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Thread: Astronomy Basics - How do I figure out star distances

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    Astronomy Basics - How do I figure out star distances

    Here's a fun puzzle I'm having to deal with as I make a realistic star travel campaign setting. I've managed to find a list of all the yellow-orange stars within 100 light years of earth, and most of them up to about 50 light years have enough data on them that you can tell if they might possibly have a rocky planet in the water zone that would generate life. The rest, Im just guessing based on feel. I know the distance each is from earth and what constellation they are in or near, but I don't know how to figure how far they are from each other. There is a planetarium with an observatory in my home city, I was wondering about asking them, but there are lots and lots of potentially habitable planets. Hmmmm. Anyone have any resources on this, where I can determine one star's distance from another if I have the names of the stars?
    Last edited by Engineer Doramos; 10-20-2008 at 02:41 PM.

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    [comment about D&D 4E]I have to ask myself, am I just buying a name here? If I fell in love with a gal named Wanda ten years ago, does that mean that every new Wanda that comes along is going to be just as groovy?
    I like the old Wanda, This new Wanda looks like high maintenence.
    ~nordo billingswary at the K&Co forums

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    Quote Originally Posted by Greylond View Post
    Cool, thanks Greylond! Ugh, thats a lot of math I have to do. Not even sure if my mac can look up sines and cosines, and I haven't had a scientific calculator in a long time.


    At least I don't have to use the equations at the bottom of the linked math page. ><


    I'm also not sure where in all the data I have the RA and DEC are, but I might find it there... if not I search elsewhere.


    I already have 72 planets and I'm somewhere between 70 and 80 light years out. You can see there's a massive amount of work I have to do.

    [Edit] After pondering the sheer logistics of trying to keep track of all the distances between hundreds of planets, I'm going to have to try another tactic. I still need to find out their general locations to one another however, especially to figure out history bits.
    Last edited by Engineer Doramos; 10-21-2008 at 01:08 AM.

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    Distance between stars? Find the x, y and z axes.

    Distance^2 = (x1 - x2)^2 + (y1 - y2)^2 + (z1 - z2)^2

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    The problem is more like tying to group stars into sectors. If I have to work on a math equation on how far each star is from one another using Earth as an extrapolation every time, even if manage to get all the angles, it will be too clunky. If I try and predetermine all that data for the setting, I will go bonkers and lose my head of hair from pulling it all out. I figure since I have the constellations and the distance, I can eyeball it into some kind of 3-D sectors. There is also a page for each of the more known stars which tells me what stars are nearby, so that will help form sectors. I will still need to know the distance from one sector to nearby sectors though. Guess I need to look up a map of the constellations.

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    Quote Originally Posted by Lev Lafayette View Post
    Distance between stars? Find the x, y and z axes.

    Distance^2 = (x1 - x2)^2 + (y1 - y2)^2 + (z1 - z2)^2
    I'm with Lev Lafayette on this one. It's not going to be realistic, but figuring out the x, y and z coordinates based on Earth being at 0,0,0, you can then use the above formula to get distance from any two stars. For a game, that's more than accurate enough for me.
    Skunk
    a.k.a. Johnprime



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    If you can find it the old rpg Traveller 2300 had a map just like this.
    [comment about D&D 4E]I have to ask myself, am I just buying a name here? If I fell in love with a gal named Wanda ten years ago, does that mean that every new Wanda that comes along is going to be just as groovy?
    I like the old Wanda, This new Wanda looks like high maintenence.
    ~nordo billingswary at the K&Co forums

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    short of looking it up in a resource of some kind... it's a matter of plotting on a 3 dimensional grid where each planet is in relation to each other and then doing some fancy footwork with the pythagorean theorem. and that's assuming a still snapshot not taking into account movement within the galactic arm. ^^
    nijineko the gm: AG16, CoS. nijineko the player: AtG, RttToH; . The Journal of Tala'elowar Kiyiik! .
    CrystalBallLite: the best dice roller on the planet! . nijineko the archivist: the 3.x archive

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    The old X^2 + Y^2 + Z^2 formula is always the way to go. The sines and cosines you mentioned before are nessasary to set the three co-ordinates to begin with. Once you have those coordinates set (in stone, so to speak) then your game is ready to go. I have seen grid maps of 3D games before, and enjoyed some, and the designer always goes thru the trouble and work setting up these X,Y,Z things before hand. The formula is only for determining the straght line distance a ship must travel.

    BTW, I have done it myself in years gone by, and getting those coordinates set is A LOT OF WORK. So, don't envy my failer to finish the project. Getting the real time positions of the stars is a bunch more than I ever did. More power to you.
    Sure, Life IS like a bowl of cherries, but how SWEET they are depends on how much crap your willing to take to fertalize your DREAMS. Michael L. Cross

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    I'm still thinking eyeballing it works best for now, as I have a lot of other things to cover. However, I am really grateful for the help and pep talks. I think the two big deciding factors are 1) I dont have the energy to do all that math and 2) I don't have all the data needed for the RA and DEC of every star so I would have to search more, and some of these stars are quite obscure. I guess what I was really looking for was a genie to tell me of some website that is like babel fish with interstellar distances lol.

