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04/08/2019 – Ephemeris – How to find Polaris, the North Star

April 8, 2019 Comments off

Ephemeris for Monday, April 8th. Today the Sun will be up for 13 hours and 7 minutes, setting at 8:18, and it will rise tomorrow at 7:09. The Moon, 3 days past new, will set at 11:54 this evening.

The most useful of the navigation stars for the average person is Polaris, the North Star or Pole Star. It is very close to the point in the sky that the Earth’s axis points to in the north. Currently it is about three-quarters of a degree from the pole, about one and a half moon diameters. In 2110 or thereabouts it will approach to slightly less than a moon diameter from the pole before slowly heading away. Polaris is always closer to true north than a magnetic compass in Michigan. To find it use the two stars in front of the Big Dipper’s bowl to point to it. This time of year the Big Dipper is above Polaris, so the pointer stars, that’s what they are called, point down to it. Polaris is at the end of the handle of the faint Little Dipper.  The reason for Polaris’ motion is the slow 26,000 year wobbling of the Earth’s axis, called precession.

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

Addendum

Pointing to Polaris

Ursa Major and Minor, the Big and Little Dippers. See how the two stars at the front of the bowl point to Polaris. It happens that the pointer stars are close to the 11th hour of right ascension (longitude in the sky). The right ascension lines converge at the north celestial pole, just as the longitude lines converge at the Earth’s north pole. Created using Stellarium.

The year I was born, 1941, Polaris was a whole degree from the celestial north pole.

If you’ve ever wondered why right ascension is in hours instead of degrees it’s because the Earth rotates within the celestial sphere, so it’s easier to keep track of the east-west position in the sky by using a clock that set to gain 3 minutes and 56 seconds a day.  Such a clock keeps sidereal (star) time rather than solar (sun) time.  One hour equals 15 angular degrees or 4 minutes a degree.

 

03/26/2019 – Ephemeris – Mars is approaching the Pleiades this week

March 26, 2019 Comments off

Ephemeris for Tuesday, March 26th. Today the Sun will be up for 12 hours and 27 minutes, setting at 8:02, and it will rise tomorrow at 7:33. The Moon, 2 days before last quarter, will rise at 2:38 tomorrow morning.

Daylight time and spring time are catching up with us with the Sun setting now just after 8 p.m. By 9 p.m. tonight the brighter stars appear and most of the well known constellations will be recognizable. Looking off to the west at that time the famous star group of the Pleiades, or Seven Sisters will appear. Folks with good eyesight can see six or maybe even seven of its stars. Tonight, right below the Pleiades is a bright reddish star. It would be the 22nd of the first magnitude stars, except it’s not a star. It’s a wanderer, according to the ancient Greeks, one of seven*. They called it Ares the god of war. The Romans turned it into Mars. Over the week Mars will be closing in and passing by the Pleiades this weekend.

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

Addendum

Pleiades, Mars, zodiacal light

The western sky at 10:22 last night March 25, 2019. Mars appears below the Pleiades in zodiacal light. Credit, mine – Canon EOS Rebel T5 18mm f.l., f/3.5, 8 sec. ISO 12,800.

Mars passing the Pleiades

Mars tiptoeing past the Pleiades nightly from March 26th to April 1st, 2019 at 9 p.m. Looking west. Created using Stellarium and GIMP.

The letter V of stars to the left of the Pleiades is the Hyades, in mythology the half sisters to the Pleiades.  It is also the face of Taurus the bull.

* We get the word planet from the Greek planētes meaning wander.  Five are the classical planets, Mercury, Venus, Mars, Jupiter, and Saturn.  The other two are the Sun and Moon.  The other celestial objects were the fixed stars.  Other things that appear in the sky, like comets, novae and meteors were thought to be in the Earth’s atmosphere.

03/25/2019 – Ephemeris – Zodiacal light is visible in the west again

March 25, 2019 Comments off

Ephemeris for Monday, March 25th. Today the Sun will be up for 12 hours and 24 minutes, setting at 8:01, and it will rise tomorrow at 7:35. The Moon, 3 days before last quarter, will rise at 1:37 tomorrow morning.

