# Astronomers use coordinate systems to plot the position of stars in the night sky

Astronomy questions and answers – Looking up into the night sky you probably wonder how ancient stargazers were able to navigate using the stars in the night sky as their guide. One of the first things ancient stargazers did to help them navigate the night sky and the surface of the Earth was to create a coordinate system to pinpoint relative positions of the stars in the night sky in relation to one another.

Looking upward into the night sky, imagine the sky above you as a sphere of infinite size, centered on the Earth. This technique works in general because distances to the stars above you is not discernible using your naked eye, so the objects you see above you in the night sky all appear to lie on a great sphere at an infinite distance in relation to you.

Modern astronomers use two coordinate systems to determine the relative positions of objects in the night sky; the altitude-azimuth coordinate system and the equatorial coordinate system. We will talk a little about both coordinate systems currently being used by modern astronomers to help them plot the positions of the objects they view in the night sky and using celestial objects you view on your “Journey to the Beginning of Space and Time” to navigate your way through the universe.

In the altitude-azimuth coordinate system, altitude indicates the number of degrees from the horizon to the object in the night sky you’re viewing and ranges from 0 degrees at the horizon to 90 degrees at the zenith above you. Modern astronomers measure azimuth along the horizon from north to east, to the point where a line passing through the object in the night sky intersects the horizon at a right angle, and azimuth varies between 0 degrees and 360 degrees. Astronomers also subdivide each degree of azimuth into 60 arcminutes and each arcminute into 60 arcseconds, which helps to further subdivide the immense distances between each degree of measurement in the night sky.

The altitude-azimuth coordinate system doesn’t take into account the rotation of the Earth, though, and astronomers have solved this problem by fixing coordinates to the celestial sphere you imagine above you in the night sky. Celestial cartographers have created “celestial globes”, similar to the globes of the Earth that cartographers have devised for centuries to show the Earth and all of its features. On these celestial globes, you’ll find terms like the celestial equator and North and South celestial poles.

In the equatorial coordinate system, astronomers use two aspects called declination and right ascension to fix a star’s position on the celestial sphere you picture above you. Declination is analogous to Earth’s latitude and represents the angle between the object you’re viewing in the night sky above you and the celestial equator. Declination varies between 0-90 degrees, North and South of the celestial equator, and is measured in degrees, arcminutes, and arcseconds while a minus sign is used to designate objects south of the celestial equator.

The lines of circles that run through the celestial poles perpendicular to the celestial equator represent the hour circle of objects in the night sky above your head and are analogous to the meridian of longitude on the Earth. In order to fix an object’s position in the celestial sphere above you, we’ll also need to set the zero point of the longitude coordinate of the object, which astronomers call the object’s right ascension. In order to accomplish this, we need an intersection point between the Earth’s equator and its orbital plane, the ecliptic. Astronomers call this intersection point the vernal equinox and the sun appear to travel through the intersection point annually around March 21, as it moves South to North crossing the celestial equator.

The angle that lies between the vernal equinox and the point where the hour circle of the celestial object in question intersects the celestial equator is the right ascension of the object you see in the night sky. Right ascension is measured in hours (h), minutes (m), and seconds (s), from west to east, and the vernal equinox is zero-hour. There are about 24 hours in each day on the Earth, so each hour of right ascension in the night sky corresponds to 15 degrees of longitude.

The movement of the Earth and the objects in the night sky above you mean the appearance of the night sky is dynamic in nature, so celestial objects will appear to circle the celestial poles as you watch the night sky. A star with a greater distance from a celestial pole than your latitude will only be visible to you during a portion of its orbit. In this case, the star will rise in the east and set in the west. Stars that are always above your horizon are circumpolar for your latitude and you’ll see these stars for their entire orbit.

The Earth’s rotation and the movement of the stars also mean the constellations in the night sky above you travel slowly westward during the year. Pinpoint a star you know well in the night sky at exactly 9 P.M. tonight. This same star will be in the exact same position in the night sky tomorrow night, only 4 minutes earlier, at 8:56 P.M. Check the time this same star is in the same position on the next night and you’ll see this occurs at 8:52 P.M.

Do a little math and you’ll verify that in one month this set up would leave the stars in the night sky 2 hours out of phase with our first positional reading in the night sky for this same star. In 3 months, generally one season, the stars in the night sky above you will have traveled a quarter of the way across the night sky. After four seasons, this would bring the star in question back to the same position in the night sky as twelve months before.

