by John Hlynialuk, Bluewater Astronomical Society

Summer came to an official end this year on Sep 22 at 9:54 pm EDT, -more or less its usual time. The autumnal equinox date varies from year to year but always occurs when the Sun appears to pass exactly over the Earth's equator. If you happen to be near or on the equator at that time, instead of looking up, look down. Your shadow will fall directly beneath you, something that you will never see in the northern hemisphere. The fall equinox comes at a time between Sep 21 and Sep 24 and there is one main reason for the variation. The length of one Earth rotation does not divide evenly into the length of the year, there is that pesky quarter of a day left over. The explanation becomes complicated quickly and is not the main topic of this column, so enough said on that.

In 2019, the fall equinox will be on Sep 23, at 3:50 am EDT, one of the latest dates for an equinox. Most of the recent ones have been later rather than earlier and you have to go back 87 years (1931) for a fall equinox that happened Sep 21. There will be another one of these in 2092. If you are holding out for the Sep 24 date, you need to refrain from dying until 2303. I suggest you eat your veggies and pray for a major discovery in longevity or cryogenics.

So, in October, we are officially into fall but the night sky is still in summer mode. The two summer astronomical objects on prominent display are the summer Milky Way and the Summer Triangle, and it will be well into winter before both disappear below the western horizon. So let's say a proper goodbye to the summertime night sky.

For the next few months, when clouds part long enough at night for you to see anything, the Milky Way stands vertically over the SW horizon and stretches overhead and behind you. At a dark sky location, you can follow the glow of our home galaxy right to the northeastern horizon. Star charts are available on the BAS website www.bluewaterastronomy.com under the CHARTS/FORMS tab and also at www.skymaps.com and an all-sky chart is included here. Start by looking southwards and locate the most obvious patch of Milky Way just above the southwestern horizon. The constellation there is Sagittarius, looking like a teapot tipped somewhat to the right. Say a hello in passing to Saturn just off the lid of the teapot. Now follow the Milky Way glow up to Aquila and overhead to Cygnus. Then turn around, face north and continue down past Cassiopeia to Perseus low above the northeastern horizon. At a dark site you should be able to trace the glow of the millions of stars that make up the Milky Way from horizon to horizon. The glow is more obvious in Sagittarius because you are looking toward the centre of the galaxy where more stars are concentrated. In the opposite direction, looking past Perseus, you are gazing out into the less starry regions beyond the edge of our home in the Universe.

To locate the Summer Triangle, find the bright "alpha" stars of Cygnus, Lyra and Aquila. This is not hard as these constellations are straight up at the zenith right now. Look for

the three brightest stars that together form a large right-angled triangle. Those stars are Deneb, Vega and Altair, -hints are on the chart.

It will be several months before this asterism disappears completely and even at years-end, Deneb will still be visible before midnight above the NW horizon. In December, of course, no one will be thinking about summer and the only "Milky Way" will probably be steam rising from mugs of hot chocolate as hardy stargazers check out our winter constellations.

As for other sky objects, there are only two bright planets left in the night sky, Mars and Saturn. Venus is lost in solar glare low in the west and Jupiter is close behind. Both drop quickly into the western sunset glow and by 9 pm, the time of the included chart, both have disappeared. The remaining planets, Saturn and Mars, are not labelled on the chart but they are not hard to find, -both are bright enough to be the first "stars" you see at night.

Let's hope for a few nice, not too frosty, autumn nights to catch the last of the offerings of the summer sky. And if it is too cloudy, do some armchair astronomy by reading my weblog on the BAS website.

Clear skies!