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Thread: The Astronomy Thread

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    Lightbulb The Astronomy Thread


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    Welcome to the Astronomy Thread!
    Every week we will be posting tips on what you can see in the night sky.
    Most of them will require no telescope or binoculars.
    We will also be discussing astronomy news and ways of improving observations.
    The times and days given, unless otherwise stated, are for North America. But as we grow, we hope also to be able to provide information for those in Eurasia and eventually the Southern Hemisphere.


    The current observing tips will always be at the top of the thread but older tips will be archived further down.


    Week of 27 November 2005

    Occasionally it is possible to see a planet during the daytime. But you do have to know exactly where to look.
    Before dusk on Sunday December 4th, you should have no trouble spotting the crescent moon. If you look carefully, you should also be able to pinpoint Venus to the right and slightly higher than the moon. Eventually Venus will fade into view. By half an hour after sunset Venus is so bright that most casual observers would probably mistake it for an approaching aircraft.




    There is frequently confusion over what is meant by the term constellation.
    In 1930 the International Astronomical Union adopted a plan developed by Belgian astronomer Eugène Delporte which divided the sky into 88 official constellations. Every object (star, galaxy, nebula, etc.) within the boundaries of each constellation was considered part of that constellation. So every square degree of the sky is part of some constellation.
    A list of the 88 official constellations, including their standard three-letter abbreviations and other info, can be found here and here.

    An asterism is any group of stars that forms a pattern in the sky. The Summer Triangle is a very large asterism. The Teapot (in Sagittarius) is a well defined one in a wonderfully rich part of the sky. Asterisms can be very subjective. There's nothing to prevent you from making up your own. Perhaps the stars in Capricornus look a little like a bikini bottom, or the stars in Orion resemble a cell phone.

    To help demonstrate the distinction between a constellation and an asterism, here is a chart for the constellation Ursa Major.



    Everything within the borders of Ursa Major is part of that constellation. However, the most recognizable part of that constellation is the asterism known as The Big Dipper. So the Big Dipper just forms a part of Ursa Major.


    To look at this another (more down to earth) way, here is a map of Kiribati in the South Pacific.


    Every island within the broken lines that form the international boundary is part of the Republic of Kiribati. But various islands in Kiribati can be lumped together to form groups. So Kiribati would be the equivalent of a constellation and the Gilbert Islands the equivalent of an asterism.


    QUOTE=Astro
    Since I think I've already done a blurb on Venus there isn't much more for em to say, so I'm going to not comment on that portion.

    As for constellations and asterisms, do not get the two mixed up....or you shall face my wrath .

    Like Optid said, a constellation is the OFFICIALLY INTERNATIONALLY RECOGNIZED star 'formation' in the sky. There are 88 of them in total, and they span the entire sky. An asterism is just a shape that you can see in the stars. 3 famous asterisms are the Big Dipper, the Teapot, and the Summer Triangle. There are an infinite number of asterisms because they are just what people see. I myself have a few unique ones that only I have heard off because I assume I'm the only one to ever think of them.
    /QUOTE
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    Default Re: The Astronomy Thread

    This has been a long time in planning between Optid and myself. I am happy to see it finally here.

    First off, I'd like to just list some books that I find fascinating for the beginner (or n00b) to astronomy. Sorry for the length.

    <?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o:p></o:p>

    1) Nightwatch – Terence Dickinson

    This is a great book for any beginner. It perfectly explains all of the basic astronomical info, such as planets, the universe in 11 steps, backyard astronomy, telescopes and accessories, stars, galaxies, and the solar system. This book is my bible. It also contains some great star atlases in it. They are some of the most helpful ones I have ever seen. I highly recommend this book to any person who is interested in astronomy. I actually own 2 copies of it.
    <o:p></o:p>

    http://www.chapters.indigo.ca/item.asp?Item=978155209302&Catalog=Books&Ntt=Night watch&N=35&Lang=en&Section=books&zxac=1