One way to estimate distances in the night sky above you and give yourself a tool to help you navigate the universe on your “Journey to the Beginning of Space and Time” is to use star pairs in the night sky as your guide. Star travelers can learn by using star pairs in the Big Dipper, for example.

Check out this astronomy site at http://astronomytonight.yolasite.com/, and then let me know what you think?

Learn how NASA astronomers are planning on detecting extraterrestrial moons orbiting distant suns https://spaceshipearth1.wordpress.com/2013/12/31/searching-for-extraterrestrial-moons/.

Read about the latest news on life beyond Earth https://spaceshipearth1.wordpress.com/2013/12/25/the-search-for-life-beyond-earth-takes-a-turn-at-jupiter/.

Take a look at the latest natural color images taken by the Cassini spacecraft https://spaceshipearth1.wordpress.com/2013/12/22/cassini-spacecraft-show-views-of-the-solar-system-in-natural-color/.

# Journey to Red and Orange stars in September’s night sky

## Fall is in full bloom in the Northern Hemispheres of planet Earth and lovers of the reds, oranges, and bright reds on the leaves of fall will enjoy the rich, warm and colorful hues in the night sky of September and October.

Astronomy News – If you’re heading out into the wild to enjoy Mother Nature’s bounty at this time of year? After a day walking through the forest watching the leaves on the trees turn color, from drab green to mixed shades of yellow, orange, and red. Take the time to lay back on the cold ground or your sleeping bag and check out the colors in the night sky. Even better, set up your binoculars or time machine to the stars, and enjoy the colors in the night sky by taking a journey to the beginning of space and time.”

Stargazers have witnessed the colorful displays in the night sky for generations and our ancestors surely spent many a night staring upwards in wonder at the various colors they could see in the night sky. It was 19th-century Irish astronomer John Birmingham, who first made note of the colorful hues of light in the night sky. His ideas and the thoughts of Danish astronomer Hans Schjellerup, who had compiled a catalog of red stars in 1866, were mentioned in Birmingham’s work “The Red Stars: Observations and Catalog”. This catalog contains a total of 658 red and orange stars colorful enough to delight the human senses and make your imagination dance a lively step.

Reading the introduction of Birmingham’s catalog of red and orange stars, one notes he mentions a region of space and time he refers to as “The Red Region”. This region includes parts of the Milky Way Galaxy, between Aquila, Lyra, and Cygnus, that are filled with orange and red stars that will make the eyes dance and entice the human imagination to create possibilities beyond anything we as humans have imagined.

## The colors of astronomy in September are a highlight amateur astronomers will love

September is the perfect time for you to board your time machine to the stars and journey to the beginning of space and time to experience the Red Region. The Red Region will be well above the southern horizon once the sun goes down. This region of space and time has eye-gems for stargazers to view in September, with reds and oranges that will make lovers of fall smile, and turn up their color sensitivity. The colorful stars in the Red Region warm sequentially through spectral classes: G (yellow), K (orange), M (red) and rare carbon class C (deep red). Astronomers have subdivided star classes from 0 to 9, with a G9 star being a little closer to orange than yellow, and a K5 star having a color somewhere between orange and red.

All-star gazers will see varying hues of red, orange, and yellow during their journey to the beginning of space and time that will depend on each star gazers own particular biology. In fact, we all view color slightly differently, so individual star gazers shouldn’t rely on a star’s spectral class for a visual clue to a star’s true color. Take, for example, the strikingly colorful, double star Albireo (Beta Cygni) in Cygnus. Stargazers through the centuries have described its magnitude 3.1 K3 primary star as yellow, topaz, gold and orange. Its magnitude 5.1 B9 (blue-white) secondary star (34″ away) on the other hand, has been described as deep-blue, azure, sapphire and even green.

The perception of color for humans is subjective and depends on varying individual parameters that can also be a product of physiological and psychological effects, such as the strong contrasting colors of a double star, like Albireo. The colors star gazers view through their time machine to the stars can also be obscured by dust and pollutants in the air, which will redden a star’s color. Stars that are low on the horizon, in comparison to higher stars, will also appear redder to viewers, just like the sun turns redder as it falls toward the horizon.

### Orange, red, and yellow hues abound in September

Read about NASA’s Messenger spacecraft and its mission to Mercury

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# Astronomy during September is amazing

## Astronomy News – Huddle around a campfire and journey to the stars –

The nights of September 2010 will feature essentially the same night sky as the one your ancestors used as a basis for many of the myths and stories that have been passed down to the modern world of today. September’s star gazers can sit huddled around the fire each night of the month, just as their ancestors did thousands of years in the past. The perfect time to board your time machine to the stars and take a journey through space and time or lay your back upon the cold earth and let the night’s sky open your mind to the possibilities of the universe.

