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Data Catalogs

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Data Catalogs

Why is the deep-sky and stellar database different in Deep-Sky Planner?

The data catalogs that compose the database are taken from professional, peer-reviewed results (see exceptions below.)  Catalogs are viewed as different research results because the goals of the studies that produce each catalog differ.  Researchers use differing techniques to study various aspects of the objects that appear in their catalog(s).  This accounts for the difference in data between catalogs, even for the same object.  Furthermore, catalogs may contain a type of data not found in others. For this reason, Deep-Sky Planner treats data for each cataloged object uniquely.  If a catalog includes cross references for an object, these other object designations appear in Deep-Sky Planner reports as cross references.

Exceptions: The term 'catalog' is not accurate for the Caldwell, Herschel 400, Herschel 2, and Messier objects; however, they are treated as catalogs within Deep-Sky Planner because they are in extensive use by astronomers.  The data for these objects is taken primarily from the NGC2000.0 catalog.

Better data presentation

Reports contain the essential data present in all catalogs (RA, Declination, constellation, star atlas cross references, etc), but importantly, the database remains true to original catalog contents so that reports contain the additional data unique to each catalog.  For example, a report of Abell or Hickson Galaxy Clusters includes the number of member galaxies, and a report of Monella's Globular Clusters includes the concentration class.  These data are presented as needed - not the one-size-fits-all presentation.

Making catalog data easier to use

Professional data catalogs are readily available via the Internet and those available change constantly, but placing a catalog in Deep-Sky Planner's database is not entirely trivial.  The data is formatted for the database but helpful features in the user interface and reports are also updated when a new catalog is added to the product.

For example, most deep-sky object catalogs contain angular size data though some don't.  The original catalogs use different units of measure for angular size data and different precision - planetary nebulae in PNG are measured in arcseconds while Zwicky galaxy clusters are measured in hundredths of square degrees.  The range of angular size values present in a catalog also varies greatly.  The user interface helps you to search by:

• permitting you to select a range of angular sizes only for catalogs that contain that data
• permitting you to select a range of angular sizes within the limits of the catalog (limits are shown for the catalog)
• permitting entry in the appropriate unit of measure and precision for the selected catalog (both are shown)

In addition, the report generated from the search only shows angular size if it is present in the catalog, and size data is shown in the appropriate unit of measure and precision for the catalog.  Other types of data are treated similarly (magnitude, angular separation of double stars, etc.)  Taken together, these features help to make the catalog data more useful to the end-user.

If you would like to request the addition of a catalog to the Deep-Sky Planner database, please send your request to Support.

NGC 2000.0: The Complete New General Catalogue and Index Catalogues of Nebulae and Star Clusters by J.L.E. Dreyer, edited by Roger W. Sinnott. (c) 1988 Sky Publishing Corp. Reproduced with permission of the publisher.

Special thanks to Sky Publishing Corporation for providing updates to the Caldwell catalog and to the NGC2000.0 catalog.