# Equatorial Coordinate System

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#### votefornimitz

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I am a wiz at the Altitude-Azimuth system of celestial navigation, going so far to build my own sextant*** for that purpose...<br /><br />I recently purchased a book on Messier Objects to aid in my Messier hunting, but am having difficulty adjusting to the Equatorial coordinate system which is used in the book (granted it would have been impossible for them to use Altazimuth), and reading up on it doesn't seem to be aiding much in understanding it...<br /><br />So I was wondering if any of you had a way of understanding it that would make it easier for me to know what I was doing.. <br /><br />****For some reason I keep calling those astrolabes...<br /><br /> <div class="Discussion_UserSignature"> <span style="color:#993366">In the event of a full scale nuclear war or NEO impact event, there are two categories of underground shelters available to the public, distinguished by depth underground: bunkers and graves...</span> </div>

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#### MeteorWayne

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That's difficult to envision without some tools.<br /><br />The way it works in that it is based on the plane of the solar system ( the ecliptic).<br /><br />The ecliptic, will therefore form a line through where the sun (specifically) and all the planets (generally) orbit.<br />The moon is inclined a bit more than that, but generally is in the same neighborhood.<br /><br />So all the signs of the Zodiac....Gemini, Pisces, Taurus, Aries, etc trace that path across the sky.<br /><br />Above and below are the zenith and nadir of that reference. Since it's 90 dgrees from the plane to overhead, what's called Declination is measured in +/- 90 gegrees.<br /><br />For the other plane, along the ecliptic, the 360 degrees is divided into 24 Hours, made of 60 minutes. That's 15 degrees per hour. 15X24=360 degrees.<br /><br />The zero hour reference is where the sun is on the Vernal (spring) equinox.<br /><br />So, traveling from that point eastward, every 15 degrees is one hour of "Right Ascention"<br /><br />I'm not sure that would make sense to me, but it's right.<br /><br />A better way to grasp the concept would be a 3D image showing it from outside.<br /><br />I'll look for one, hopefully someone else will beat me to it. <br /><br /><font color="yellow">EDIT:: IGNORE THIS POST, BAD INFO ON MY PART. MW</font>/safety_wrapper> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

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#### votefornimitz

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The picture would help, I'll google and see what I get...<br /><br />And I read what you just told me on wikipedia and what not, but comparing that to the equatorial star charts I have just gives me more confusion...<br /><br />Thank you for the advice though...<br />I'll get it eventually...<br />Hopefully....<br /> <div class="Discussion_UserSignature"> <span style="color:#993366">In the event of a full scale nuclear war or NEO impact event, there are two categories of underground shelters available to the public, distinguished by depth underground: bunkers and graves...</span> </div>

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#### votefornimitz

##### Guest
<url target="_blank" href="http://www.linux-user.de/ausgabe/2006/02/068-stellarium/abbildung5.png">>http://www.linux-user.de/ausgabe/2006/02/068-stellarium/abbildung5.png&gt; Is this it? </url><br /><br />If so it makes a bit more sense, but it seems to be quite convoluted.... <br /><br />Stupid HTML system... <div class="Discussion_UserSignature"> <span style="color:#993366">In the event of a full scale nuclear war or NEO impact event, there are two categories of underground shelters available to the public, distinguished by depth underground: bunkers and graves...</span> </div>

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#### MeteorWayne

##### Guest
Maybe tell us what the star charts are telling you, then we can help? <br /><br /> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

