# Has somebody figured out how to equate cities with stars? **URL:** \ **Category:** Factual Questions\ **Created:** [March 26, 2009, 5:35pm UTC](https://boards.straightdope.com/t/has-somebody-figured-out-how-to-equate-cities-with-stars/490887 "2009-03-26T17:35:50Z")\ **Posts on this page:** 15\ **Page:** 1
**Author:** ![Zeldar](https://avatars.discourse-cdn.com/v4/letter/z/b77776/32.png) [@Zeldar](https://boards.straightdope.com/u/Zeldar)\ **Post date:** [March 26, 2009, 5:35pm UTC](https://boards.straightdope.com/t/has-somebody-figured-out-how-to-equate-cities-with-stars/490887/1 "2009-03-26T17:35:50Z")
I wasn’t sure which forum this should go in. It is a question with a yes/no answer, I feel sure. But it may bring on as much discussion as answers, per se. Using [this page](http://cse.ssl.berkeley.edu/SEGwayed/lessons/findplanets/find_comet/coordinates.html) for a review of the terminology (if needed) has some website or product manufacturer taken on the task of using latitude/longitude coordinates on Earth as a parallel to right ascension/declination on the celestial sphere to equate the various cities (and other geographical features on the planet) with points in the sky? For example, which star corresponds with Nashville? New York City? Paris? I’ll keep Googling to try to find an online answer, but I thought the idea might appeal to some Dopers as well. A link to such a site will serve to answer the question in the title. ---
**Author:** ![OldGuy](https://avatars.discourse-cdn.com/v4/letter/o/3bc359/32.png) [@OldGuy](https://boards.straightdope.com/u/OldGuy)\ **Post date:** [March 26, 2009, 5:49pm UTC](https://boards.straightdope.com/t/has-somebody-figured-out-how-to-equate-cities-with-stars/490887/2 "2009-03-26T17:49:31Z")
> [@Zeldar](#): > > has some website or product manufacturer taken on the task of using latitude/longitude coordinates on Earth as a parallel to right ascension/declination on the celestial sphere to equate the various cities (and other geographical features on the planet) with points in the sky? There is no unique way to do this. Declination can be translated to latitude directly, it is not obvious how right ascension translates to longitude. It’s obvious that with 24 hours around the circle, each hour corresponds to 15 degrees so each minute and second of RA corresponds to 15 minutes or seconds of RA, but since the earth rotates under the stars, there is no fixed way to match up the starting points of the scale. I guess you could arbitrarily assign 0 RA to 0 longitude. ---
**Author:** ![Zeldar](https://avatars.discourse-cdn.com/v4/letter/z/b77776/32.png) [@Zeldar](https://boards.straightdope.com/u/Zeldar)\ **Post date:** [March 26, 2009, 5:58pm UTC](https://boards.straightdope.com/t/has-somebody-figured-out-how-to-equate-cities-with-stars/490887/3 "2009-03-26T17:58:48Z")
> [@OldGuy](#): > > There is no unique way to do this. Declination can be translated to latitude directly, it is not obvious how right ascension translates to longitude. It’s obvious that with 24 hours around the circle, each hour corresponds to 15 degrees so each minute and second of RA corresponds to 15 minutes or seconds of RA, but since the earth rotates under the stars, there is no fixed way to match up the starting points of the scale. I guess you could arbitrarily assign 0 RA to 0 longitude. I would just assume (why not?) that 0 RA would be Greenwich meridian. The Vernal Equinox (0 RA) is a fixed point on the sky. [This page](http://www.krysstal.com/coordsystems.html) gives more details on that issue. What I’m hoping to find is a reference that correlates a good number of places on earth with places in the sky. Doing the lookup or calculations would take some time that I hope somebody else has already done. ---
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [March 26, 2009, 6:02pm UTC](https://boards.straightdope.com/t/has-somebody-figured-out-how-to-equate-cities-with-stars/490887/4 "2009-03-26T18:02:43Z")
No, no one has done this. Why would they? (I say this without having done any searching what so ever.) ---
