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
of Integrated Databases
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.
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
-- 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.
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).
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.
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.
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.
-- 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.
Story of the Most Accurate and Complete Double Star Database
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.
don't realize it, but many stars move enough over time that a
component may appear in one place as originally observed decades
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.
of this matching was automated, but when that process failed the
rest were done by hand using a special-purpose program.
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.
the star was 180 degrees away from where it really
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
The result is a
highly-corrected database that can be counted on to be
much more accurate than the original catalogs.