    2) The Backyard Astronomer’s Guide – Terence Dickinson and Alan Dyer

    This book is similar to Nightwatch, but it goes into much more detail on backyard astronomy. It has an excellent section on telescopes, it explains each type, and even shows you how they work, complete with diagrams. There is also a large section on accessories, which is again fantastic. There are also chapters on how to observe the planets, galaxies, nebulae etc…There is also a fantastic section on astrophotography. This section is somewhat dedicated to film astrophotography, but it is a GREAT tool. I learnt almost all my knowledge from this section. Along with Nightwatch, these 2 books are all any backyard or amateur astronomer can hope for.

    http://www.chapters.indigo.ca/item.asp?Item=978155209507&Catalog=Books&Ntt=Backy ard+Astronomers+Guide&N=35&Lang=en&Section=books&z xac=1


    3) StarWatch – Philip S. Harrington.

    This book is for the more advanced backyard astronomer. It gives the location of all 109 Messier objects, and some of the most famous NGC objects. Along with these, there are instructions on how to find it, and what they look like through binoculars, small, and large telescopes. This is a great field guide to finding you’re favourite DSO’s.
    <o:p></o:p>

    http://www.chapters.indigo.ca/item.asp?Item=978047141804&Catalog=Books&Ntt=Star+ Watch&N=35&Lang=en&Section=books&zxac=1


    4) Bad Astronomy – Dr. Plait

    Are you sick and tired of all the astronomical myths out there? Are you a victim of astronomical pseudo-science? If you are then this book is for you. It covers some of the most common myths in astronomy, and it discusses some pseudo-science, including astrology. This book compliments his website www.badastronomy.com and is a fun read for everyone.

    http://www.chapters.indigo.ca/item.asp?Item=978047140976&Catalog=Books&Ntt=Bad+A stronomy&N=35&Lang=en&Section=books&zxac=1


    5) Astronomy for Dummies – Stephen P. Maran

    I know, yet another book in the Dummy series. This is a fantastic book that describes the basics of astronomy to anyone. It uses the traditional easy to learn “Dummy” style that is present in all the books.

    http://www.chapters.indigo.ca/item.asp?Item=978076458465&Catalog=Books&Ntt=Astro nomy+for+Dummies&N=35&Lang=en&Section=books&zxac=1

    <o:p></o:p>
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    Default Re: The Astronomy Thread

    QUOTE=optid
    Welcome to the Astronomy Thread!
    Every week we will be posting tips on what you can see in the night sky.
    Most of them will require no telescope or binoculars.
    We will also be discussing astronomy news and ways of improving observations.
    The times and days given are for North America. But as we grow, we hope also to be able to provide information for those in Eurasia and eventually the Southern Hemisphere.

    The current observing tips will always be at the top of the thread but older tips will be archived further down.



    Week of 10 July 2005

    If you'd like to see Jupiter, the moon makes it easy to spot this week in the southwest.. The moon moves from about 9 degrees to the right of Jupiter on the evening of Tuesday the 12th to 3 degrees the left of Jupiter on Wednesday evening the 13th. Jupiter will be the brightest object near the moon on those nights, there is little chance of mistaking anything else for Jupiter. If you have a pair of 7 X 50 (or better) binoculars, you can see as many as four of Jupiter's moons, the same ones that got Galileo in trouble.

    Between the 13th and 14th the moon passes near Spica, a bright bluish-white star over 260 light years away.



    BTW, Venus is still visible about an hour after sunset just over the WNW (west-northwest) horizon.
    /QUOTE

    Here is what it will look like on the date of July 12.



    This is looking west. If you have access to a telescope then I would highly reccommend taking a gander towards Jupiter. if you've never been able to find the planet this is your perfect chance. It will be the next brightest object near the Moon. Now, if you do look at it through a telescope, don't be discouraged if you only see a grey dot. Take your time, and eventually some subtle features will appear. Even the smallest telescopes will reveal Jupiters 4 largest moons, and the 2 equatorial belts.

