# Where can I find a list of galactic Long/Lat for stars?

I can only seem to find right ascension and declination, which if I understand is position when looking upwards, where as galactic long/lat should be position if you imagine a sphere of the plane of the sky from "outside". Unless I'm misunderstanding.

I'd love a list of the galactic long/lat for stars if anyone knows where to get one?

• en.wikipedia.org/wiki/Galactic_coordinate_system has equations for converting between equatorial & galactic coordinates. Those equations can be derived using standard spherical trigonometry formulas. May 8 at 11:22
• Thanks, not too confident with using them, was just wondering if it existed as an explicit list anywhere as well May 8 at 16:02
• I'm not sure you are understanding. RA-dec is based on the equator and the direction of the first point of Aries, not on "Looking upwards", and galactic long/lat is based on the milky way and the direction of the centre of the galaxy. Both are imagined as a sphere around the Earth, looked at from the inside. May 8 at 16:16
• Ah right, may have misunderstood in that case. If you were projecting the stars onto a sphere, for example if you were making a spherical star map, would that make whatever you project onto the sphere the mirror of where it should be, if galactic long/lat are seen "from the inside" as it were? May 8 at 16:51
• astrophysicsandpython.com/2021/04/19/… complete with code examples May 8 at 17:30

The Yale bright star catalogue has glon and glat data right in the table

It looks like this:

bsn name hd ... glon glat vmag spectype
1 3 114.44 -16.88 6.7 A1Vn
2 6 98.33 -61.14 6.29 gG9
3 33 Psc 28 93.75 -65.93 4.61 K0IIIbCN-0.5
4 86 Peg 87 106.19 -47.98 5.51 G5III
5 123 117.03 -3.92 5.96 G5V
6 142 321.61 -66.38 5.7 G1IV
7 10 Cas 144 118.06 1.75 5.59 B9III
8 166 111.26 -32.83 6.13 K0V
9 203 52.21 -79.14 6.18 A7V

I've cut several other columns.

You can get the original file (in binary or ascii form) from http://tdc-www.harvard.edu/catalogs/bsc5.html

It has several thousand stars down to magnitude 7

• Awesome, thanks. Quick question, it seems for earth long we use 180 degrees east and west (+/-), if you get a galactic long (glon?) that is over 180 do you minus 180 from it and then make it negative to find the equivalent in a 180 east/west system? May 8 at 16:41
• I suppose you could do that, -1 degree is just another way of writing 359 degrees, if you are measuring angles in a circle May 8 at 16:46

I found an online program which calcauates galacitic logitude and latitude from equatorial coordinates of right ascension and declination.

https://ned.ipac.caltech.edu/coordinate_calculator?in_csys=Equatorial&in_equinox=J2000.0&obs_epoch=2000.0&ra=00%2042%2044.3&dec=41%2015%2009&pa=0.0&out_csys=Galactic&out_equinox=J2000.0

So if you need the galactic coordinates of stars not listed in a catag that gives galactic longitude and latitude you can convert their equitorial coordinates to galactic coordinates.

And, depending on how much you already know about galactic coordinates, you might want to see my post number 36 on page 2 of this thread: