This year's eta Aquarid meteor shower is already underway and is predicted to peak at 0100 UT on the 6th of May. In fact
radio meteor observers have been reporting unusually strong activity in the last couple of
days. It might be that the shower has peaked early this year, or it might be that this years predicted peak will be stronger than usual (less likely I
suspect), or it could simply be a strong sub-peak that has not been predicted.
The eta Aquarid meteor shower is caused when Earth encounters the debris ejected from Halley's Comet, which occurs twice every year, also giving rise
to the Orionid meteor shower in October.
Whilst the eta Aquarids are best observed from the Southern hemisphere, they can also be observed from the Northern hemisphere where rates are about
half those in the Southern hemisphere. Observers in the Southern hemisphere can expect to see as many as 20-30 eta Aquarid meteors per hour in an
average year if observing under ideal conditions at the peak of the shower.
The shower is named after a 4th-magnitude star in the constellation Aquarius. The star has nothing to do with the meteor shower except that,
coincidentally, meteors appear to emerge from a point nearby. Eta Aquarii is 156 light years from Earth and 44 times more luminous than the Sun.
The constellation Aquarius does not rise very far above the horizon in the northern hemisphere, and that's why northerners see relatively few
meteors. But the ones they do see could be spectacular Earthgrazers.
Earthgrazers are meteors that skim horizontally through the upper atmosphere. They are slow and dramatic, streaking far across the sky. The best time
to look for Earthgrazers is between 2:00 to 2:30 a.m. local time when Aquarius is just peeking above the horizon.
Experienced meteor watchers suggest the following viewing strategy: Dress warmly. Bring a reclining chair, or spread a thick blanket over a flat spot
of ground. Lie down and look up somewhat toward the east. Meteors can appear in any part of the sky, although their trails will point back toward
Eta Aquarid meteoroids hit Earth's atmosphere traveling 66 km/s.
Typical eta Aquarid meteors are as bright as a 3rd magnitude star.
This great video covers almost everything, but I would argue on a few points that were mentioned:
1. It's usually better to be totally flat when observing meteors since you can catch meteors close to any horizon with your peripheral vision when
facing directly upwards.
2. If you live in a warm/tropical climate, you might get away with a blanket (or even less) to keep you warm, but I'd advise putting on multiple
layers of warm cloths, and jumping into a sleeping bag if you want to observe for any length of time if you live away from the equator. If you are too
warm (unlikely in most cases) then you can always remove a layer of cloths or two.
3. The camera exposure times he mentioned could be at the upper end of the scale if you have any light pollution at you're site and/or depending on
your equipment/settings/how you want your photo to appear. It's worth experimenting before hand, but if you are using fast lenses/high ISOs (which
you should be if you want to catch any meteors, although you may get lucky and catch a bright meteor anyway), exposures can be as short as 5 or 10
seconds. See links below for more info.
For most observers, the Eta Aquariids are only visible during the last couple
hours before the start of morning twilight. The reason for this is that the radiant is situated approximately sixty degrees west of the sun. Therefore it
rises before the sun in the morning hours. The time of radiant rise is between
2:00 and 3:00 local daylight time (LDT), depending on your longitude. The real
key is the latitude. There is an observing window for this shower between the
time the radiant rises and the beginning of morning nautical twilight. This
window ranges from zero at 60 degrees north latitude to all night in Antarctica.
Unfortunately in Antarctica, the radiant never rises very high in the sky. The
best combination of a large observing window and a decent radiant altitude
occurs between the equator and 30 degrees south latitude. From this area the
radiant reaches a maximum altitude of 50 degrees at nautical twilight. The
observing window ranges from 3.5 hours at the equator to slightly over 4.0 at 30
degrees south latitude. Going further south will increase your observing window
but the maximum altitude will begin to fall closer to the horizon.
Since most meteor observers live in the northern hemisphere, here are the
conditions at several different latitudes: the observing window for 50N is 1.5
hours with a radiant altitude of 15 degrees. The observing window for 40N is
2.25 hours with a radiant altitude of 25 degrees. The observing window for 30N
is 2.75 hours with a radiant altitude of 35 degrees.
There are many reports that the eta Aquarids are currently undergoing an outburst. It may be starting to subside however, but if you are in the
Southern hemisphere, and it's dark, or in the Northern hemisphere and it's 1-3 hrs before dawn, you may see some.
I was also monitoring early this morning, and took a couple of screen shots. It helps if you monitor in "2D" (there's a link at the top of the
monitoring page) as well - you can easily tell which are meteors and which is interference.
Here's the example of a meteor I caught in both 2D and 3D. I've marked the meteor with a green arrow in the 2D screen shot, and the direction where
the depth that I mentioned earlier indicates a meteor in the 3D view.
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