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Archive for August, 2014

08/29/2014 – Ephemeris – Twilight is shorter now than it was in June

August 28, 2014 2 comments

Ephemeris for Friday, August 29th.  The sun will rise at 7:01.  It’ll be up for 13 hours and 22 minutes, setting at 8:24.   The moon, half way from new to first quarter, will set at 10:09 this evening.

Here we are at the end of August already.  We have one more night to view the Milky Way in darkness after the moon sets, because the Moon sets at the very end of astronomical twilight.  By the way, astronomical twilight starts and ends when the sun is 18 degrees below the horizon, and the actual twilight glow is completely gone.  The sun sets more than an hour before it did in late June, which means that it gets dark much earlier.  Twilight lasted much longer in June than it does now because the Earth’s rotation now drops the sun below the horizon at a steeper angle.   As a matter of fact while the sun sets an hour earlier now than in June, twilight ends two hours earlier.  It sneaks up on you if you’re not paying attention to it.

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

Addendum

Tonight's end of astronomical twilight

Distance the Sun must travel from the horizon to 18 degrees below tonight, August 29, 2014. Created using Stellarium.

 Solstice end of twilight

Distance the Sun must travel from the horizon to 18 degrees below, the night after the June solstice, June 22, 2014. Created using Stellarium.

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08/28/2014 – Ephemeris – The evening Moon will stay low in the sky for the next couple of weeks.

August 28, 2014 Comments off

Ephemeris for Thursday, August 28th.  The sun will rise at 7:00.  It’ll be up for 13 hours and 25 minutes, setting at 8:26.   The moon, 3 days past new, will set at 9:40 this evening.

Since we’re within a month of the autumnal equinox, coming up on September 22nd, something funny is happening with the Moon rise and set times near both new and full moon.  That is they aren’t changing very much.  Here we are with the Moon three days old, and it still sets before the end of astronomical twilight.  You may notice that for the next two weeks, that the Moon doesn’t get very high in the sky in the early evening.  It’s path stays close to the horizon.  Around first quarter next Tuesday the Moon will get to be just a little higher in the sky than the sun does on the first day of winter.  The next full moon is the Harvest Moon, being the full moon closest to the first day of autumn.  Then the day-to-day succession of rise times again will slow.

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

Addendum

Low Moon

The Moon on September 3, 2014 a day after first quarter. It will rise higher after that if one stays up long enough. Created using Stellarium.  Click on image to enlarge.

In the image above the Moon’s orbit is compared to the ecliptic, the plane of the Earth’s orbit to which it’s inclined by about 5º.  Note the two points where these lines cross.  The point where the Moon’s orbit crosses the ecliptic heading northward is called the ascending node.  The crossing point heading southward is the descending node.  The important thing about that is the when the moon passes a node while at new or full, an eclipse will occur,  which they will do in October.  There will be a total lunar eclipse on the morning of October 8th, then a partial solar eclipse on October 23rd as the sun is setting here in northern Michigan.  I’ll have more information as the events gets closer.

08/27/2014 – Ephemeris – Where are the bright planets for this week?

August 27, 2014 Comments off

Ephemeris for Wednesday, August 27th.  The sun will rise at 6:59.  It’ll be up for 13 hours and 28 minutes, setting at 8:27.   The moon, 2 days past new, will set at 9:12 this evening.

Let’s take our weekly look at the bright planets.  Reddish Mars is in the constellation of Libra the scales, skirting below, left of Saturn in the southwest as darkness falls.  It is in conjunction with Saturn today, as it passes due south of the ringed planet.  Mars will set at 11:07 p.m.  Saturn will set at 11:23 p.m.  Saturn viewing with a telescope will suffer because it’s getting close to the horizon but it’s still possible to see those fabulous rings and its large moon Titan.  Brilliant Jupiter will rise in the east-northeast at 4:44 a.m. tomorrow, followed by the brighter Venus, which will rise at 5:37 a.m.  Jupiter is increasing its distance from the sun, while Venus is retreating toward the Sun from our point of view.

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

Addendum

Evening planets

Saturn and Mars in conjunction at 9:30 p.m., August 27, 2014. Created using Stellarium.

Saturn

Telescopic Saturn. Do not expect to spot any other of Saturn’s moon other than Titan. 9:30 p.m., August 27, 2014.  Created using Stellarium.

Morning planets

Jupiter and Venus and the rising winter constellations at 6 a.m. August 28, 2014. Created using Stellarium.

Telescopic Jupiter

Telescopic view of Jupiter and its 4 Galilean moons at 6 a.m. on August 28, 2014. Created using Stellarium.

08/26/2014 – Ephemeris – The Great Rift

August 26, 2014 Comments off

Ephemeris for Tuesday, August 26th.  The sun rises at 6:57.  It’ll be up for 13 hours and 31 minutes, setting at 8:29.   The moon, 1 day past new, will set at 8:45 this evening.

High overhead the Milky Way is seen passing through the Summer Triangle of three bright stars.  Here we find the Milky Way split into two sections.  The split starts in the constellation of Cygnus the Swan or Northern Cross very high in the east.  The western part of the Milky Way ends southwest of the Aquila the eagle.  This dark dividing feature is called the Great Rift.  Despite the lack of stars seen there, it doesn’t mean that there are fewer stars there than in the brighter patches of the Milky Way.  The rift is a great dark cloud that obscures the light of the stars behind it.  Sometimes binoculars can be used to find the edges of the clouds of the rift, as stars numbers drop off suddenly.  This is especially easy to see in Aquila.

