Detailed Description of Catalogue VII/7A/

Url: http://astro.u-strasbg.fr/cgi-bin/Cat?VII/7A/
------------------------------------------------------------------------

VII/7A              Lynds' Catalogue of Dark Nebulae  (LDN)     (Lynds 1962)
================================================================================
Catalogue of Dark Nebulae
     Lynds B.T.
    <Astrophys. J. Suppl. Ser. 7, 1 (updated version) (1962)>
    =1962ApJS....7....1L
================================================================================
ADC_Keywords: Nebulae

Description:
    This catalog is an updated version from the published version. The
    catalog was based on the red and blue prints of the National
    Geographic - Palomar Observatory Sky Atlas. The catalog contains
    positions, both equatorial and galactic for the centers of dark
    nebulae. Values for the cloud sizes are given in square degrees, and
    estimates of their opacity are given. The updated catalog is ordered
    by galactic longitude and includes cross references to the published
    catalog and Barnard Object numbers associated with the clouds.

File Summary:

------------------------------------------------------------------------

  FileName      Lrecl  Records   Explanations

------------------------------------------------------------------------

ReadMe             80        .   This file
ldn                92     1791   The LDN Catalogue

------------------------------------------------------------------------

See also:
    VII/191 : Catalogue of Southern Dark Clouds (Hartley+ 1986)
    J/A+AS/113/325 : Distance measurements of some Lynds nebulae (Hilton+ 1995)

Byte-by-byte Description of file: ldn

------------------------------------------------------------------------

   Bytes Format  Units   Label    Explanations

------------------------------------------------------------------------

   1-  4  I4     ---     LDN     *[1/1802]?+ Catalogue number from
                                    original published version (ApJS 7, 1)
   6-  7  I2     h       RAh      Right Ascension 1950 (hours) of Cloud Center
   9- 12  F4.1   min     RAm      Right Ascension 1950 (minutes)
      16  A1     ---     DE-      Declination 1950 (sign) of Cloud Center
  17- 18  I2     deg     DEd      Declination 1950 (degrees)
  20- 21  I2     arcmin  DEm      Declination 1950 (minutes)
  23- 28  F6.2   deg     GLON     [0/360[ Galactic longitude of Cloud Center
  30- 35  F6.2   deg     GLAT     Galactic latitude of Cloud Center
  37- 43  F7.3   deg2    Area     Area, in square degrees, of the Cloud
      45  I1     ---     Opacity *[1/6]?=0 Opacity class
  47- 49  I3     ---     ID      *[0/416] Identification Number.
  51- 54  I4     ---     Seq      [1/1791] Running Number in this version
                                    of the Catalogue (ordered by GLON)
  56- 59  I4     ---     Lynds2  *Number that B. Lynds assigned when
                                    the updated catalogue was created.
  61- 92  A32    ---     Barn    *Cross-identifications with Barnard Objects.
                                    (up to 8 Barnard numbers in format 8A4)

------------------------------------------------------------------------

Note on LDN: Compared to the printed edition:
     => 15 "duplicated" LDN numbers were removed: 184, 366, 457, 465, 924,
        1025, 1318, 1342, 1344, 1413, 1575, 1592, 1593, 1603, 1792
     => there are 4 nebulae without a LDN number at the end of the table
Note on Opacity:
     The opacity is on a scale of 1 (lightest) to 6 (darkest).
     in cases where small dark clouds are within large, lighter
     clouds, both or all clouds have been listed separately.  But
     they will be identified with the same ID (bytes 48-50) number.
Note on ID:
     Entries with null identification number are objects lying in
     the general obscuration of the Milky Way.
Note on Barn:
     Barnard designations are made by a number followed by a letter;
     see Barnard E.E., 1927, Carnegie Inst. Washington,
     "A photographic Atlas of selected regions of the Milky Way"
Note on Lynds2:
     Number that B. Lynds assigned when the updated catalogue was created.
     The significance of this number is unknown. Also, it is not a unique
     number throughout this version of the catalogue.

------------------------------------------------------------------------

Historical Notes:
 * July 1979, by Theresa A. Nagy, from NASA document R-SAW-7/79-13,
   "Documentation for the machine-readable version of Lynds' Catalogue
    of Dark Nebula":

    The initial version of the machine-readable version of the Lynds'
    Catalogue of Dark Nebulae was received from the University of
    Maryland. This version was obtained from the author and represents
    an updated version of the original published catalogue (1962
    Astrophysical Journal Supplement #64). The major differences between
    these two versions are as follows:
      1. The galactic coordinates have been revised.
      2. Some of the original observations of "clouds" have been deleted.
      3. There are 1791 objects in the updated version and there were
         1802 objects in the original published catalogue.

    The original version, as such, does not exist in machine-readable
    form except in the cases where we have added the Barnard
    identification(s) to the appropriate objects. Since a correlation
    had to be made from the original catalogue numbers to obtain the
    Barnard cross-identifications (data obtained from a table in the
    original publication), these original numbers were retained.

    The version of the catalogue as received from the University of
    Maryland was updated as follows:
      1. The catalogue was sorted by galactic longitude.
      2. A running number (Seq) was added after the sort.
      3. A cross-reference table between the old Lynds numbers and the
         Barnard numbers was made so that this information could be
         added to the machine-readable version.  Therefore, the Barnard
         numbers and the original Lynds numbers were added (one record
         had as many as eight Barnard numbers).

  * October 1991: the catalogue is prepared for the ADC CD-ROM
    "Selected Astronomical Catalogs" Vol. 1 (NASA), in directory
    /nonstell/nebulae/ldn

  * 25-Sep-1995: Description added by Gail L. Schneider [SSDOO/ADC]

  * 22-Feb-1996: James Marcout and Francois Ochsenbein, CDS)
    The previous version only contained a fraction of LDN numbers
    (about 1500 were missing). A new version 'A' of the catalogue was
    created, incorporating all original LDN numbers, with the exception
    of nebulae originally duplicated (see Note on LDN above); the columns
    were re-ordered to follow more closely the original publication.
================================================================================
(End)                  James Marcout, Francois Ochsenbein     [CDS]  22-Feb-1996

CDS Catalogue Service