**Author:** ![chrisk](https://avatars.discourse-cdn.com/v4/letter/c/6de8d8/32.png) [@chrisk](https://boards.straightdope.com/u/chrisk)\ **Post date:** [March 26, 2009, 6:10pm UTC](https://boards.straightdope.com/t/has-somebody-figured-out-how-to-equate-cities-with-stars/490887/5 "2009-03-26T18:10:51Z")
Most of the best stars would be over the ocean. 😉 ---
**Author:** ![Zeldar](https://avatars.discourse-cdn.com/v4/letter/z/b77776/32.png) [@Zeldar](https://boards.straightdope.com/u/Zeldar)\ **Post date:** [March 26, 2009, 6:13pm UTC](https://boards.straightdope.com/t/has-somebody-figured-out-how-to-equate-cities-with-stars/490887/6 "2009-03-26T18:13:53Z")
> [@naita](#): > > No, no one has done this. Why would they? (I say this without having done any searching what so ever.) For the hell of it? For kicks? For something to do? ---
**Author:** ![Zeldar](https://avatars.discourse-cdn.com/v4/letter/z/b77776/32.png) [@Zeldar](https://boards.straightdope.com/u/Zeldar)\ **Post date:** [March 26, 2009, 6:15pm UTC](https://boards.straightdope.com/t/has-somebody-figured-out-how-to-equate-cities-with-stars/490887/7 "2009-03-26T18:15:03Z")
> [@chrisk](#): > > Most of the best stars would be over the ocean. 😉 Probably true. And many cities would be some tiny speck that would need a telescope to see. But still… ---
**Author:** ![Fubaya](https://avatars.discourse-cdn.com/v4/letter/f/c2a13f/32.png) [@Fubaya](https://boards.straightdope.com/u/Fubaya)\ **Post date:** [March 26, 2009, 11:30pm UTC](https://boards.straightdope.com/t/has-somebody-figured-out-how-to-equate-cities-with-stars/490887/8 "2009-03-26T23:30:17Z")
Since the earth orbits and wobbles, the stars move around in the sky and the map would need to be adjusted a lot. Having said that, everyone knows the country stars correspond with Nashville. ---
**Author:** ![Zeldar](https://avatars.discourse-cdn.com/v4/letter/z/b77776/32.png) [@Zeldar](https://boards.straightdope.com/u/Zeldar)\ **Post date:** [March 27, 2009, 11:29am UTC](https://boards.straightdope.com/t/has-somebody-figured-out-how-to-equate-cities-with-stars/490887/9 "2009-03-27T11:29:58Z")
> [@Fubaya](#): > > Since the earth orbits and wobbles, the stars move around in the sky and the map would need to be adjusted a lot. What you say has been taken into account and adjusted for in such tables as [this one](http://www.cosmobrain.com/cosmobrain/res/brightstar.html), where you’ll note (out to the right) the RA J2000 and DEC J2000 headings. These qualifications take into account that movement you mention and have set, as a reference point, where the Vernal Equinox (where the Ecliptic and Celestial Equator met) _was_ in 2000. For more on the j2000 designation, [look here.](http://code.google.com/p/date2et/) Since the coordinates are good enough for charts like that one linked to above, all I’m asking is whether anybody has taken the time to convert the celestial coordinates to a system that parallels the Latitude and Longitude coordinates we use for GPS type designations of places on Earth and thus set up a one-to-one charting of where stars would be _if_ they were places on Earth. It’s mostly a matter of converting points on one coordinate system to points on another and building up matches between data points. If you prefer to go in the other direction, think of where in the sky New York City would be if its Latitude and Longitude (40[sup]o[/sup] 42’ 51" and 74[sup]o[/sup] 0’ 23" – according to World Almanac 2001) were converted to their corresponding Declination and Right Ascension. Since I have thought it amusing enough to ask the question, I can’t imagine that _nobody_ has taken the trouble to carry out the task of doing it. Not that I really want to do it myself: I just want to see what such a chart would look like. And since websites specialize in stuff much weirder than this (to my way of thinking) I thought I’d at least ask Dopers if they’ve run across such a thing. ---