    These are the best times to find a planet. This is how I first found Jupiter and Saturn. I waited for the moon to get close to it and then I used the moon to guide myway to the planet. Its a great chance for anyone out there with clear skies to learn a thing of two.
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    Default Re: The Astronomy Thread

    Quote Originally Posted by Astro

    <?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o:p></o:p>

    1) Nightwatch – Terence Dickinson

    This is a great book for any beginner. It perfectly explains all of the basic astronomical info, such as planets, the universe in 11 steps, backyard astronomy, telescopes and accessories, stars, galaxies, and the solar system. This book is my bible. It also contains some great star atlases in it. They are some of the most helpful ones I have ever seen. I highly recommend this book to any person who is interested in astronomy. I actually own 2 copies of it.
    <o:p></o:p>


    <o:p></o:p>


    excellent book






    For the ppl who don't know me I'm a astronomy wacko who works at an observatory/planetarium. I am a decently experienced amateur astronomer with strong interests in astrophotography (Astro can tell u that ). I will post some awesome pics when they approve me using our new SBIG CCD camera at the abservatory (god takes them forever lol ). My ongoing project is observing all the Messier objects that I can see. Hopefully tonight I will add M4 to by list, being a bright Globular cluster near Antares...for some reason I forgot about this one when I was observing all the globulars one night. I'll make a full list of things I;ve observered it I get bored some day .


    Here is my famous Saturn pic i took with a B&W video camera @ 675x magnification:

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    Default Re: The Astronomy Thread

    Not knowing much about this region of space I can't really add anything to this weeks news, but I have something to add.


    On the day of July 21 the Full Moon will appear 9% larger than the Full Moon on December 15. On this date, the Moon reaches perigee, which is the cloest point the moon will make to Earth on this revolutin around the Earth. This perigee is also special because it is also when the moon makes its closest appraoch to the Earth of 2005, it will be 357,159 km away opposed to 405,013 km in December. The opposite of perigee, is apogee, which is when the moon is at its furthest point from the Earth for the month.


    If I can get a chance, I may try to take my camera outside and take a few pics of the Antares region, just so you can get a glimpse of what it looks like.

    If you have a pair of binoculars then I would take Optid's advice and scan this area. There are lots of stunning targets in this area of the sky. 2 notable objects are M4, and M80, both of which are near Antares. Through a pair of binoculars you should be able to see he faint glow if M4 as a tiny, undefined smudge of greyish light just to the west of Antares. For M80 you will see (given dark skies) the disc that belongs to M80. At first it may look like just another point of light set in a dense star field, but if you concentrate long enough you should see a round, softly glowing disc highlighted by a more intense centre



    QUOTE=optid
    Week of 17 July 2005

    The moon continues to act as a guidepost to other objects in the sky.
    On the evening of Sunday July 17th, the moon passes very close to the star Antares.
    In the Northern Hemisphere, just look south about 1.5 hours after sunset.

    From the U.S. South to the northern part of South America, the moon will actually
    pass in front of Antares.
    When the moon temporarily blocks our view of a planet, star, or asteroid, it is called an occultation. But an occultation has absolutely nothing to do with the occult!
    One of the cool things about an occultation, or even a "near occultation" is that you get a sense of the real time motion of the moon in the sky.

    This chart will give you some idea of which U. S. cities will see the occultation and which will have a near miss. Generally, the further south you are, the more likely you will see it.


    Antares is a fairly bright star located about 600 light years away. It is a red
    supergiant that is 300 times the diameter of the sun. It appears distinctly red-orange.
    Antares is located in a particularly rich part of the Milky Way.
    Now that you know where it is, check out this region of the sky with binoculars. /QUOTE
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    Default Re: The Astronomy Thread

    Quote Originally Posted by Astro


    If you have a pair of binoculars then I would take Optid's advice and scan this area. There are lots of stunning targets in this area of the sky. 2 notable objects are M4, and M80, both of which are near Antares. Through a pair of binoculars you should be able to see he faint glow if M4 as a tiny, undefined smudge of greyish light just to the west of Antares. For M80 you will see (given dark skies) the disc that belongs to M80. At first it may look like just another point of light set in a dense star field, but if you concentrate long enough you should see a round, softly glowing disc highlighted by a more intense centre
    I have Uber-light pollution...can't even see M4 with bino's ...only with a scope.....esp M80.....u know M80 is a globular cluster right....ur descriptions sounds like a galaxy lol .......that region of the sky has alot of good stuff esp near the "teapot"....M8 (lagoon nebula) and various open clusters