The nights of September 2010 will feature essentially the same night sky as the one your ancestors used as a basis for many of the myths and stories that have been passed down to the modern world of today. September’s star gazers can sit huddled around the fire each night of the month, just as their ancestors did thousands of years in the past. The perfect time to board your time machine to the stars and take a journey through space and time or lay your back upon the cold earth and let the night’s sky open your mind to the possibilities of the universe.

## The Moon is one of the first places the human journey to the beginning of space and time visited

The Last Quarter Moon will step onto September’s celestial stage on September 1, at 1:22 P.M Eastern Daylight Time (EDT) and start September’s celestial dance. Heavenly Venus will join the dance at 2 P.M. EDT on September 1, as she passes to within about 1.2 degrees south of Spica and will form a line with Mars on one side and Spica spinning in the middle.

Mercury will be in inferior conjunction at 9 A.M. EDT on September 3. Mars will dance to within 2 degrees north of Spica at 10 A.M. EDT on September 4, but this dancing pair will slowly fade from view over the next few days, as the Moon moves closer to the Earth.

## Moon astronomy takes patience

The Moon will light up the night sky at 11:58 P.M. EDT on September 7. Earth’s satellite moves to within 221,948 miles of spaceshipearth1 on this date and the show on this night can light up the night sky. A New Moon will greet star gazers at 6:30 A.M. EDT on September 8 and on September 9 the moon will pass to within 8 degrees south of Saturn at 6 P.M. The celestial dance between Saturn and the Moon can light up your imagination as the Moon makes a pass by Saturn.

## Asteroid Flora will take astronomy lovers for a ride

Asteroid Flora will be in opposition on the tenth of September at 11 P.M. EDT. Asteroid Flora is a difficult celestial body to view for beginning stargazers. Should you desire to take a look at asteroid Flora at her finest on this night, it might be wise to obtain the help or advice of veteran stargazers in your search.

The Moon will also be dancing in the night’s sky on September 10. The Moon will pass to within 5 degrees south of Mars at 4 A.M. EDT and will then dance across the night sky and pass within 0.3 degrees south of Venus at 9 A.M. EDT.

Asteroid Laetitia will be in opposition on September 14 at 6 A.M. EDT. This is your chance to view a celestial body that has been entertaining star gazers and filling them with awe and wonder for thousands of generations.

The third week of September begins with a First Quarter Moon 1:50 A.M. EDT on September 15. Four days later, on September 19, Mercury will be at its greatest western elongation of 18 degrees at 1 P.M. EDT. The Moon will pass within 5 degrees north of Neptune at noon EDT on September 20, viewers should see both Neptune and the Moon in the night sky, but this will depend on environmental conditions at the time of viewing.

Asteroid 8 Hebe is at opposition at 2 A.M. EDT on September 21. The thirteenth biggest asteroid by mass in the known solar system and the fifth brightest celestial body in the asteroid belt, asteroid 6 Hebe is believed to be the source of H chondrite meteorites and IIE iron meteorites, which account for about 40 percent of the meteorites that land on Earth.

The Moon is at apogee (252, 379 miles from Earth) at 4:02 A.M. EDT on September 21. Apogee is the point at which the Moon is at its farthest distance from the Earth in its orbit.

Mighty Jupiter rules the night on September 21, the largest planet in our solar system will be in opposition at 8 A.M. EDT on this day and Neptune will follow into opposition at 1 P.M. EDT. Jupiter shines at magnitude 2.9 on this night and will look bigger visually than at any time since October 1963, at about 49.9 ” across.

## Astronomy royalty takes center stage

Jupiter will still be one of the brightest celestial objects in the night sky on September 22 and viewers should be able to get a great view of mighty Jupiter in all its glory using their time machine to the stars throughout the month. Jupiter will pass within 0.9 degrees south of Uranus on September 22, at 3 P.M. EDT, and this is a great time to take a look at two of the biggest celestial bodies in the solar system. Watch for a few hours, before Jupiter passes to within 0.9 degrees south of Uranus, and you can see the Earth enter autumnal equinox at 11:09 P.M. EDT.

