Binary Catalogs

Binary catalogs use the internal representation of the computer on which they are used. They are currently expected to be in B1950 equatorial coordinates unless NMAG is negated, though skymap can be told to expect J2000 instead. All angular variables are in radians so they don't have to be converted to work in Fortran trigonometric functions. We provide the SAO Catalog, the PPM Catalog, and the IRAS Point Source Catalog in this format.

The catalog header tells the program what to expect in each The first 28 bytes of each file contains the following information:

Integer*4 STAR0	Subtract from star number to get sequence number
Integer*4 STAR1	First star number in file
Integer*4 STARN	Number of stars in file
		If negative, coordinates are J2000 instead of B1950
Integer*4 STNUM	0 if no star ID numbers are present
		1 if star ID numbers are in catalog file
		2 if star ID numbers are region nnnn (GSC)
		3 if star ID numbers are region nnnnn (Tycho)
		4 if star ID numbers are integer*4 not real*4
		<0 No ID number, but object name of -STNUM characters
		   at end of entry
Integer*4 MPROP	0 if no proper motion is included
		1 if proper motion is included
		2 if radial velocity is included
Integer*4 NMAG	Number of magnitudes present (0-10)
		If negative, coordinates are J2000 instead of B1950
Integer*4 NBENT	Number of bytes per star entry

Each entry in the catalog contains the following information:

Real*4 XNO		Catalog number of star [optional]
Real*8 SRA0		B1950 Right Ascension (radians)
Real*8 SDEC0		B1950 Declination (radians)
Character*2 ISP		Spectral type (2 characters)
Integer*2 MAG(NMAG)	V Magnitude * 100 [0-10 may be present]
Real*4 XRPM		R.A. proper motion (radians per year) [optional]
Real*4 XDPM		Dec. proper motion (radians per year) [optional]
Real*8 SVEL		Radial velocity in kilometers per second (optional)
Character*(-STNUM)	Object name [optional, precludes catalog number]

Catalog numbers may be omitted to save space if they are monotonically increasing integers. Proper motions may be omitted if they are not known. There may be up to 10 magnitudes.

Last updated 24 September 2012 by Jessica Mink, SAO Telescope Data Center