# Stars in constellation patterns by catalogue number?

I need a resource that can tell me the stars that make up a constellation (pattern), preferably by Henry Draper or some catalogue number? All i can find is lists of every star in a constellation (area) or incomplete lists of stars by name.

If this doesn't exist can you suggest a way to work it out myself?

• There is no standardised way of drawing the constellation figures. – James Screech May 29 '16 at 18:13
• Maybe, I can use the most brilliant stars. – VansFannel May 29 '16 at 20:49
• It's not always the brightest stars, though. I would recommend just going through Wikipedia, looking at the images they have, and matching the stars at the vertices in those images. It'll take a bit of time, but probably less time than it would take you to do it any other way. – J. O'Brien Antognini May 31 '16 at 16:25
• You must manually do this, Vans - - there's no "logical" way (such as brightest) to get them. (Note that even if it was "brightest", that wouldn't tell you how to connect them.) – Fattie Jul 8 '16 at 19:04
• In other prograns such as Google's, they have an overlay from some famous drawing of the constellations. – JDługosz Jul 8 '16 at 20:58

What you ask for does not exist. There is no standard for what the patterns are. In modern astronomy, the constellations are areas of the sky. You can find lists of the stars in each area, but it seems that you want only the stars in the "pattern".

When you see a star map, lines are sometimes drawn between the brighter stars. These help people to compare the stars to the map, our brains like to look for connections, and so linking the stars together helps us to make sense of the sky. However different stellar-cartographers will draw the lines in different ways. Consider Gemini:

The same constellation is represented in different ways. Neither presentation is official, it is an artistic choice which stars to include and how to link them. It is therefore impossible to say which stars "make up a pattern" and which do not.

However, if you look at the catalogues, and see which stars have received a Bayer designation you will have a list of the visible stars in each constellation. This won't, of course, tell you how the stars may be linked.

If you visit https://github.com/Stellarium/stellarium/tree/master/skycultures you see several sky cultures that include various constellation shapes (you also get this directory when you download stellarium).

As an example, lets look at https://github.com/Stellarium/stellarium/tree/master/skycultures/western_rey, in particular the file https://github.com/Stellarium/stellarium/blob/master/skycultures/western_rey/constellationship.fab and line number 127 which reads:

Aql 10 98036 97649 97649 97278 97278 96229 96229 95501 95501 97804 99473 97804 95501 93747 93747 93244 95501 93805 93805 93429

The "Aql" stands for the for the constellation Aquila, the Eagle (https://github.com/Stellarium/stellarium/blob/master/skycultures/western_rey/constellation_names.eng.fab verifies this)

The "10" means there are 10 lines that make up the markings for Aquila. Note that these lines are specific to the H.A. Rey skyculture. Different cultures will have different lines.

The next 20 number represent the lines themselves. For example "98036 97649" is a line from star 98036 to star 97649, and "97649 97278" is a line from star 97649 to star 97278. Since these two lines share star 97649, they are connected, but that's not always the case with adjacent lines. For example "95501 97804 99473 97804" represents a line from star 95501 to star 97804 and another unconnected line from star 99473 to star 97804.

The next question: what exactly IS star 98036?

If you look at https://github.com/Stellarium/stellarium/blob/master/stars/default/name.fab you'll see it's Beta Aquilae, but not all stars have names in this file, and the name isn't particularly helpful in finding the star itself.

Stellarium itself stores this data in the "catalog files" at https://github.com/Stellarium/stellarium/tree/master/stars/default with the format described at http://stellarium.sourceforge.net/wiki/index.php/Star_Catalogue_Format

However, this can be ugly. Since Stellarium uses the standard Hipparcos catalog, you can visit ftp://cdsarc.u-strasbg.fr/pub/cats/I/239/ and download "hip_main.dat.gz". The format is described at http://cdsarc.u-strasbg.fr/viz-bin/Cat?I/239

The line relating to star 98036 starts:

H| 98036| |19 55 18.77|+06 24 28.6| 3.71|...

which tells us star 98036 is at J2000 right ascension 19h55m18.77s, declination +06 degrees, 24'28.6" declination, and has a magnitude of 3.71. This agrees almost perfectly with https://en.wikipedia.org/wiki/Beta_Aquilae (the declination is slightly off, but this may be because Beta Aquilae is a double star, and Hipparcos references the brighter star and Wikipedia references the midpoint of the double star-- or something).

There are other files in the stellarium github (eg, culture-specific star names) that also use the Hipparcos numbering designation.

I did this manually some years ago by listing the BSC numbers of stars and drawing lines between them. The resulting data file can be found at the bottom of this page: BSC constellation lines. As @james-screech mentioned, there is no standard way to draw the constellations, so this is just one (my) interpretation. To give you some idea, maps (in Dutch) using these data can be found here: NP, Eq 0h, Eq 12h, SP.

You can find the constellations here:

http://www.iau.org/public/themes/constellations/

Take a look at the gif for each constellation and you will find out which stars are connected (there is also a text file for the boundaries of each constellation in RA and Dec, though this is not what you want).

I have compiled exactly the kind of list that you're looking for.

The stars are identified by their Yale Bright Star Catalogue HR designation. This is the best catalogue to use to define the IAU constellations because it is conveniently-sized (only 9,110 stars, down to a magnitude of about 7.5) and all the IAU constellation patterns can be defined in terms of these stars.

It is based on canonical IAU constellations. I also throw in J2000 positions, magnitudes and names for each of the stars in each pair of the constellation.

For example, Cassiopeia appears as 4 lines (below shown wrapped)

Cas 21  2.294583    59.149722   2.27    Caph|bet Cas|11 Cas
168 10.127083   56.537222   2.23    Schedar|alf Cas|18 Cas
Cas 168 10.127083   56.537222   2.23    Schedar|alf Cas|18 Cas
264 14.177083   60.716667   2.47    BU 499A|BU 1028|gam Cas|27 Cas
Cas 264 14.177083   60.716667   2.47    BU 499A|BU 1028|gam Cas|27 Cas
403 21.454167   60.235278   2.68    Ruchbah|BUP 19A|del Cas|37 Cas
Cas 403 21.454167   60.235278   2.68    Ruchbah|BUP 19A|del Cas|37 Cas
542 28.598750   63.670000   3.38    Segin|eps Cas|45 Cas


Note that the asterisms defined by the IAU may be slightly different from what you see in planetarium programs or star charts. However, the IAU should be seen as an authoritative source and any variation on the patterns is up to the "poetic license" of the user.

Most of these stars (possibly all, I haven't actually checked) will have a Hipparcos (HIP) and/or Tycho (TYC) index entry as well and also