In general, BBSO follows the SoHO convention (see below), except that the 
observation time will have six characters with format HHMMSS instead of four 
characters, and the miscellaneous info code will be modified to represent 
different spatial resolution and calibration data.

Example:

              1         2         3
    012345678901234567890123456789012   <=== character index
    
    bbso_halph_fi_19930820_154122.fts   <=== filename
    ---- ----- -- -------- ------ ---
      |    |    |     |      |     |
      |    |    |     |      |     |
      |    |    |     |      |    File extension (3 chars)
      |    |    |     |      |
      |    |    |     |   Observation time (6 chars, in hhmmss format)
      |    |    |     |
      |    |    |  Observation date (8 chars, in yyyymmdd format)
      |    |    |
      |    |  Miscellaneous info code
      |    |
      |   Image type code (5 chars)
      |   
    Institution code (4 chars)
    
A standard BBSO file name will consist of 33 characters (including 4 
underscore characters and a dot).

Following are a list of institutes codes:

    BBSO    Big Bear Solar Observatory
    KANZ    Kanzelhoehe Solar Observatory
    YNAO    Yunnan Astronomical Observatory
    CTAO    Catanoa Astrophys. Obs
    HSOS    Huairou Solar Observatory
    MEDN    Meudon Observatory

Miscellaneous info code consist of 2 characters:
1) "f" for full disk data and "r" for region data, i.e. partial frame
2) "i" - uncalibrated data; "l" - DC and FF corrected; "r" DC, FF and contrast enhanced data