A Full Moon will occur at 5:17 A.M. EDT on September 23. The Moon will travel toward Neptune and Jupiter during the next hour and forty-five minutes and will pass within 7 degrees north of Jupiter and 6 degrees North of Uranus at 7 A.M. EDT. Viewers that watch throughout the day will get to see Venus at her brightest at 4 P.M. EDT, at this time, Venus will shine at magnitude 4.8, the perfect time to view demure Venus in September’s night sky.

## Venus, for lovers, and unforgettable astronomy

Venus is once again the main attraction on the night of September 29. Venus will pass within 6 degrees south of Mars at 2 A.M. EDT on this night and will shine bright enough for good viewing using your time machine to the stars or good viewing binoculars.

September 30 will see Saturn enter into conjunction with Sol, at 9 P.M. EDT. This is a great opportunity to view the ringed planet and view a celestial body that has fascinated the human imagination for generations. Keep watching until 11:52 P.M. EDT and you’ll see the Last Quarter Moon appear in the night sky at 11:52 P.M. EDT.

### Astronomy continues next month

Read about the present news on the search for life beyond Earth https://spaceshipearth1.wordpress.com/2013/12/25/the-search-for-life-beyond-earth-takes-a-turn-at-jupiter/.

View the latest in high definition images of the solar system provided by NASA’s Cassini spacecraft https://spaceshipearth1.wordpress.com/2013/12/22/cassini-spacecraft-show-views-of-the-solar-system-in-natural-color/.

We tell you about the astronomy highlights upcoming for 2014 https://spaceshipearth1.wordpress.com/2013/12/19/2014-the-journey-ahead/.

# September astronomy rocks!

Astronomy News – September is one of the year’s most entertaining and awe-inspiring months to lay on your back on a dark hill and view the delights of the celestial dance in the sky as your ancestors did on a nightly basis. Four of Sol’s dance partners will be in the spotlight in September 2010, taking part in a nightly dance that includes their less observable brothers and sisters, while Mercury will once again dance privately in the eastern sky each morning during September.

## Mighty Jupiter is astronomy royalty

Mighty Jupiter will rule the night’s sky in the Northern Hemisphere during September, especially after he reaches the point in his orbit opposite the sun as seen from SpaceshipEarth1, which space scientists call Jupiter’s opposition. This celestial event will occur on the last day of summer in the Northern Hemisphere, on this day the 24 hour period of the day will be evenly separated into night and day, and the evening temperature will still be warm enough to make star-gazing comfortable. The perfect time to set up your celestial time machine to the stars or to just lay back on the cold Earth and watch the celestial dance above you unfold before your eyes as millions of your ancestors have since mankind first perceived the possibilities the night’s sky creates in the human imagination. This will be the most comfortable and best time to view Jupiter in the past 47 years and it will definitely be more comfortable viewing than during Jupiter’s next opposition on October 29, 2011. During Jupiter’s opposition on October 29, 2011, the weather will be a lot of colder than on September 21, 2010, and you’ll have to wait another year to have a look at the largest planet in our solar system.

Mighty Jupiter will be at his brightest when he reaches opposition on September 21, 2010, on this night the King of Sol’s planets will shine brighter in the night’s sky than during any time in the past 47 years. Jupiter will also appear bigger during its September 21, 2010, opposition, subtending an angle of almost 50 “, and shining at magnitude 2.9. This means that after Venus sets at around 8 P.M., mighty Jupiter will be the brightest star-like object in September’s night sky.

## Astronomy is for lovers

Mighty Jupiter will travel near the border between the constellations of Aquarius and Pisces for several months on both sides of opposition. This region of space-time has few bright stars to outshine Jupiter and the contrast allows viewers to get a good look at Jupiter. The nearest 1st magnitude star, Fomalhaut (Alpha) Piscis Austrini, is over 30 degrees away and mighty Jupiter is easily observed in the night’s sky at this time.

Stargazers in the mid-northern latitudes will find that due to their location mighty Jupiter only climbs halfway up the night’s sky in September 2010. This doesn’t make for the best viewing during Jupiter’s opposition and Jupiter’s altitude will be at its greatest at local midnight time. Stargazers at latitude 40 degrees north will see Jupiter at 48 degrees above the southern horizon. In the northern hemisphere of Earth, star gazers will view Jupiter 1 degree higher in the night’s sky, for each degree of latitude south of 40 degrees north at which they’re viewing Jupiter. In contrast, for each 1 degree north of 40 degrees north at which you observe Jupiter, you’ll see Jupiter 1 degree lower in the night’s sky.

