The first 28 bytes of both PPM and PPMra contain the
following information:
Integer*4 STAR0=0 Subtract from star number to get sequence number
Integer*4 STAR1=1 First star number in file
Integer*4 STARN=378910 Number of stars in file
Integer*4 STNUM=1 0 if no star i.d. numbers are present
1 if star i.d. numbers are in catalog file
2 if star i.d. numbers are in file
Logical*4 MPROP=t True if proper motion is included
False if no proper motion is included
Integer*4 NMAG=1 Number of magnitudes present
Integer*4 NBENT=28 Number of bytes per star entry (PPM)
*Integer*4 NBENT=32 Number of bytes per star entry (PPMra)