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

Addendum

The Great Rift in the Milky Way. Created using Stellarium.

The Great Rift in the Milky Way. Created using Stellarium.

08/25/2014 – Ephemeris – Cool treasures in the constellation of Lyra

August 25, 2014 Comments off

Ephemeris for Monday, August 25th.  The sun rises at 6:56.  It’ll be up for 13 hours and 34 minutes, setting at 8:31.  The moon is new today, and won’t be visible.

The bright star Vega will be nearly overhead tonight at 10 p.m.   It will be about 6 degrees south of the zenith.  That’s quite a stretch of the neck to spot, with its accompanying stars in a small parallelogram that make up the constellation of Lyra the harp.  Lyra has some interesting features for a serious observer with and without a telescope.  The bottom right star of the parallelogram, if south is toward the bottom, is a star called Beta Lyrae that changes brightness by a factor of 3 in a period of 13 days.  Another star near Vega looks like two close stars in binoculars, in telescopes each is again a double stars.  That’s Epsilon Lyrae.  The jewel of this constellation needs a telescope to find between the two bottom stars of the parallelogram, the famous Ring Nebula.

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

Addendum

A bi more stars than what will be seen in binoculars of the constellation Lyra.  Created using Cartes du Ciel (Sky Charts).

A bi more stars than what will be seen in binoculars of the constellation Lyra. Created using Cartes du Ciel (Sky Charts).

In the chart above:

The star designated α is Vega
The star designated β is Beta Lyrae
The stars designated ε1 and ε1 is Epsilon Lyrae
The object designated M57 is the Ring Nebula

Ring Nebula 1

The Ring Nebula. Visually one cannot detect the color. It takes a large telescope to see the central star. Credit: Stellarium.

The Ring Nebula, AKA M57 by amateur astronomers, is a planetary nebula.  The name planetary is a misnomer.  Many of these objects look like the dim planets Uranus and Neptune.  They are really stars like the sun, in their death throes puffing out their outer layers of gas at the end of their red giant stage.  See below the latest image of the Ring Nebula I recently found on the Phil Plait’s Bad Astronomy Blog.  It includes an explanation of what’s in the image.

Deep Ring Nebula

Photo by NASA, ESA, and C. R. O’Dell (Vanderbilt University) and Robert Gendler

Click on the image to get lost in the Ring Nebula!

 

08/22/2014 – Ephemeris – Cassiopeia Rising

August 22, 2014 Comments off

Ephemeris for Friday, August 22nd.  The sun rises at 6:53.  It’ll be up for 13 hours and 43 minutes, setting at 8:36.   The moon, 3 days before new, will rise at 5:08 tomorrow morning.

Now in the northeastern sky at 10 p.m. or later is the constellation of Cassiopeia the queen, which looks like, in its current orientation like the letter W.  The Milky Way runs through it, if you trace the Milky Way from the zenith back to the northeast.  The milky band isn’t as bright here as it is in the teapot shaped Sagittarius to the south.  That’s because in looking to the south we are looking toward the star clouds of the dense spiral arm toward the center of the galaxy.  In Cassiopeia, and in the winter sky, we are looking out to the less populated galactic arms farther out from the center of the Milky Way.   Cassiopeia can be found using the Big Dipper.  A line from the star Mizar at the bend of the handle of the dipper through Polaris points to Cassiopeia.  Cassiopeia doesn’t set for us in northern Michigan.

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

Addendum

Finding Cassiopeia

Finding Cassiopeia using the Big Dipper or Ursa Major at 10 p.m. August 22, 2014 using the angle measurement tool as a pointer. Created using Stellarium.

08/21/2014 – Ephemeris – What do a dolphin, an arrow and a coffin have in common?

August 21, 2014 Comments off

Ephemeris for Thursday, August 21st.  The sun rises at 6:52.  It’ll be up for 13 hours and 46 minutes, setting at 8:38.   The moon, half way from last quarter to new, will rise at 4:12 tomorrow morning.

Located below the eastern edge of the Summer Triangle of three of the brightest stars in the sky, which is high in the southeast in the sky at 10 p.m., is the tiny constellation of Delphinus the dolphin.  Delphinus’ 6 stars in a small parallelogram with a tail, really does look like a dolphin leaping out of the water.  The parallelogram itself has the name Job’s Coffin.  The origin of this asterism or informal constellation is unknown.  Of the dolphin itself: the ancient Greeks appreciated this aquatic mammal as we do, and told stories of dolphins rescuing shipwrecked sailors.  There’s another tiny and slender constellation to the right of Delphinus called Sagitta the arrow, which is said to represent Cupid’s dart.

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

Addendum

Delphinus, Sagitta and the Coat hanger. Diagram created using Stellarium.

Delphinus, Sagitta and the Coat hanger. Diagram created using Stellarium.

The Coat hanger is strictly a binocular asterism.  However it was discovered by the great Arabian astronomer Al Sufi inn the 10th century, and is currently designated Collinder 399.  It is actually a random pattern of unrelated stars.

Constellation figures

Delphinus and Sagitta images along with the stars and constellations of the Summer Triangle. Created using Stellarium.