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The object names in the MASC catalog generally conform to the object name format used by the SIMBAD object database (see the SIMBAD web site for more information). A number of the fields below were obtained from the USNO Washington comprehensive catalog database (WCCD) (see the USNO Catalog web site for more information). In the description below, 'b' stands for a blank character and 'N' stands for a single (0-9) digit and 'C' stands for a single character.

The following fields are contained within each entry in the MASC catalog:

Hipparcos Catalog Number
Hipparcos ID format is 'HIPbNNNNNN', where 'NNNNNN' is a 6 digit number. This is a searchable field. This field was obtained from the USNO WCCD.
Tycho-2 Catalog ID
Tycho-2 Catalog ID format is 'TYCbNNNNbNNNNNbN'. The last 'N' digit represents a component designation, with '1' being the primary component. This is a searchable field. This field was obtained from the USNO WCCD.
Common or Historical Name
This is a searchable field. This field was obtained from the SIMBAD astronomical database.
Examples: 'Capella' or 'Polaris'
Bayer or Flamsteed Designation (not both)
Bayer format is 'aaabCCC', where 'aaa' stands for the greek letter abbreviation, (ordered by decreasing brightness), and 'CCC' is the constellation abbreviation. Flamsteed format is 'NNNbCCC', where NNN is a 1-3 digit number ordered by increasing RA within the constellation 'CCC'. May have component designations included. This is a searchable field. This field was obtained from the SIMBAD database. Examples: '2 Per', 'alf Ori', 'bet01 Tuc', '77 Psc A', 'nu. Psc'.
General Catalog of Variable Stars (GCVS) ID
GCVS format is 'AAbCCC' or 'VNNNbCCC' where, 'AA' are two letters, 'CCC' is the constellation abbreviation, and 'NNN' is a 1-3 digit number. This is a searchable field. Examples: CH Cyg. This field was obtained from the SIMBAD database.
Henry Draper Catalog ID
HD format is 'HDbNNNNNNbC', where 'NNNNNN' is a 6 digit ID and 'C' is an optional component designation. This is a searchable field. This field was obtained from the SIMBAD database. Examples: 'HD 100286 J', 'HD 3114', 'HD 236450'.
Bright Star Catalog ID
BS format is 'HRbNNNN', where 'NNNN' is a 1-4 digit number (1-5647). This is a searchable field. This field was obtained from the SIMBAD database. Examples: 'HD 1708'.
Fifth Fundamental Katalog (FK5) ID
FK5 ID format is 'FK5bNNNN', where 'NNNN' is a 1-4 digit number. This is a searchable field. This field was obtained from the SIMBAD database.
Smithsonian Astrophysical Observatory (SAO) ID
SAO ID format is 'SAObNNNNNN', where 'NNNNNN' is a 1-6 digit number. This is a searchable field. This field was obtained from the SIMBAD database.
Bonner Durchmusterung (BD) Catalog ID
BD ID format is 'BD+DDbNNNNNNC' or 'BD-DDbNNNNNNC', where 'DD' is the declination zone, 'NNNN' is a 1-4 digit number, and 'C' is a component designation. This is a searchable field. This field was obtained from the SIMBAD database. Examples: 'BD+16 2332', 'BD+22 2421'.
CD ID format is 'CD-DDbNNNNNC', where 'DD' is the declination zone, The suffix 'C' is an additional star designation. This is a searchable field. This field was obtained from the SIMBAD database. Example: 'CD-49 2465', 'CD-61 6916', 'CD-33 16575B'.
Cape Durchmusterung (CPD) Catalog ID
CPD ID format is 'CPD-DDbNNNNNC', where 'DD' is the declination zone, 'NNNNN' is a 1-5 digit number, and 'C' is a component designation. This is a searchable field. This field was obtained from the SIMBAD database. Examples: 'CPD-80 3', 'CPD-57 10277', 'CPD-49 735A'.
V (F7.2)
For stars listed in the Hipparcos main catalog this a Johnson V magnitude (field H5). If the Hipparcos V magnitude was not available, then the median magnitude in the Hipparcos photometric system (field H44 - Hp) was used for some of the stars in double or multiple systems. The source of the Hp magnitude is from the Hipparcos component file (HIP_DM_C.DAT). For stars observed only by Tycho2 this is a Tycho V magnitude, which closely approximates the Johnson V magnitude. The V Flag field indicates whether it is an Hipparcos (H), a Tycho-2 (T), or an Hipparcos Hp (P) measurement. The V magnitude is a searchable field
V Flag (C1)
This flag indicates whether the V magnitude measurements are from the Hipparcos main catalog (H), the Hipparcos component (P) file (HIP_DM_C.DAT) or the Tycho-2 catalog (T).
Spectral Type (C15)
The Spectral Type field was obtained from the SIMBAD database during July-September of 2002 and updated in early 2005. Spectral types for selected Tycho-2 entries were obtained from the WCCD, if not available from SIMBAD. See Appendix D of the SIMBAD Users Guide for further spectral type coding information.
Multiple Flag (N1)
Multiple System Flag. This flag was obtained from the USNO WCCD, where: 1 = Entry is likely single, 2= Entry is likely double.
Variable Flag (N1)
This field is the same as the Hipparcos Course Variability Flag. This flag was obtained from the USNO WCCD, This flag refers to the Hipparcos catalog entries only and is the same as the Hipparcos H6 flag. This flag is blank for all Tycho-2 entries. It indicates that the object is variable, in Hp, at the level of:
  • 1: < 0.06 mag,
  • 2: 0.06 - 0.6 mag,
  • 3: > 0.6 mag.