastern horizon, have a comfortable chair to sit in (a banana lounger is best), or blankets and pillows. Rug up against the cold.  A hot Thermos of something to drink and plenty of mosquito protection will complete your observing preparations. As well as meteors, keep an eye out for satellites (see Heavens Above for predictions from your site).

Use the NASA  meteor shower flux estimator for an estimate of what the shower will be like from your location (you may need to enter your longitude and latitude, surprisingly, while Adelaide and Brisbane are hard wired in, Sydney and Melbourne are not). See the image to the left for typical output. The peak is rather sharp.

Unfortunately, both Chrome and Firefox have changed their security settings to prevent plugins from running, and the flux estimator only runs under Internet Explorer now.

You need to choose 31 Eta Aquariids and remember to set the date to  7-8 or 8-9 May 2018 and turn off daylight saving time. You can follow the progress of the shower at the IMO live Aquariid site.

Cloud cover predictions can be found at SkippySky.
Here is the near-real time satellite view of the clouds (day and night) http://satview.bom.gov.au/


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