GALACTIC DB

The Galactic DB was constructed from the 1997 Hipparcos Catalogue. The Bayer Flamsteed codes and common names were added by cross-referencing the Hipparcos or Henry Draper number with the HD-DM-GC-HR-HIP-Bayer-Flamsteed Cross Index.

The entries in the catalogue which did not possess a Parallax, Spectra or Magnitude were ignored.

The format of the fields within the file is described in the following table.

FIELD NAME

FORMAT DESCRIPTION
Hipparcos Number Decimal Number
Henry Draper Number Hexadecimal Number - A value of 0xFFFFFFFF indicates that a HD Number does not exist.
Durchmusterung Number 32 bit Hexadecimal Number coded as follows :
 
BIT Meaning
32 0 - Positive declination zone
1 - Negative declination zone
31-30 0 - Bonner DM Number
1 - Cape Photographic DM Number
2 - Cordoba DM Number
17-24 Declination zone
1-16 Running Number

A value of 0xFFFFFFFF indicates that a DM Number does not exist.
Bayer-Flamsteed Code Four 16 bit Hexadecimal numbers

Number 1 : Flamsteed number
Number 2 : Bayer Number
Number 3 : Constellation ID ( legal values 0 - 88 arranged alphabetical order)
Number 4 : Greek letter ( legal values 0 - 23 arranged alphabetical order)

A value of 0xFFFF indicates that the value does not exist.
Spectra Three 8 bit Hexadecimal numbers

Number 1 : Alpha-numeric character  'O', 'B', 'A', 'F', 'G', 'K', 'M', 'C', 'R', 'N', 'm', 'g', 'k'
Number 2 : Bits 1-4 contain subclass in range 0 - 9. Ignore bits 5-8
Number 3 : Bits 1-4 contain size in range 0 - 6 ( Ia, Ib, II, III, IV, V, VI). Ignore bits 5-8.
Right Ascension Two decimal numbers + 1 Floating Point

Number 1 : Hours
Number 2 : Minutes
Number 3 : Seconds
Declination Two decimal numbers + 1 Floating Point

Number 1 : Degrees ( positive and negative values)
Number 2 : Arcmin
Number 3 : Arcsec
Parallax Floating Point number in milli-arcsec
Be warned that some of these are negative - See below for explanation.
Apparent Magnitude Floating Point number
Common Name Text String

To convert Parallax to distance use the following formula :

Distance in Parsecs = 1000 / Parallax ( in milli-arcsec)

1 Parsec = 3.26 Light years.

BE WARNED THAT SOME OF THE PARALLAX VALUES FROM THE HIPPARCOS CATALOGUE ARE NEGATIVE AND WILL CONSEQUENTLY PRODUCE A NEGATIVE DISTANCE. THIS OCCURS BECAUSE THE CALCULATED PARALLAX VALUE IS SMALLER THAN THE ASSOCIATED ERROR AND HENCE THESE ENTRIES SHOULD BE IGNORED.

To convert Apparent Magnitude to Absolute Magnitude use the following formula :

Absolute Magnitude = Apparent Magnitude - ( 5.0f x log10( distance/ 10.0f)

People are free to re-use this table for any application, commercial or otherwise.