**Author:** ![DJBFivE](https://avatars.discourse-cdn.com/v4/letter/d/e99b99/32.png) [@DJBFivE](https://boards.straightdope.com/u/DJBFivE)\ **Post date:** [March 27, 2009, 3:11pm UTC](https://boards.straightdope.com/t/has-somebody-figured-out-how-to-equate-cities-with-stars/490887/10 "2009-03-27T15:11:11Z")
It IS entirely possible that you are the first person to ever consider this ---
**Author:** ![Zeldar](https://avatars.discourse-cdn.com/v4/letter/z/b77776/32.png) [@Zeldar](https://boards.straightdope.com/u/Zeldar)\ **Post date:** [March 27, 2009, 6:45pm UTC](https://boards.straightdope.com/t/has-somebody-figured-out-how-to-equate-cities-with-stars/490887/11 "2009-03-27T18:45:49Z")
> [@DJBFivE](#): > > It IS entirely possible that you are the first person to ever consider this Now _that_ would be weird! ---
**Author:** ![anson2995](https://avatars.discourse-cdn.com/v4/letter/a/c77e96/32.png) [@anson2995](https://boards.straightdope.com/u/anson2995)\ **Post date:** [March 27, 2009, 7:23pm UTC](https://boards.straightdope.com/t/has-somebody-figured-out-how-to-equate-cities-with-stars/490887/12 "2009-03-27T19:23:05Z")
Mapping stars to cities may be a unique idea, but the idea of mapping the night sky to a sphere is not. Celestial globes used to be crucial to navigation. Here are links to pictures of a couple of [very old](http://www.murrayhudson.com/antique_globes/10209g3.jpg) [examples](http://www.nmm.ac.uk/blogs/collections/D7855_1.JPG), and a few [modern](http://www.geodus.com/en/world-globe-columbus-sternehimmel_813446.htm) [examples](http://www.amep.com/standarddetail.asp?cid=298). ---
**Author:** ![Zeldar](https://avatars.discourse-cdn.com/v4/letter/z/b77776/32.png) [@Zeldar](https://boards.straightdope.com/u/Zeldar)\ **Post date:** [March 27, 2009, 7:27pm UTC](https://boards.straightdope.com/t/has-somebody-figured-out-how-to-equate-cities-with-stars/490887/13 "2009-03-27T19:27:41Z")
> [@anson2995](#): > > Mapping stars to cities may be a unique idea, but the idea of mapping the night sky to a sphere is not. Celestial globes used to be crucial to navigation. Here are links to pictures of a couple of [very old](http://www.murrayhudson.com/antique_globes/10209g3.jpg) [examples](http://www.nmm.ac.uk/blogs/collections/D7855_1.JPG), and a few [modern](http://www.geodus.com/en/world-globe-columbus-sternehimmel_813446.htm) [examples](http://www.amep.com/standarddetail.asp?cid=298). Glad you made that point, **anson2995** , because I was beginning to feel as if I were the only person to know about such a thing. Where are all the astronomy Dopers? I’d have thought at least one would have checked out the thread title. ---
**Author:** ![Freddy\_the\_Pig](https://avatars.discourse-cdn.com/v4/letter/f/a587f6/32.png) [@Freddy\_the\_Pig](https://boards.straightdope.com/u/Freddy_the_Pig)\ **Post date:** [March 27, 2009, 9:16pm UTC](https://boards.straightdope.com/t/has-somebody-figured-out-how-to-equate-cities-with-stars/490887/14 "2009-03-27T21:16:32Z")
At the moment each day when the vernal equinox passes over the Prime Meridian, the earth and sky coordinates are in alignment, and each star will be at the zenith over its matched city. However that moment can occur at any time of the day or night, and cycles around the clock in the course of a year. When it occurs during the daytime, of course, the star isn’t visible at the zenith. So I have to say, I don’t see anything all that special about this alignment. But far be it from me to discourage anyone else. If it floats your boat, go for it. I hope Chicago matches to something cool, like Delta Cephei or something. ---
**Author:** ![Alive\_At\_Both\_Ends](https://avatars.discourse-cdn.com/v4/letter/a/73ab20/32.png) [@Alive\_At\_Both\_Ends](https://boards.straightdope.com/u/Alive_At_Both_Ends)\ **Post date:** [March 27, 2009, 10:13pm UTC](https://boards.straightdope.com/t/has-somebody-figured-out-how-to-equate-cities-with-stars/490887/15 "2009-03-27T22:13:18Z")
> [@Zeldar](#): > > I would just assume (why not?) that 0 RA would be Greenwich meridian. You still have to decide whether increasing RA equates to travelling east or west. Either way, and just to start the ball rolling, London (and most of England) comes out somewhere in Cassiopeia I think.