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#### votefornimitz

##### Guest
Sorry about the link earlier...<br /><br />Ok, I'm looking at a a star chart, it has Declination along the Y axis and Right Ascension on the X axis...<br /><br />Polaris isn't even on the chart, with most of the bowl portion of Ursa Minor being on the very top of the graph Between 70-80+ Declination and between the 17th-15th hour....<br /><br />The Orion region of the chart (The area I am most familiar with) Shows Rigel as being 5.5th Right Ascension and -8 Declination, while showing Sirius at 7th Right Ascension and 18 Declination, sort of a diagonal with Rigel on the chart, yet personal observation would tell me that Sirius should be almost directly underneath Rigel, having nearly the same azimuth....<br /><br />Hence my confusion....<br /><br />That an on this chart the milky way starts out at the top of the graph on the Left side, goes down to the very bottom in the middle, and then goes back to its original height at the right....<br /><br />Kind of a "WTH" if you as me lol.... <div class="Discussion_UserSignature"> <span style="color:#993366">In the event of a full scale nuclear war or NEO impact event, there are two categories of underground shelters available to the public, distinguished by depth underground: bunkers and graves...</span> </div>

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#### MeteorWayne

##### Guest
OK, first of all, my earlier post was incorrect. I left it there but edited in a warning.<br /><br />Here's the deal.<br /><br />It's called an eqatorial system for a reason I should have realized; it's based on the equator!!<br /><br />Zero degrees Declination (the one on the chart up and down, in degrees) is directly over the equator.<br />The earth's axis of rotation is at +90 (the north pole) and -90 degrees (the south pole).<br />Each degree is divided into 60 minutes; each of those is divided into 60 seconds. This means the sky from north pole to south pole is divided into 648,000 (180x60x60) parts using degrees, minutes, and seconds.<br />Polaris (the north star) is actually at +89 degrees, 18 minutes, 38.8 seconds (currently; that changes over tens of thousands of years).<br /><br />Now the horizontal scale (along the equator) is 360 degrees around.<br />It is divided into what are called hours of Right Ascension (R.A.).<br /><br />The 360 degrees is divided into 24 hours of 15 degrees each, each hour is divided into 60 minutes, each of those into 60 seconds. 0 hours is in Pisces, 1 hour is 15 degrees further east. This divies the horizontal direction into 86,400 pieces using hours, minutes and seconds (24x60x60)<br /><br />The only place this system seems to make perfect sense is at the equator. But if you based a coordinate system on say your location, it would only work there, mine would be different. For example, I'm at ~ 41 degrees north, that means for me Polaris is always at 49 degrees elevation.<br /><br />This system is designed to create a standard grid based on the most common thing, the earth's axis of rotation.<br /><br />Hope this helps. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

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#### votefornimitz

##### Guest
I get it now...<br /><br />After reading that, and then comparing my equatorial charts to my altazimuth charts I think I understand it perfectly....<br /><br />Or well enough I can find things I am looking for...<br /><br />Thank you very much!<br />Now the only thing preventing me from finding the Messiers is light pollution...<br /><br />Got any solutions for that <img src="/images/icons/laugh.gif" />? <div class="Discussion_UserSignature"> <span style="color:#993366">In the event of a full scale nuclear war or NEO impact event, there are two categories of underground shelters available to the public, distinguished by depth underground: bunkers and graves...</span> </div>

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#### MeteorWayne

##### Guest
A Red Rider 200 Shot Air Rifle with a Compass in the Stock <img src="/images/icons/smile.gif" /> <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

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#### votefornimitz

##### Guest
The neighbors would respond with Air Rifles, I'm afraid though....<br /><br />An emp burst would be nice... <div class="Discussion_UserSignature"> <span style="color:#993366">In the event of a full scale nuclear war or NEO impact event, there are two categories of underground shelters available to the public, distinguished by depth underground: bunkers and graves...</span> </div>

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#### garfieldthecat

##### Guest
"Thank you very much! <br />Now the only thing preventing me from finding the Messiers is light pollution... <br /><br />Got any solutions for that ? "<br /><br />Well there are some filters that are supposed to diminish the light pollution... but they're expensive compared to their final small effect: for nebulaes and galaxies they pretty much worth nothing, a little better on star clusters<br /><br />Best way is to take a weekend from time to time and go to the countryside with your material: camping is a nice and pleasant way, or if you got familly living in a rural area you can invite yourself every clear saturday night <img src="/images/icons/smile.gif" />

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