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Archive for the ‘Asterism’ Category

11/13/2018 – Ephemeris – The Summer Triangle in autumn

November 13, 2018 Comments off

Ephemeris for Tuesday, November 13th. The Sun will rise at 7:37. It’ll be up for 9 hours and 39 minutes, setting at 5:16. The Moon, 2 days before first quarter, will set at 10:20 this evening.

The Summer Triangle is still in the sky at 9 p.m., even though it’s November. These three bright stars that straddle the Milky Way are high in the east for most of the summer, move overhead and begin to slide to the west in autumn. We will lose Altair, the southernmost of the three stars at 9 p.m. on the winter solstice, December 21st. We’ll lose the brightest, Vega in January. For the northern half of the IPR listening area the northernmost of the triangle stars, Deneb won’t quite set below a north Lake Michigan horizon. Next spring we’ll be waiting and watching for these three stars to rise, reclaim the skies, and bring again the warm summer skies. The winter skies do however have more bright stars than the summer sky.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Summer Triangle tonight
The Summer Triangle of the three bright stars Vega, Deneb and Altair is still high in the west at 8 p.m. tonight. The zenith is near the top of the image. Created using Stellarium
Summer Triangle about to set.
The Summer Triangle with Altair about to set on the winter solstice at 9 p.,. Created using Stellarium.
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09/10/2018 -Ephemeris – The Coathanger in the sky

September 10, 2018 Comments off

Ephemeris for Monday, September 10th. The Sun will rise at 7:15. It’ll be up for 12 hours and 47 minutes, setting at 8:02. The Moon, 1 day past new, will set at 8:57 this evening.

Just about every amateur astronomer knows a little asterism or informal constellation called the Coathanger. It’s stars are mostly below naked eye visibility, but it is a great sight in binoculars. It’s located along a line from Altair in Aquila the eagle to Vega in Lyra the harp. These are two star of the Summer Triangle. It is also just west of, or right of, the constellation Sagitta the arrow. It consists of six stars in just about a perfectly straight line with four stars in a tight group south of them making the hook. In telescope finders which invert the image the Coathanger appears right-side-up. Arab astronomer Al Sufi discovered it and described it in 964 AD. It has the catalog designation of Collinder 399. It is also known as Brocchi’s Cluster.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Coathanger finder animation

How to find the Coathanger. Look for the Summer Triangle. On the line from Altair to Vega the Coathanger can be found. Star imaged by Bob Moler.

Binocular view of the Coathanger

Binocular view of the Coathanger. From the original resolution of the above photograph.

Telescope finder view of the Coathanger

Telescope finder view of the Coathanger. Telescope finders usually invert the image, so it looks like a proper coat hanger.

07/02/2018 – Ephemeris – The starry triangle of summer

July 2, 2018 Comments off

Ephemeris for Monday, July 2nd. Today the Sun will be up for 15 hours and 30 minutes, setting at 9:31, and it will rise tomorrow at 6:02. The Moon, half way from full to last quarter, will rise at 12:19 tomorrow morning.

Now that it’s summer it’s time to look for the Summer Triangle in the sky. It’s seen rising in the east as it gets dark. Highest of the three bright stars is Vega in the constellation Lyra the harp, whose body is seen in a narrow parallelogram nearby. The second star of the triangle is Deneb lower and left of Vega, It appears dimmer than Vega because it is by far the most distant of the three. The third star of the Summer Triangle is seen farther below and a right of Vega. It is Altair in Aquila the eagle, and the closest. Altair is 16.5 light years away, Vega is 27 light years while Deneb actually one of the brighter stars known, is 1500 or more light years away. It’s distance is not well known.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

The Summer Triangle July 5, 2012 at 11 p.m. Created using Stellaruim and The Gimp.

The Summer Triangle. Created using Stellarium.

04/23/2018 – Ephemeris – The Ursa Major Association

April 23, 2018 Comments off

Ephemeris for Monday, April 23rd. The Sun rises at 6:45. It’ll be up for 13 hours and 52 minutes, setting at 8:37. The Moon, 1 day past first quarter, will set at 4:15 tomorrow morning.

