A license friendly NGC/IC objects database
Credits: Mattia Verga https://github.com/mattiaverga/OpenNGC
OpenNGC is a database containing positions and main data of NGC (New General Catalogue) and IC (Index Catalogue) objects. Unlike other similar databases which are released with license limitations, OpenNGC is released under CC-BY-SA-4.0 license, which allows the use for a wider range of cases.
For information about data fields contained in the database, please see the file NGC_guide.txt.
OpenNGC has been built by merging data from:
NASA/IPAC Extragalactic Database http://ned.ipac.caltech.edu/ This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.
SIMBAD Astronomical Database http://simbad.u-strasbg.fr/simbad/ This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France
HEASARC High Energy Astrophysics Science Archive Research Center http://heasarc.gsfc.nasa.gov/ We used several databases from HEASARC such as messier, mwsc, lbn, plnebulae, lmcextobj and smcclustrs.
Where incongruences between catalogs was found we used NED as source.
Some common names are taken from internet sources like Wikipedia.
NOTES ON OBJECT DATA
All object types: coordinates are taken from NED; magnitudes are taken from SIMBAD if not specified otherwise.
Galaxies (G | GGroup | GPair | Gtrpl): data about major axis, minor axis, position angle, surface brightness and Hubble classification is taken from LEDA; if major axis or minor axis data is not available from LEDA, then it's taken from SIMBAD (usually from 2MASS measures, so they're referred to IR, not visual; in this case a note is added to the object).
Star clusters (OCl | GCl | *Ass | Cl+N): where available, diameters and position angle are taken from the following HEASARC tables: mwsc [central_radius]; smcclustrs [major_diameter, minor_diameter, position_angle]; lmcextobj [major_axis, minor_axis, position_angle].
Planetary Nebulae (PN): data is imported from HEASARC plnebulae table, fields used are opt_diameter, umag_cstar, bmag_cstar, vmag_cstar, name, pk_name, iras_name, alt_name_1, alt_name_2, alt_name_3, alt_name_4. B_Mag and V_Mag are imported from LEDA, while J, H, K are from Simbad.
Nebulae (HII | Neb | EmN | RfN | SNR): where available, major and minor axis are taken from HEASARC lbn table [large_dimension], [small dimension]. If data source is different then is specified in object notes.
The 'addendum' folder contains a separate catalog file with notably objects that are not part of the NGC or IC catalog. These objects may be of some interest to amateur astronomers.
Note that two Messier objects (M40 and M45) haven't got any NGC or IC designation, so they're listed only in the addendum.
For a basic Python interface to OpenNGC data, see PyOngc project at https://github.com/mattiaverga/PyOngc.