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Tuesday, July 26, 2016


Southern Delta Aquariid Meteor Shower 29-31 July, 2016

Evening sky looking east from Adelaide at 2 am local time on July 30th in South Australia. The cross marks the radiant  (the point where the meteors appear to originate from) of the Southern Delta Aquariids.  Similar views will be seen elsewhere at the equivalent local time (click to embiggen).

The Southern Delta-Aquarids meteor shower runs from from 12 July to 23rd August, peaking on Wednesday July the 30th. The number of meteors you will see depends on how high the radiant is above the horizon, and how dark your sky is. This shower is fairly faint, with the highest rate of around a meteor every 4 minutes (more detail below).

The ZHR  for Southern Delta Aquariids is 16 meteors per hour. 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, moonlight will significantly reduce rates. How many are you likely to see in reality? I discuss this further down, lets talk about when to see them first.

At 10 pm, face east, and look 4 hand spans and two finger widths above the horizon. One finger width right is the 4th magnitude star delta Aquarii. The radiant is just above this star. This meteor shower should be visible from 10.00 pm until dawn. The best rates will be at 2 am in the morning of the 30th. The radiant will be due north then, and close to the Zenith near the bright star Fomalhaut.

At 2 am people in the suburbs should see a meteor around once every 8 minutes, and in the country about once every 4 minutes at 2 am in the morning of the 30th.

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. Be patient, although you should see an average of a meteor every six to three 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 sky will also be particularly beautiful, with the Milky Way stretching over the sky and constellation of Scorpius and Mars and Saturn gracing the western sky.

Use the NASA  meteor shower flux estimator for an estimate of what the shower will be like from your location. You need to choose 5 Southern Delta Aquariids and remember to set the date to 29-30 July or 30-31 July 2016.

Cloud cover predictions can be found at SkippySky.


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