(c) Skyhound

SkyTools Database Advantages

The SkyTools databases are quite different from those found in other software.  Most other software takes the data engine approach, where professional astronomical catalogs are overlaid on a chart or searched separately.  There are many inherent problems with this approach.  The user is left to decide which of the many positions is most accurate and to find the relevant data by sorting through multiple sources.  SkyTools uses integrated databases where the best data is culled from many professional catalogs and combined into a single custom database for each type of object.  The result is simplified access to object data and less cluttered charts.

Advantages of Integrated Databases

Accurate Stars to 20th Magnitude -- the Professional Edition of SkyTools comes with an Extended Star Database with over 522 million stars down to 20th magnitude. These stars have been combined from multiple sources and filtered for accuracy.  Other software can only go this deep after a time-consuming download and complicated installation of very large professional catalogs.  That, or the purchase of an expensive external hard drive with the data pre-installed.  Even then, you only have the raw, often conflicting, catalog data.

Clutter Free Charts -- in other software separate catalogs are overlaid on the charts.  Duplicates appear as an object is in more than one catalog.  Often the positions in each catalog don't match exactly, leaving a clutter where there should only be one object.  This is avoided in SkyTools by integrating the data from multiple catalogs into a single database.

Completeness -- SkyTools always gives you the best data available.  For instance, one catalog for planetary nebulae may have superior positions, but another may have superior magnitudes, and yet another may have superior sizes and morphology notes.  SkyTools brings all this data together automatically.

Accuracy -- the astronomical catalogs available today are rife with errors and inconsistencies. The author of SkyTools drew on his experience as a professional astronomer to draw together the best data to make a single entry for each object.  This is particularly important for the stellar database, where the positions and magnitudes of variable and multiple stars are often contradictory.  An enormous effort went into cross referencing the stellar data--a task that took years to accomplish.  The author spent a full year correcting the Washington Double Star catalog alone (see below).

Optimized Searching -- with so much data integrated into a single database it is possible to do exhaustive searching without having to specify which professional catalogs to search.  This includes large numbers of cross references to different designations.  For example, the Blue Planetary nebula can also be looked up as NGC 3918, He 2-74, PN G294.6+04.7, PK 294-4.1, ARO 514, or ESO 170-13.

Double Stars Expand on Charts -- no other software allows you to zoom in to any double star to see the individual component stars appear.   Long period binary stars with orbits also appear, drawn at their correct positions for the date.  If a component star is identified as a variable star in a catalog of variable stars that component will be identified with this variable star data.

Speed -- there are actually two separate databases; a reference database optimized for efficient access and searching, and a mapping database optimized for drawing charts.  The result is faster searching and faster charts.

Consistency -- you would think that an NGC galaxy is set in stone with its NGC number.  But in fact catalog errors are constantly being identified--even for the NGC catalog.  You may observe NGC 1112 only to discover years later it has been changed to NGC 1113.  With SkyTools every effort is made to keep your notes and logs consistent even as these things change.  Whatever the NGC number, your notes will still refer to the object you observed.

The Story of the Most Accurate and Complete Double Star Database

An example of the lengths the author has gone to for the highest-quality data is the double-star database.  This database draws star pairs from the WDS, CCDM, and the Tycho-2 supplement.  Care was taken to take the best data from each of these catalogs. 

People don't realize it, but many stars move enough over time that a component may appear in one place as originally observed decades ago, and another more recently.  Great care was taken to match the observations of each pair to stars with measured proper motions at their position on the date they were observed.  These stars came from the UCAC or USNO-B1 catalogs.  We found many cases where new pairs were measured years later that were actually the same stars, just in different relative positions.  

Most of this matching was automated, but when that process failed the rest were done by hand using a special-purpose program.

Above is the multiple-star system HD 8487.  The D component, marked in red in the upper-right, failed to match properly because of an inaccurate measurement.  It was easily matched to a star in the database by hand.  In this way we found and fixed many different kinds of errors. 

Sometimes the star was 180 degrees away from where it really was. 

In many cases the star pair was assigned to the wrong primary star.  A search of nearby stars usually turned up an exact match, recovering the pair. 

Many unmatched wide pairs that were missing from both the USNO-B1 catalog and the DSS images were deleted as non-existent.

In other cases there were obvious typos in either the position angle or separation that could be fixed.

By matching the component stars to the USNO-B1 database, many of them have proper motions.  With these proper motions in hand SkyTools can accurately depict the relative positions of the stars as they move over time, something no other software can do.

The result is a highly-corrected database that can be counted on to be much more accurate than the original catalogs.