Stargazers that want to view mighty Jupiter as he dances across September’s night sky can so without a pair of binoculars. Stargazers will need a pair of binoculars or telescope to see Uranus, Sol’s seventh planet will lie within 2 degrees of Jupiter throughout September, and can be difficult to view Uranus at this time. Sol’s eighth planet, Neptune, will be found about 30 degrees west of Jupiter and Uranus during September. Stargazers that want to view Venus and Mars should look in the evening twilight near Virgo’s brightest star, Spica.

## Planet astronomy is exciting and something that fills a young mind with awe

We’ll begin our journey across September’s night sky during the first week of Earth’s ninth month, Saturn will be dancing in the twilight of the low horizon of September’s night sky. We’ll board our time machine to the stars and planets on September 1 and start the first leg of our celestial “Journey to the Beginning of Time and Space” in human terms by traveling across space and time to Saturn. Sol’s ringed planet will set an hour after the sun on this day and can be found dancing in the sky about 5 degrees above the horizon after the sun goes down.

To locate Saturn, use Venus as your visual guide. Earth’s evening star will be visible a few minutes after the sunsets. Look for Spica in the constellation Virgo, to the right of Venus. Saturn and Spica glow at the same relative magnitude, so if you take your time and can find Spica, you should be able to see Saturn in the night’s sky above you. Saturn will be found 20 degrees to the right of Venus in September’s night sky and at around half the distance from the horizon as Venus. Saturn will continue to be viewable from Earth, throughout the first week of September 2010, and observing Saturn from SpaceshipEarth1 will become increasingly difficult after this time.

On September 1, 2010, Venus will be dancing in the night’s sky in line with Spica and Mars. Spica will be in the middle of this dance, and if you continue to watch this celestial dance unfold for two more nights, Spica will dance toward the center of the trio. The trio will begin to fall back from each other as September enters the second week and will form an ever-widening triangle. Venus will shine the brightest during this celestial dance across September’s night sky while Spica will outshine Mars as the trio does their nightly dance across the skies of September.

On September 10 a crescent moon will join this celestial dance. Mars will be viewable about 6 degrees above the Moon while Venus will be to the lower left of Mars. Continue to watch this dance unfold and you’ll see the Moon travel 6 degrees to the left of Venus by the time September 11, 2010, arrives. The Moon will also grow in visible size each night after September 11, 2010, until reaching full moon at 5:17 A.M. EDT on September 23.

## Venus is one of the most recognized planets of astronomy

Venus will continue to be viewable in September’s night sky as she dips closer to the horizon each night during September. Venus will shine her brightest on September 23, 2110, when the evening star will shine at magnitude 4,8 and will set an hour after Sol retires for the night. Watch Venus during this time and she’ll draw you into her nightly dance and fascinate you as she goes through obvious changes in visible size and phase. View Venus on September 1 and you’ll see a planet with a disc 29 ” across and at 41 percent illumination. By the time the dance reaches September 30, Venus has slimmed to 19 percent illumination and swelled to about 45 “, a change that can be easily discerned by patient stargazers.

Mars will appear small and dim compared to the Evening Star, the Red Planet will shine at magnitude 1.5 throughout September 2010, which is around 300 times dimmer than Venus will shine. Mar’s disk also measures only 4″ and very little detail will be seen by viewers looking at Mars through a telescope. Mars will become more visible late in 2011, so if you want to have the best view of Mars, you’ll have to wait until this time.

September will be a great time to view Sol’s ninth planet though as Pluto will dance an elegant loop in northwestern Sagittarius, close to an 8th magnitude star that’s only 2.6 degrees north-northwest of 4th magnitude Mu Sagittarii. This will make this 14th magnitude dwarf planet, which some claim isn’t really a planet, easier to view due to its proximity to this relatively bright star. You’ll still require an 8-inch telescope and a dark sky to be able to see Pluto in September’s night sky, but the view is spectacular, and you can get a good idea of the distance involved.

### Astronomy is in the human soul

Read about the present news on the search for life beyond Earth https://spaceshipearth1.wordpress.com/2013/12/25/the-search-for-life-beyond-earth-takes-a-turn-at-jupiter/.

View the latest in high definition images of the solar system provided by NASA’s Cassini spacecraft https://spaceshipearth1.wordpress.com/2013/12/22/cassini-spacecraft-show-views-of-the-solar-system-in-natural-color/.

We tell you about the astronomy highlights upcoming for 2014 https://spaceshipearth1.wordpress.com/2013/12/19/2014-the-journey-ahead/.