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    Default Re: The Astronomy Thread

    Quote Originally Posted by carman2003
    I have Uber-light pollution...can't even see M4 with bino's ...only with a scope.....esp M80.....u know M80 is a globular cluster right....ur descriptions sounds like a galaxy lol .......that region of the sky has alot of good stuff esp near the "teapot"....M8 (lagoon nebula) and various open clusters
    I took the descriptions from one of my books. I know its a globular cluster, and I probably should've stated that, but as it was close to 2 AM when I wrote it I guess I wasn't thinking clearly. I think another reason I didn't state that was because we are trying to keep this thread jargon free, so mentioning globular clusters right away may just be a little too much at once.

    I think I should also point out that neither of those objects are really spectacualr. But since they were so close to Antares they were worth mentioning. If you are comfortable enough with binoculars than I will definetly reccommend looking in the teapot region (I'll post a diagram when I get time) and in there are some of the best sights of the summer skies.
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    Default Re: The Astronomy Thread

    QUOTE=optid
    Week of 24 July 2005

    The Summer Triangle is one of the most prominent asterisms (star patterns) visible in the Northern Hemisphere.

    While it can also be seen in spring and fall, this trio of stars is especially well placed for prime time viewing during the northern summer.

    The bright stars that make up the triangle are: Vega, Deneb, and Altair.
    Altair is 17 light years away from us. If you are 17 years old, the light you see from Altair left that star around the time you were born.
    Vega, the brightest of the three, is 26 light years away. It was featured in the 1997 film "Contact".
    Deneb is about 1,500 light years away and is one of the most massive stars we know. It is 25 times the mass and 60 times the diameter of our sun.

    The Summer Triangle takes up more than twice as much space as the Big Dipper. So when you look for it, think BIG.
    I think the Summer Triangle is actually easier to spot in light polluted cities and suburbs than out in the country. Only the brightest stars show up in urban skies and the stars of the Summer Triangle are among the forty brightest you can see from Earth.

    Here's a chart to help you find the triangle in the east after sunset for the next few weeks.



    BTW, if you live in a light polluted area, don't worry about the "dust cloud" or the Milky Way. You probably can't see them.

    Another way to spot the Summer Triangle is to look for it around 11:00 PM. At roughly that time, Vega, at least for those of us who live between 35° and 50° North latitude, will be almost directly overhead. In Northern Illinois it will be slightly south of that. Once you find Vega, locating the other stars of this isosceles triangle should not be too difficult.

    Here's another chart. Remember that Altair points away from Polaris (The North Star).



    /QUOTE

    As another anouncement, Mars is now visible in the morning sky. I saw it for the first time last week around 3 am, and it was a nice sight to see. I can't wait to get my telescope out. Mars is easy to identify. Just look for the bright red "star". Right now it spends most of the morning in the Eastern Sky. Even through a pair of binoculars Mars should show some surface detail, I think.

    On Wednesday, the 27th, Mars and the Moon will be close together. This is a great opportunity to find Mars, if you were unable to do so earlier.



    As an ammusing annecdote, over the weekend I was talking with some friends who went stargazing one night, and one of them shouted out, "look at the triangle" and the other replied "You can see the Bermuda Triangle?" I found it to be hilarious, even though it doesn't seem to funny here.

    I think the summer triangle is something that people who live with light pollution should be happy for. It is easy to spot. Tonight I looked up at the sky, and it took me a minute to find it with all the other stars out there, I must admit that i got lost. Here (45 degrees North) at 11:00 PM Vega is pretty much right above me, so it should be relatively easy for most people to find it.

    I will post more when I get a chance to.
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    Default Re: The Astronomy Thread

    I look forward to checking this thread regularly. Anyone interested in Astronomy might want to check out http://skyandtelescope.com/ It's an interesting site on the subject and offers the latest news in Astronomy.