The usual impression is to think that the stars of a constellation are actually located close together. This is usually not true. The stars of a constellation can be at vastly different distances. The Big Dipper is different. The five stars, excepting the two end stars of the dipper and 12 other dimmer stars in the general area are of similar distance and have the same motion through space. The group is called the Ursa Major Moving Cluster or Ursa Major Association, and is moving about 9 miles per second relative to the solar system to the east and south. An association is a rather loose, sparse star cluster. This association lies about 75 light years away. If it were five times farther away, it would be the same distance as the Pleiades.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

The Big Dipper

Craig Brown’s drawing of where the stars of the Big Dipper are and are heading. Click on the image to go to Craig’s WordPress post.

04/19/2018 – Ephemeris – The Big Dipper’s stars Mizar and Alcor

April 19, 2018 Comments off

Ephemeris for Thursday, April 19th. The Sun rises at 6:51. It’ll be up for 13 hours and 41 minutes, setting at 8:32. The Moon, 3 days before first quarter, will set at 12:47 tomorrow morning.

The most interesting star in the Big Dipper is Mizar and its dim companion Alcor. It is the second star from the end of the handle, where the bend in the handle takes place. Folks with good vision can see the dimmer star right next to Mizar. In ancient times it was used as an eye test for visual acuity for warriors as such it was known as the “Horse and the Rider”.

Mizar is second magnitude, in the second rank of star brightness invented by the Greek astronomer Hipparchus in the 2nd century BC. He ranked stars in 6 classes, from first magnitude for the brightest to 6th for the dimmest visible to the naked eye. Alcor comes in at 4th magnitude. It does suffer a bit by being close to Mizar which is 6 times brighter.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

The Big Dipper with Mizar & Alcor

The Big Dipper, almost overhead at 10 p.m. April 19 with Mizar and Alcor pointed out. Created using Stellarium.

Telescopic Mizar and Alcor

A view of Mizar and Alcor as seen in a telescope. Mizar is itself a binary star. In actuality both components of Mizar and Alcor are spectroscopic binaries, which are too close to split, but their presence is detected by their Doppler motions with spectrographs. Created using Stellarium.

06/22/2017 – Ephemeris – Now that it’s summer, lets check out the Summer Triangle

June 22, 2017 1 comment

Ephemeris for Thursday, June 22nd. Today the Sun will be up for 15 hours and 33 minutes, setting at 9:31, and it will rise tomorrow at 5:57. The Moon, 1 day before new, will rise at 5:45 tomorrow morning.

We’re a day into summer, and the asterism or informal constellation called the Summer Triangle can be seen rising in the east as it gets dark. Highest of the three bright stars is Vega in the constellation Lyra the harp, whose body is seen in a narrow parallelogram nearby. The second star of the triangle is Deneb lower and left of Vega, It appears dimmer than Vega because it is by far the most distant of the three. The third star of the Summer Triangle is seen farther below and a right of Vega. It is Altair in Aquila the eagle, and the closest. Altair is 16.5 light years away, Vega is 27 light years while Deneb may be a whopping 2600 light years away. One light year is 6 trillion miles (9 trillion km).

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

The Summer Triangle July 5, 2012 at 11 p.m. Created using Stellaruim and The Gimp.

The Summer Triangle. Created using Stellarium and The Gimp.

05/23/2017 – Ephemeris – The Big Dipper as seen in many lands

May 23, 2017 Comments off

Ephemeris for Tuesday, May 23rd.  Today the Sun will be up for 15 hours and 6 minutes, setting at 9:12, and it will rise tomorrow at 6:05.  The Moon, 2 days before new, will rise at 5:38 tomorrow morning.

The Big Dipper is overhead at 10 in the evening, it’s seven stars shining brightly. The Big Dipper is not an actual constellation, recognized internationally. It’s part, the hind part, of Ursa Major, the great bear. The Big Dipper is an asterism or informal constellation. It is a distinctly North American constellation. For fugitive slaves, fleeing the southern states in the days before the Civil War, the Drinking Gourd, as they called it, showed the direction north to freedom. In England the dipper stars become the Plough, or Charles’ Wain (Charlemagne’s Wagon), In France, known for culinary delights it was the saucepan, or the cleaver. So many cultures saw what was familiar to them in these seven bright stars.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

The many faces of the Big Dipper

The Big Dipper as I imagine it from some lands facing southwest and looking straight up. The X in the picture is the zenith point. We cycle through the stars only, the Big Dipper or the Saucepan, The Plough (plow in the U.S.), Charles Wain, and finally the Cleaver. Created using my LookingUp program.

Do you know any other asterisms or informal constellations assigned to these stars, add a comment.