With the bright moon out of the sky for nearly two weeks it’s time to look for the zodiacal light. It’s is a faint but towering glow that can be seen after the end of astronomical twilight on moonless nights. It is seen in the west in the evening in late winter and early spring and in the east in the morning in late summer and early autumn. The axis of the glow is the ecliptic, the apparent annual path of the Sun in the sky, along which lie the constellations of the zodiac. Right now the end of astronomical twilight is about 9:45 p.m. and advancing at a rate of a minute or two each night. Go to a spot with a dark western sky, no big cities or towns out that way. Zodiacal light is caused by dust spread out around the Sun.

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

Addendum

Zodiacal Light

Much enhanced Zodiacal Light from the my back yard at 9:31 p.m. March 16, 2018, 5 minutes after the official end of astronomical twilight. Note the Pleiades top left of center and the constellation of Ares below and right of center. Canon EOS Rebel T5 18mm f.l., f/3.5, 6 sec. ISO 12,800 . The clouds on the left appear to be illuminated by the lights of the towns of Beulah and Frankfort 20+ miles away.

Added ecliptic line

I’ve added the approximate ecliptic line from a Stellarium view of the same date and time.

03/04/2019 – Ephemeris – Zodiacal light is especially visible this time of year

March 4, 2019 Comments off

Ephemeris for Monday, March 4th. Today the Sun will be up for 11 hours and 18 minutes, setting at 6:34, and it will rise tomorrow at 7:13. The Moon, 2 days before new, will rise at 7:07 tomorrow morning.

Zodiacal light is a faint but towering glow that can be seen after the end of astronomical twilight on moonless nights. It is seen in the west in the evening in late winter and early spring and in the east in the morning in late summer and early autumn. The axis of the glow is the ecliptic, the apparent annual path of the Sun in the sky, along which lie the constellations of the zodiac. Right now the end of twilight is about 8 p.m. and advancing at a rate of a minute or two each night. The cause of zodiacal light is dust, micron sized dust from comets and asteroids. Most of these lie in the plane of the solar system, centered on the ecliptic and the constellations of the zodiac and increases in brightness and width toward the Sun.

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

Addendum

Zodiacal Light

Much enhanced Zodiacal Light from the my back yard at 9:31 p.m. March 16, 2018, 5 minutes after the official end of astronomical twilight. Canon EOS Rebel T5 18mm f.l., f/3.5, 6 sec. ISO 12,800 . The clouds on the left appear to be illuminated by the lights of the towns of Beulah and Frankfort 20+ miles away.

Zodiacal Light and Comet Hale-Bopp April 1997. Enhanced contrast.

This is my previous best photo of zodiacal light. Zodiacal Light and Comet Hale-Bopp April 1997. Enhanced contrast.

The latest versions of Stellarium also show zodiacal light, but to see it the atmosphere needs to be turned off.  That’s keyboard shortcut A.

02/18/2019 – Ephemeris – Super Moon, super math

February 18, 2019 Comments off

Ephemeris for President’s Day, Monday, February 18th. Today the Sun will be up for 10 hours and 36 minutes, setting at 6:15, and it will rise tomorrow at 7:37. The Moon, 1 day before full, will set at 7:52 tomorrow morning.

Ready for some math this morning? This will be easy, because you will only have to think about it. Let’s say the Earth’s radius is 4,000 miles.  That is pretty close to its actual value. OK, it is 3961 miles (6,378 km) at the equator. The Earth is nearly spherical. At 4 this morning the Moon passed perigee, its closest point to the Earth, making tomorrow’s full moon a super-moon. Let’s say it will be at today’s distance of 221,600 miles (356,800 km). That’s center to center. At moon rise or moon set the Moon is near that center to center distance, but if it moves overhead it’s 4,000 miles closer because we are on the Earth facing the Moon. Even though the Moon looks smaller than when it appears on the horizon. It’s an optical illusion that the Moon appears larger when it is rising. Super moon or not.