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    Default Re: The Astronomy Thread

    I went out last night for a little bit of observing and photography. I took my first views of the Lagoon Nebula (M8 )through my 10" for the first time and I almost fell off my stool. It was so nice. I could see so much detail! Unfortuntly the clouds rolled in about 10 minutes later, so I didn't get any time to realy observe it. I also took some pics of the Big Dipper (only thing that wasn't obstructed by clouds) and I'll post them as soon as I find time. I'll also post a pic of where the Lagoon Nebula is located, if anyone with binoculars or a telescope decides to check it out.
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    Default Re: The Astronomy Thread

    The Big Dipper:



    To find M8, all you do is look for the teapot asterism (non official constellation) and move a little but aways from the top most star. Here are 2 pics of it.



    Do you see the teapot?

    If not, here it is with it drawn in.

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    Default Re: The Astronomy Thread

    I have returned!

    I finally wrote something over my vacation that I have been meaning to write for a month or so now. Optid, sorry for the delay.

    When I get a chance I will post some pics to go along with this. I hope it makes sense.

    This has been something that we have been planning to for a while now, but I’ve been so busy that I’ve just been able to get to this now. Here I am, on vacation, no Internet access, no phone lines, no nothing, and I’ve still got this thread on my mind. Since I’m bored I might as well get this written.

    <?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o:p></o:p>

    Like I said, this is something that I’ve been planning to write for a long time,. And I’ve just finally found the time to do this.

    <o:p></o:p>

    Optid and I are trying to keep this thread as jargon free as possible, but this is one concept that we have to introduce. Angular sepreation. In astronomy, we measure the apparent distances between objects in degrees, minutes and seconds. The high the degree is, the farther apart the objects are. For example, the angular seperation between Alkaid (the last star of the Big Dipper’s “handle”) and Merak (the lower right star of the bowl) is 25<SUP>o</SUP>33’50” (25 degrees 33 minutes and 55 seconds). Two objects with an angular separation of 10<SUP>o</SUP> are closer than 2 objects with an angular separation of 37<SUP>o</SUP>.

    <o:p></o:p>

    We will probably only be using angular separation when we announce the distance between the Moon, and a nearby planet or star. A crude, simple method of measuring angular separation is by using your hand held at arms length from your body. The distance between your pinky and your thumb, at arms length away, roughly represents a distance of 25<SUP>o</SUP> (or the distance between Alkaid and Merak) the distance between your index finger and pinky at arms length is approximately 15<SUP>o</SUP>, or the distance between Alkaid and Megrez (the star joining the “handle” and “bowl” of the Big Dipper).






    Unfortuntly, I don't really have anything to add this week. Optid pretty much stated all of it. Don't worry too much about confusing Jupiter and Spica, as far as I remember, Jupiter is the brighter of the two.
    <o:p></o:p>

    QUOTE=optid Welcome to the Astronomy Thread!
    Every week we will be posting tips on what you can see in the night sky.
    Most of them will require no telescope or binoculars.
    We will also be discussing astronomy news and ways of improving observations.
    The times and days given, unless otherwise stated, are for North America. But as we grow, we hope also to be able to provide information for those in Eurasia and eventually the Southern Hemisphere.

    The current observing tips will always be at the top of the thread but older tips will be archived further down.



    Week of 31 July 2005

    There's an astronomy mnemonic which goes, "Follow the arc to Arcturus and then the spike to Spica." This is an easy way to find two bright colorful stars.

    Just about everybody in the Northern Hemisphere is familiar with the asterism (star pattern) called the Big Dipper. It resembles a pot with a curved handle.
    Now pretend that the "handle" has three additional stars in it which continue the curve. Those "fictional" stars would take you right up to the orange giant Arcturus.
    Go from Arcturus in a straight line towards the horizon but a bit to the right. That should take you to the blueish white star Spica. Spica is roughly the same distance in the sky from Arcturus as Arcturus is from the last star of the handle of the Big Dipper. Spica is relatively low in the sky in mid-northern latitudes (the U.S., Southern Canada, Europe, Russia, Japan, and Northern China). So you'll need a clear view of the horizon to see it.

