NGC_COMP/IC_COMP (M0): HyperSky NGC/IC Composite Catalogs (9930607)
FILES:
ngc_comp.m0 (14328 entries), ngc_comp.ls (NGC object position-list)
ic_comp.m0 (5315 entries), ic_comp.ls (IC object position-list)
CONTENTS: HyperSky NGC/IC Composite Catalogs
DATASET: These files come in HyperSky dataset M-6, 19930607. Availability on HyperSky CD-ROM: Vol. 1 (1993)
DESCRIPTION: These files compose a special subset of objects from other existing HyperSky datasets, combined to represent the present state of knowledge of about Dreyer's NGC catalog as it exists in current major astronomical catalogs. The files were constructed by extracting and combining all NGC and IC object data from the following HyperSky catalog sets:
Set: Abbrev. Catalog Name Contributed objects: NGC IC
-----+---------+-----------------------------------------+----------------
BASE LYNGA Lynga open clusters 345 24
BASE MOSCOW Moscow globular clusters 102 2
BASE STRASBRG Strasbourg planetary nebulae 88 33
G-2 ESGC South Equatorial Galaxy Catalog 1417 230
G-2 SGC Southern Galaxy Catalog 1288 624
G-4 CGCG_RD CGCG (Zwicky) Galaxy Catalog 982 49
G-5 MCG Morphological Catalog of Galaxies 5009 2040
G-7 RC3.9a Third Reference Catalog of Bright Galaxies 3100 1126
M-3 ESOB ESO/Uppsala Survey: ESO(B) Atlas 1948 1137
N-1 LYNDS_BN Lynds' Catalog of Bright Nebulae 49 50
-----+---------+-----------------------------------------+----------------
totals: 14328 5315
The intent is to present in a single dataset all contributing catalog information on each NGC and IC object. Thus each object may be represented by several entries, one for each occurrence in the contributing catalogs. In this way, the HyperSky composite NGC/IC data make no judgement about which contributing catalog may be right or wrong. Instead, you are allowed to compare and judge all object entries for yourself.
Because of the way in which the composite data has been assembled, the composite data does not represent the complete NGC or IC catalogs. The 14327 entries in the composite NGC catalog represent about 7000 of the 7840 original NGC objects, and the the 5315 enries in the composite IC catalog represent about 3100 of the original 5389 IC objects. Many of the missing original NGC/IC objects are duplicates of other NGC/IC identifications, stars or multiple stars, or (for the IC) plate defects.
Any objects noted in the contributing catalogs as having both NGC and IC designations should also appear in both composite catalogs.
DATA: The HyperSky composite datafiles contain the following data from the contributing catalogs:
POSITION: Right Ascension and Declination are based on the contributing catalog values, precessed to equinox 2000.
MAG: As available, from the contributing catalog
IDENTIFICATION: The primary identification in the contributing catalog. This may not be the NGC or IC number. If the NGC/IC number is not the primary identification, it will appear in the following comment lines.
COMMENTS: Because of the way in which the composite catalogs have been assembled, the format of each object entry comment will depend on the contributing catalog from which it was extracted. Thus, if a comment is not clear you should consult the contributing catalog manual page for explanations.
NOTE!! The LAST line of each entry comment identifies the contributing catalog for that entry, using the abbreviations in the above table.
POSITION-LISTS: ngc_comp.ls, ic_comp.ls.
These position-lists let you locate any NGC or IC object referenced in the HyperSky NGC/IC Composite Catalog files. Because of the size of the NGC/IC catalogs, each list has three levels: a thousands menu, a hundreds menu, and finally an individual list of objects. For example, to center your HyperSky field on the position of NGC 1326B, you would select group "1000 - 1999" from the NGC_COMP.LS toplevel menu, then select group "1300" from the second-level menu, and finally select NGC 1326B from the resulting NGC object-list. List positions are for equinox 2000.
The lists are NOT complete lists of NGC/IC object positions; instead each list contains only NGC or IC objects actually in the catalog files NGC_COMP.M0 and IC_COMP.M0 (see manual page NGC_COMP.MM0 for more info). The NGC position-list contains about 7000 the 7840 total NGC objects, and the IC position-list contains about 3100 of the 5400 IC objects. Some objects appear only as combined objects (NGC 7303/4 for example), while other objects will appear multiple times with appended component letters (eg, NGC 3258A thru NGC 3285E). In general, individual components of multiple-component NGC or IC objects are retained in the lists only if component coordinates differ.
Included in the lists for most objects is a two-letter HyperSky object type code. HyperSky object type codes are discussed in online manual file DATAFILE.MAN. The following list summarizes the object type code subset used:
Gx : galaxy
C- : cluster or asterism
Co : open cluster
Cg : globular cluster
Pl : planetary nebula
Ne : emission or reflection nebula
St : star
?? : unknown or unclassified type
Remember that these lists are only position-lists; they do not display objects at the positions you select. Objects will appear at the positions you select only if you have also loaded ngc_comp.m0, ic_comp.m0 or other HyperSky datafiles that contain the appropriate NGC/IC objects.