Celestia Forums

I am interested in doing these two things with Celestia 1.6.1 on Windows 7:

1) Edit the current constellation boundaries
2) Create new constellations (i.e. define a region of space as belonging to the new constellation)

I think I want to edit the boundaries.dat file, but I can't quite figure out the syntax. My best guess is that the file is defining a series of line segments by RA and Dec, and then assigning each segment to a constellation. Given any line segment will border two constellations, how are these segments assigned to one constellation and not the other? Does anyone here have a rough guide to the syntax, etc. of editing boundaries.dat?

Thanks,

Tim

Although this is not a formal description regarding the Celestia implementation of constellation boundaries, this answer may probably help you further.

I used the formal IAU site to figure this out:
http://www.iau.org/public/constellations/
The IAU page contains a description of their format:
For each constellation, there is a TXT file, describing the boundaries.
The text file contains a set of coordinates that defines the boundaries of the constellations in the sky.
The format is: HH MM SS.SSSS| DD.DDDDDDD|XXX
Where:
HH MM SS.SSSS defines the right ascension hour, minute and second with J2000 coordinates
DD.DDDDDDD defines the declination with J2000 coordinates
XXX is the abbreviation of the constellation name
| is the separator of the fields
Example:
22 57 51.6729| 35.1682358|AND


Celestia however, does not use the HH MM SS.SSSS notation for right ascension, but the minutes and seconds are defined in decimal values.
In Celestia the declination is the same format, using a + or - sign
In celestia the abreviation of the corresponding constellation is the same (I did not check all, but I think so)
Celestia uses a space separator instead of the | character
And finally in Celestia each row contains a "O" or "I" character.
As far as I can figure out, the "O" defines the start of a line and the "I" defines subsequent points on that line.
Each time a new "O" is given, you can see a direction change in the Constellation boundary.

Using the images on the IAU site, you can check it further out yourself.

Kind regards, Marco