    Arcturus is about 36 light years away from us, not terribly far by galactic standards. Spica is roughly 270 light years away.

    Be careful not to confuse Spica with the planet Jupiter, which is currently about 10° away from Spica.
    Spica has a slight bluish tint to it, Jupiter does not.

    This chart should help a bit.



    The New Moon occurs on Thursday August 4th at 10:05 PM Central Daylight Time (that's Friday August 5th at 0305 GMT).
    BTW, if you'd like the rising and setting times for the sun or moon for any given day, you can get them from the U.S. Naval Observatory...
    http://aa.usno.navy.mil/data/docs/RS_OneDay.html


    NOTE: Astro is on vacation. He will return late this week.

    _________________________
    Next Week: The Perseid Meteor Shower
    _________________________/QUOTE

    <o:p></o:p>
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    Default Re: The Astronomy Thread

    There isn't a whole lot to add this week, Optid pretty much summed it all up.

    The Perseids are one of the best meteor showers of the year. It was actually the first one I'd ever seen. On a good year, under a dark sky, you can even see 1 meteor a minute, or more!

    If you have a camera with a Bulb (B) setting, and shutter release cable, I would say point the camera towards Perseus witha wide angle lens (28mm or fisheye) and open the shutter for a few minutes. In that few minutes I'm sure you could get some awsome pics. I'm actually going to try and get some of them this year.

    QUOTE=optid
    Welcome to the Astronomy Thread!
    Every week we will be posting tips on what you can see in the night sky.
    Most of them will require no telescope or binoculars.
    We will also be discussing astronomy news and ways of improving observations.
    The times and days given, unless otherwise stated, are for North America. But as we grow, we hope also to be able to provide information for those in Eurasia and eventually the Southern Hemisphere.

    The current observing tips will always be at the top of the thread but older tips will be archived further down.



    Week of 07 August 2005

    The Perseid meteor shower occurs on August 11th-13th. It's peak is predicted to be at 1700 GMT on the 12th. That favors our friends in Asia and Australia. But because the Perseids are so abundant, you can see a reasonable number of meteors within roughly 18 hours of the peak.
    In North America, the best time to watch is probably on the night of the 11th/12th from midnight until an hour before sunrise. The moon will have set by then. And after midnight, our part of Earth turns into the stream of meteors, making collisions with them more likely.

    Meteors are created by passing comets which leave behind a diffuse stream of debris. The Perseid meteor shower takes place when Earth passes through the debris field left behind by Comet Swift-Tuttle.
    Meteors are actually very small. Most are the size of grains of sand. The bigger ones may be as big as pebbles. Close to all burn up in the atmosphere before they can strike the ground.

    To get a good look at the Perseids, you need to be in a place without a lot of light pollution. If the sky is dark enough for you to see the Milky Way, you are in a good location. There you should be able to see a meteor every couple of minutes. But even in light polluted areas, you should be able to see a few of the brighter Perseids.

    Watching a meteor shower requires no expertise and no special equipment. Just find a good location with as little light pollution as possible and observe. A comfortable lawn chair is recommended.
    If you do drive out to the country, ALWAYS bring an extra sweatshirt or light jacket. Nights are colder out in the country than in major urban areas.

    The Perseids get their name from the constellation Perseus. From our perspective, the meteors are seen as originating from the portion of the sky occupied by Perseus. However a lot of the meteors won't become visible until they are relatively far from Perseus in the sky.
    Perseus is in the east around midnight and slowly moves clockwise with everything else in the sky.
    So always keep one eye on the east, but do not ignore the rest of the sky.

    One of the brighter Perseid meteors



    The Perseids aren't enough for you this week?
    Wait, there's more!!!

    If you missed the moon's pass near Jupiter last month, the two have another rendezvous on the evening of Tuesday the 9th.



