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The Endeavour application now has a large subset of the fourth US Naval Observatory CCD Astrograph Catalog (UCAC4). The subset contains over 30 million stars to magnitude +15.0.
Here's an example of the difference. This is the M13 area using the Tycho-2 catalog:
And this is the M13 area with the UCAC-4 subset:
There are now three additional chart presets: Telescope (small), Telescope (medium), and Telescope (large). These use the UCAC-4 data along with deep-sky objects to show a representation of the sky as seen, under dark skies, in three size ranges of telescope (approximately 4", 8", and 16" apertures respectively).
UCAC-4 stars are displayed when all of these criteria are met:
If large star catalogs are enabled, but the scale is too low or the magnitude limit is too bright, you'll get the Tycho-2 catalog instead. Also, as with the Tycho-2 catalog, the UCAC-4 catalog does not contain distance information, so it's not available when your "source location" is remote (away from the Sun). For star atlas views near the Sun, though, enjoy over 30 million new stars!