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Tuesday, May 02, 2023


Eta Aquariid Meteor Shower 4-8 May, 2023

The north-eastern horizon as seen from Adelaide at 4:00 am ACST, the eta Aquariid radiant is marked with a starburst. Similar views will be seen elsewhere in Australia at the equivalent local time (click to embiggen). 

The eta Aquariid meteor shower, which is produced by the debris from Halley’s Comet, will peak on May 6. 
Unfortunately, the Full Moon occurs at the same time, and will significantly reduce rates being seen. There has been predictions we might have a higher rate this year, so it is worthwhile to look out on the weekend mornings of May 5, May 6 and May 7, from 3:00 AM to 5:00 AM local time Australia-wide, where people with dark skies should see a meteor around every six to eight minutes. 

Again the Full Moon will cause significant interference this year. When choosing a viewing location, find one that blocks ot direct views of the Moon. There s also a penumbral lunar eclipse on the 6th, but the subtle darkening will not be enough to make more meteors appear.

People in the suburbs should see a meteor around once every 8 minutes, and in the country about once every 6 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 4:00 am above). The radiant is close to Saturn, which makes a good reference point.

Weather prediction looks like cloud except for some sections of the est coast.

You may have read that this year the eta Aquariids have a predicted ZHR of 40 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 practice, 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? 

The table below gives predictions below for various towns, but they are only predictions and while based on average steam density there may be some differences year to year, but good rates were seen in previous years, and dark sky sites may possibly see one meteor every 6-8 minutes or so. There were many bright ones reported with persistent trains in 2014. People in the suburbs maybe will see less, but at least one every 8 minutes should be possible. 

Predicted meteor rates for selected towns (taken from NASA shower Flux estimator below). If your city is not on the list you can expect a meteor rate similar to the closest city to you in latitude.

TownMorning May 5 Morning May 6Morning May 7
Adelaide10 meteors/hr8 meteors/hr6 meteors/hr
Brisbane11 meteors/hr82 meteors/hr6 meteors/hr
Darwin12 meteors/hr9 meteors/hr6 meteors/hr
Perth11 meteors/hr8 meteors/hr6 meteors/hr
Melbourne10 meteors/hr8 meteors/hr6 meteors/hr
Hobart9 meteors/hr7 meteors/hr5 meteors/hr
Sydney11 meteors/hr8 meteors/hr6 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 northeast, Altair and Fomalhaut, and Saturn as the center of your field (again, see the spotter chart at 4:00 am above).

Be patient, although you should see an average of a meteor every 6 to 8 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 Saturn just next to the radiant.

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, or the internet explorer tab under Edge, now.

You need to choose 31 Eta Aquariids and remember to set the date to  5-6 or 7-8 May 2023 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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