    That chart above does not show it, but on the evening of Wednesday the 10th Jupiter passes very close to the bright bluish-white star Spica./QUOTE
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  14. #14
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    Default Re: The Astronomy Thread

    Here is a good article about the Persieds I found on spece.com

    <TABLE border=0><TBODY><TR><TD vAlign=top align=left width=355>Viewer's Guide: Perseid Meteor Shower Peaks Aug. 12


    By Joe Rao
    SPACE.com Night Sky Columnist
    posted: 05 August 2005
    06:25 am ET


    </TD></TR></TBODY></TABLE><STYLE type=text/css><!--.style1 { font-family: Arial, Helvetica, sans-serif; font-size: 12px;}.style2 {font-family: Arial, Helvetica, sans-serif; font-size: 12px; font-weight: bold; }.style3 {font-family: Arial, Helvetica, sans-serif}.style4 {font-size: 12px}--></STYLE>
    Every August, when many people go vacationing in the country where skies are dark, the best-known meteor shower makes its appearance.

    It is also the month of "The Tears of St. Lawrence."

    Laurentius, a Christian deacon, is said to have been martyred by the Romans in 258 AD on an iron outdoor stove. It was in the midst of this torture that Laurentius cried out:

    "I am already roasted on one side and, if thou wouldst have me well cooked, it is time to turn me on the other."

    The saint’s death was commemorated on his feast day, Aug. 10. King Phillip II of Spain built his monastery place the "Escorial," on the plan of the holy gridiron. And the abundance of shooting stars seen annually between approximately Aug. 8 and 14 have come to be known as St. Lawrence’s "fiery tears."

    What to expect

    In 2005, the Perseids are expected to reach their maximum on Aug. 12. Peak activity is unfortunately predicted for the daylight hours across North America. Sky watchers are thus encouraged to watch during the predawn hours of Friday, Aug. 12 and again during the early morning hours of Saturday.

    Observers will be favored by an absence of bright moonlight during these intervals. At midnorthern latitudes, moonset occurs on the evening of Aug. 11 at around 11-p.m. local daylight time and around 11:20 p.m. the following night. Since dawn doesn’t break until around 4:30 a.m., that means there will be about 5 to 5½ hours of dark, moonless skies for the two best viewing nights for the Perseids.

    Take full advantage of this year’s favorable lunar circumstances. Next year, a bright waning gibbous Moon will flood the after-midnight sky with its light and seriously hinder the Perseids.

    Bits of a comet

    We know today that these meteors are actually the dross of the Swift-Tuttle comet.

    Discovered back in 1862, this comet takes approximately 130 years to circle the Sun. And in much the same way that the Tempel-Tuttle comet leaves a trail of debris along its orbit to produce the Leonid Meteors of November, Comet Swift-Tuttle produces a similar debris trail along its orbit to cause the Perseids.

    Indeed, every year during mid-August, when the Earth passes close to the orbit of Swift-Tuttle, the material left behind by the comet from its previous visits, ram into our atmosphere at approximately 37 miles per second (60 kilometers per second) and create bright streaks of light in our midsummer night skies.

    Comet Swift-Tuttle made its most recent appearance more than a dozen years ago, in December 1992. Its orbit is highly elongated and as such it takes roughly 130 years to make one trip around the Sun. For several years before and after its 1992 return, the Perseids were a far more prolific shower, appearing to produce brief outbursts of as many as several hundred meteors per hour, many of which were dazzlingly bright and spectacular.

    The most likely reason was that the Perseids parent comet was itself passing through the inner solar system and that the streams of Perseid meteoroids in the comet’s vicinity were larger and more thickly clumped together. Hence the reason for the brighter meteors and much-higher-than-normal meteor rates.

    In recent years, with the comet now far back out in space, Perseid activity has apparently returned to normal.

    Meteor clumps

    A very good shower will produce about one meteor per minute for a given observer under a dark country sky. Any light pollution or moonlight considerably reduces the count.

    The August Perseids are among the strongest of the readily observed annual meteor showers, and at maximum activity nominally yield 50 or 60 meteors per hour. However, observers with exceptional skies often record even larger numbers.

    But while 60 meteors per hour correspond to one meteor sighting every minute, keep in mind that this is only a statistical average.

