;+
; NAME:
;  hd_mag_to_flag
;
; PURPOSE: (one line)
;  Decode HD catalog's special magnitude labels into their meaning.
;
; DESCRIPTION:
;  HD catalog encodes some non-magnitude information in the 
;  magnitude field.
;
;  Decode HD catalog's magnitude labels into their meaning.
;  '20' becomes 'Nebula?'
;  '30' becomes 'Variable?'
;  '40' becomes 'Nova?'
;  '50' becomes 'Cluster?'
;  For any other values, '' is returned.
; 
; These decodings are taken from the Vizier HD ReadMe file.
;
; CATEGORY:
;  Star catalogs
;  
; CALLING SEQUENCE:
;  Flag = hd_mag_to_flag(mag)
;
; INPUTS:
;  Mag  -- Stellar magnitude as listed in HD catalog.  Scalar.
;
; OPTIONAL INPUT PARAMETERS:
;  None
;  
; KEYWORD INPUT PARAMETERS:
;  None
;
; KEYWORD OUTPUT PARAMETERS:
;  None
;
; OUTPUTS:
;  None
;  
; COMMON BLOCKS:
;  None
;
; SIDE EFFECTS:
;  None
;
; RESTRICTIONS:
;  None
;
; EXAMPLE:
;  print, hd_mag_to_flag(30d)
;    [Prints 'Variable?']
; 
; MODIFICATION HISTORY:
;  Written  19-Oct-2005 by Henry Throop, SwRI
;  Modified 28-Feb-2006 by HBT. Improved documentation and formatting.
;-
function hd_mag_to_flag, mag

  flag = ''
  if (double(mag) eq 20d) then flag = 'Nebula?'
  if (double(mag) eq 30d) then flag = 'Variable?'
  if (double(mag) eq 40d) then flag = 'Nova?'
  if (double(mag) eq 50d) then flag = 'Cluster?'

  return, flag
end