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Sunday, May 05, 2019

 

Reminder: Eta Aqaurid Meteor Shower 7-9 May, 2019

Morning sky on Tuesday, May 7 looking east as seen from Adelaide at 4:00 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).

Just a reminder that the eta Aquarid meteor shower peaks on the late evening/early morning of  6-7 May in Australia, although better rates will be seen on the mornings of the 7th, 8th and 9th. 

There has been some confusing about the actual peak, ads the International Meteor organisations  calendar website says 5-6, while their PDF calendar says peaking on May 6 14:00 UT, and their viewing website says May 7. 

For the purposes of of viewing I will take the PDF calendars reported peak on May 6 14:00 UT, which is  (just) May 7 in eastern Australia as the real peak.  As the meteor radiant does not rise until around 2 am, and is not at a reasonable hight until 3:30 am for Australians our best viewing times are in the mornings after the actual peak.

However, the peak is really broad and viewing from the 6-9 will give you decent rates (see table below). Based on the NASA meteor flux program (see below) and my own excel spreadsheet using the Jennisken's eta Aquarid stream parameters the best rates will be seen from Australia on the mornings of the 8th and 9th (see table below, but the 7th is very worth while too, fiddling with the parameters a bit gives 7th 8th as the best but as you can see the rate difference between the nights is marginal).

This year conditions are perfect for seeing the eta Aquarids, with the Moon just after new and in the evening skies. 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).

Weather prediction looks good with clear mornings for most of Australia (except the bit where I live)

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 was 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. How many are you likely to see in reality? I discuss this further down, let's talk about when to see them first.

Although as I said above 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, with the best rates between around 4-5 am (see table below).

How many will be seen on the 7th - 9th  is not entirely clear (see predictions below for various towns, but they are only predictions), but good rates were seen in 2016, and dark sky sites may possibly see one meteor every 2-3 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 6 minutes should be possible. 

Predicted meteor rates for selected towns (taken from NASA shower Flux estimator below)


TownMorning May 7 Morning May 8Morning May 9
Adelaide16 meteors/hr20 meteors/hr18 meteors/hr
Brisbane17 meteors/hr21 meteors/hr19 meteors/hr
Darwin18 meteors/hr22 meteors/hr20 meteors/hr
Perth17 meteors/hr20 meteors/hr18 meteors/hr
Melbourne16 meteors/hr19 meteors/hr17 meteors/hr
Hobart15 meteors/hr18 meteors/hr16 meteors/hr

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 hand-span 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 3 to 6 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).  The Milky way will arch above you, with Jupiter and Saturn to the north and Venus and Mercury will grace the morning skies as twilight begins.



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 2019 and turn off daylight saving time. You can follow the progress of the shower at the IMO live Aquariid site.

Guides for taking meteor photos are here and here.

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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