    In reality, what usually is seen is what some have called, "the clumping effect." Sometimes you’ll see two or even three Perseids streak across the sky in quick succession, all within less than minute. This is usually followed by a lull of several minutes or more, before the sky suddenly bears fruit once again.

    When and where to look

    Typically during an overnight watch, the Perseids are capable of producing a number of bright, flaring and fragmenting meteors, which leave fine trains in their wake. On the night of shower maximum, the Perseid radiant is not far from the famous "Double Star Cluster" of Perseus. Low in the northeast during the early evening, it rises higher in the sky until morning twilight ends observing.

    Shower members appearing close to the radiant have foreshortened tracks; those appearing farther away are often brighter, have longer tracks, and move faster across the sky. About five to 10 of the meteors seen in any given hour will not fit this geometric pattern, and may be classified as sporadic or as members of some other (minor) shower.

    Perseid activity increases sharply in the hours after midnight, so plan your observing times accordingly. We are then looking more nearly face-on into the direction of the Earth’s motion as it orbits the Sun, and the radiant is also higher up. Making a meteor count is as simple as lying in a lawn chair or on the ground and marking on a clipboard whenever a "shooting star" is seen. Watching for the Perseids consists of lying back, gazing up into the stars, and waiting. It is customary to watch the point halfway between the radiant (which will be rising in the northeast sky) and the zenith, though its all right for your gaze to wander.

    Counts should be made on several nights before and after the predicted maximum, so the behavior of the shower away from its peak can be determined. Usually, good numbers of meteors should be seen on the preceding and following nights as well. The shower is generally at one-quarter strength one or two nights before and after maximum.

    A few Perseids can be seen as much as two weeks before and a week after the peak. The extreme limits, in fact, are said to extend from July 17 to Aug. 24, though an occasional one might be seen almost anytime during the month of August.

    Photographing meteors

    The Perseids are an excellent meteor display to attempt to photograph. Meteor photography is popular. However, the chance of your recording a meteor is enhanced by using a fast lens (f 2.8 or better) and ultrafast film (ISO 400 to 1600). It makes no difference whether the camera is clock-driven or fixed on a tripod.

    If your camera has an electronic shutter see if it also has a long time exposure mode that doesn't draw current. Otherwise, put in fresh batteries and plan on replacing them the next day. Mechanical shutters are preferable for long time exposures for this reason.

    If all you have is a digital camera, then give it a try. Otherwise, use a film-based camera instead. The reason for this is that digital cameras suffer from thermal noise during exposures of more than a second or so.

    In a dark sky, exposures of 10 to 20 minutes long can be made, but should be kept much shorter if background light threatens to fog the film. Slight moonlight, twilight or city glow can be tolerated, as they have little to do with the efficiency of a particular lens-film combination in recording bright meteors.

    A successful photograph has many added values if an observer has witnessed and described the same meteor. Also, the chance of obtaining a good meteor picture can be increased by pointing the camera well away from the radiant.

    No danger

    Many years ago, a phone call came into New York’s Hayden Planetarium. The caller sounded concerned after hearing a radio announcement of an upcoming Perseid display and wanted to know if it would be dangerous to stay outdoors on the night of the peak of the shower (perhaps assuming there was a danger of getting hit). These meteoroids, however, are no bigger than sand grains or pebbles, have the consistency of cigar ash and are consumed many miles above our heads.

    The caller was passed along to the Planetarium’s Chief Astronomer who commented that there are only two dangers from Perseid watching: getting drenched with dew and falling asleep!

    Whether you plan to take photographs, make detailed meteor counts or just lie back and watch nature put on a show, there should be plenty to see late on the nights of Aug. 11 and 12. As one long-time meteor enthusiast once noted: "Meteor observing is relaxing and enjoyable, potentially dramatic and just plain fun!"

    It only takes a spark to start a fire, be that spark.




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    Default Re: The Astronomy Thread

    Alas, it's been cloudy and rainy here the past couple of days. And the extended forecast is for continued sporadic rain. The worst drought here since 1988 would have to end just prior to the Perseid meteor shower.
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