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

Addendum

The difference in the Moon's distance at rising (or setting) versus when it is overhead

This illustrates the difference in the Moon’s distance at rising (or setting) versus when it is overhead. BTW today’s perigee puts the Moon at only 56 Earth radii from the Earth. The illustration is mine.

02/07/2019 – Ephemeris – Siriusly, folks.

February 7, 2019 Comments off

Ephemeris for Friday, February 8th. Today the Sun will be up for 10 hours and 7 minutes, setting at 6:01, and it will rise tomorrow at 7:52. The Moon, half way from new to first quarter, will set at 9:48 this evening.

At 9 in the evening the great constellation of Orion the hunter can be seen in the south. Its large rectangle of bright stars is now upright, while in the center is a row of three stars, his belt. These stars tilt downward to the left to a very bright star merrily twinkling in the south-southeast. This star is called Sirius, also known as the Dog Star because it’s in the heart of Orion’s larger hunting dog, Canis Major. It is an arc light white star as seen in binoculars or telescope. It’s a neighboring star, just twice the distance of the closest star to the sun at 8.6 light years. It’s name, Sirius, has nothing to do with a dog, but is from the Greek meaning scorching for its brightness or sparkling, due to its intense twinkling.

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

Addendum

Orion's Belt points to Sirius

Orion’s Belt points to Sirius. Created using Stellarium.

12/19/2018 -Ephemeris – The Bright planets and a departing comet for this week

December 19, 2018 Comments off

Ephemeris for Wednesday, December 19th. The Sun will rise at 8:15. It’ll be up for 8 hours and 48 minutes, setting at 5:04. The Moon, 3 days before full, will set at 5:34 tomorrow morning.

Let’s look at the bright planets for tonight. In the evening sky we have Mars still visible, but Saturn is lost in the bright twilight. It will pass conjunction with the Sun on New Years day. Mars will be due south at 6:19 p.m., and it will set at 12:08 a.m. Mars is moving eastward, crossing the constellation of Aquarius until the 21st, when it enters Pisces. Comet Wirtanen is moving northward, to the left of the Pleiades and fading as the moonlight gets brighter. On the 23rd at 9 p.m. it will be a degree and a half, that’s 3 moon widths below and a bit left of the star Capella. Venus, our brilliant morning star, will rise at 4:20 a.m. in the east-southeast. The planets Jupiter and Mercury will be low on the southeastern horizon by 7 a.m. tomorrow..

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

Addenda

Bright planets and the Moon

Evening planets

Mars, and the Moon at 8 p.m. tonight December 19, 2018. Click on image to enlarge. Created using Stellarium.

Binocular Moon

The waxing gibbous Moon as it should appear tonight in binoculars. Created using Stellarium.

Morning planets

Morning planets Venus, Mercury and Jupiter on December 20, 2018, 7 a.m.. Created using Stellarium.

Telescopic Venus

Telescopic view of Venus tomorrow morning December 20, 2018. Created using Stellarium.

Planets and the Moon on a single night

Planets, two comets and the Moon at sunset and sunrise of a single night starting with sunset on the right on December 19, 2018. The night ends on the left with sunrise on the 20th. Click on the image to enlarge. Created using my LookingUp program.

Comets

Comet C/2018 V1

Comet C/2018 V1 (Machholz-Fijikawa-Iwamoto) in twilight starting tonight December 19, 2018. This comet is basically invisible in the evening twilight of 6 p.m. on the rest of the nights because the stars in the field will set 4 minutes earlier each successive evening. The latest magnitude observed is two magnitudes brighter than shown here. Created using Cartes du Ciel (Sky Charts).

Comet 46P/Wirtanen

Comet 46P/Wirtanen positions for the next week in a bright moonlit sky. Positions are marked with month-date and magnitude. The observations are about 5.5 magnitudes brighter than shown here. Star field position is for 9 p.m. on the 19th. Click on the image to enlarge. Created using Cartes du Ciel (Sky Charts).