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    now you know why the sgf-1 stargate has a dial-a-planet approach! ^^ try explaining all that math on tv. =D

    as far as a list goes, try this link with a handy map. http://en.wikipedia.org/wiki/List_of_nearest_stars

    pretty useful. in my opinion, your best bet is to simply plot them yourself on a x-y-z grid, using whatever arbitrary units you feel like. that way you can set the centerpoint of 0,0,0 to whatever star you want, or even no star at all. then simply state how many units each star is away from that center point. then if you really want to, you can use the formulas given above to calculate exact distances between each other.

    even simpler than that, just eyeball it and blame any variance on the vageries of your medium of travel. in this case, close enough is good enough. (just don't let the astrogators know that!) ^^
    nijineko the gm: AG16, CoS. nijineko the player: AtG, RttToH; . The Journal of Tala'elowar Kiyiik! .
    CrystalBallLite: the best dice roller on the planet! . nijineko the archivist: the 3.x archive

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    I found a copy of the Traveler 2300 list and sent it to him. Hope it helps out...
    [comment about D&D 4E]I have to ask myself, am I just buying a name here? If I fell in love with a gal named Wanda ten years ago, does that mean that every new Wanda that comes along is going to be just as groovy?
    I like the old Wanda, This new Wanda looks like high maintenence.
    ~nordo billingswary at the K&Co forums

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    Holy Death Rays! That Traveller thing was way more useful than I was expecting! Thanks a million Greylond. It was a games workshop chart compiled from an actual star catalog, complete with x y and z vectors based in light years. Now I just have to find my chosen planets. Stupid mac can't even do square roots heh, maybe I need a widget for that. Let's see, according to google calculator, I got 16.1 light years to Eta Cassiopiae with them, and my reference says its 19.4. Could be drift, since theirs is based off 1969 data, and mine is probably more recent information. I'll monkey with the positions a bit to reflect that its 2150 ad. Thanks for the encouragement everyone! And yeah, Ninjineko, I was thinking a lot about the whole stargate thing a lot because I'm a fan of Fading Suns, which uses jumpgates left behind by elder aliens. I just wanted a free-cruising space system, where you could go anywhere. Eventually I found I had to place limits on it in order to make it playable, but I'm really happy with this new data! It will help make it so much easier to allow more player freedom (if they ever can afford a ship).

    [Edit] Ohh! I just thought - While I will have relay space stations on non life supporting star systems and in deep space, I now need a random encounter table for people who hyperjump to unknown regions of space. *Laughs evilly*
    Last edited by Engineer Doramos; 10-22-2008 at 06:21 AM.

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    Quote Originally Posted by Engineer Doramos View Post
    Holy Death Rays! That Traveller thing was way more useful than I was expecting! Thanks a million Greylond. It was a games workshop chart compiled from an actual star catalog, complete with x y and z vectors based in light years. Now I just have to find my chosen planets. Stupid mac can't even do square roots heh, maybe I need a widget for that. Let's see, according to google calculator, I got 16.1 light years to Eta Cassiopiae with them, and my reference says its 19.4. Could be drift, since theirs is based off 1969 data, and mine is probably more recent information. I'll monkey with the positions a bit to reflect that its 2150 ad. Thanks for the encouragement everyone! And yeah, Ninjineko, I was thinking a lot about the whole stargate thing a lot because I'm a fan of Fading Suns, which uses jumpgates left behind by elder aliens. I just wanted a free-cruising space system, where you could go anywhere. Eventually I found I had to place limits on it in order to make it playable, but I'm really happy with this new data! It will help make it so much easier to allow more player freedom (if they ever can afford a ship).

    [Edit] Ohh! I just thought - While I will have relay space stations on non life supporting star systems and in deep space, I now need a random encounter table for people who hyperjump to unknown regions of space. *Laughs evilly*
    I used that chart to find the coordinates of the nearest stars within a 21 light year radius! Course, I didn't bother to worry about drift as the data was fine for me.

    About 18 years ago, I had a Mac program that let you use an Excel spreadsheet to give it a coordinate system and it would display a pseudo 3d map of those coordinates on the screen. Can't remember the name but I'm sure that there's got to be programs that will do the same.

    Somewhere I have a link for a newer program that does star mapping, but I couldn't find it so I'll have to keep looking and post it if I do find it.
    Skunk
    a.k.a. Johnprime



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    Quote Originally Posted by Engineer Doramos View Post
    Stupid mac can't even do square roots heh, maybe I need a widget for that.
    there are any number of free scientific calculators for download. try apple downloads first, then google it if you still aren't happy.

    Quote Originally Posted by Skunkape View Post
    I used that chart to find the coordinates of the nearest stars within a 21 light year radius! Course, I didn't bother to worry about drift as the data was fine for me.
    copy for me too, please?
    nijineko the gm: AG16, CoS. nijineko the player: AtG, RttToH; . The Journal of Tala'elowar Kiyiik! .
    CrystalBallLite: the best dice roller on the planet! . nijineko the archivist: the 3.x archive

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