SkyChart III Updates

The latest update to SkyChart III is 3.6.4, released on 14 February 2004. Release 3.6.4 adds some new features, and fixes a number of bugs that were present in previous versions. Both Macintosh and Windows users should download and install this update. For a complete list of bug-fixes and feature improvements provided by this update, see the Release Notes section below.

This update is free for all registered SkyChart III users. But, please note: release 3.6.4 requires the release 3.6 CD-ROM! If you are running a version of SkyChart III older than 3.6, you must first order an upgrade to release 3.6, then apply the 3.6.4 patch. Registered SkyChart III users can order the release 3.6 CD-ROM upgrade from our on-line store at a discount price of $19.95 plus shipping.

To download the release 3.6.4 update, please enter the e-mail address under which you registered your copy of SkyChart III. If you have not yet registered yourself, you can click here to do so now.

Your registered e-mail address:

For SkyChart III owners who do not wish to upgrade to release 3.6, the previous update (release 3.5.1) is still available by clicking here.

Mac OS X users please note: this update requires Mac OS X version 10.2 ("Jaguar") or higher. It will not run on any earlier version of Mac OS X -- if you are running Mac OS X 10.0.x or 10.1.x, you should not download or install this update!

Mac OS 8 - 9 users please note: release 3.6.3 is the last update of SkyChart III that supports "Classic" Mac OS. There will be no further development of SkyChart III for Mac OS 8 - 9 after release 3.6.3!

Release Notes - release 3.6.4 (14 February 2004)

  1. This release brings the code base of the English-language version up to sync with the newly released Spanish-language version. A number of changes were made to support better internationalization/localization:

    • The decimal-point character is now locale-specific; decimals are displayed as "," in European locales, and "." in North America. (The computer's regional settings are used to determine the locale.) Decimal points in text import files and settings files are always assumed to be the US (".") decimal-point character, for consistency. [Note: this functionality is only present in the Windows version of SkyChart III; we're still trying to make it work on Mac OS X.]

    • All strings in data files, and settings descriptions in settings files, are converted to Windows Latin-1 encoding before being written to disk. This ensures that accented and other european-language characters will translate properly between Mac and Windows.

    • A case-sensitive search for an object name is now sensitive to both case and diacritics (e.g. accents, umlauts, etc). When case is ignored, diacritics are also ignored - e.g. a search for "Jupiter" will also find "Júpiter", and a search for "Saturn" will also find "Säturn".

  2. In the chart legend, the full names of deep sky objects are being displayed, instead of abbreviations.

  3. In the "Object Info" window, a number of text strings and buttons were rearranged. The object type for the Sun is now displayed as "Star"; for the major planets as "Planet"; for moons as "Moon". The star type for single stars is now simply listed as "Star".

  4. For years outside 1600 - 2100 A.D., the program uses new expressions for the precession of the equinox provided by W. M. Owen of JPL. These new expressions should provide realistic results for a much wider interval of +/- 500,000 years from J2000. (The previous expressions "blew up" and displayed highly unrealistic results after roughly 10,000 years from J2000.) For the time period 1600 - 2100 A.D., the previous (IAU 1976) expressions for precession are still used.

  5. Previous versions of the Windows installer for SkyChart III installed a 16-bit version of the uninstall application (UnWise.exe). This update replaces it with the 32-bit version.

  6. Fixed a crash in the Mac OS X version that occurred when moving the mouse inside a progress-bar dialog.

  7. Removed timing code in the Mac OS X version that was causing a performance-profiling dialog to appear sporadically.

  8. The Mac OS X version of SkyChart III can now launch properly on Macs with 2.0 GB of RAM or more installed. The Mac OS X installer/updater application should no longer display a warning on Macs with more than 2.0 GB of RAM. (This warning can safely be ignored, however.)

  9. The Mac OS X version now has the main window's "close" button enabled; clicking it quites the application. The "Quit" menu command has moved from the File menu to the "SkyChart III" menu, for better conformance with Apple's Mac OS X interface guidelines.

Release Notes - release 3.6.3 (3 Aug 2003)

  1. This is the last update of SkyChart III that supports Mac OS 9. There will be no further development of SkyChart III for Mac OS 9 after this release.

  2. The event-handling code in the Mac OS X version has been rewritten to use the new Carbon Event Manager APIs. This increases processor efficiency on Mac OS X. It also allows the chart window to resize dynamically (instead of using a "rubber-band" outline).

  3. Animation and telescope control on Mac OS X and Windows are now driven using "Timer" APIs. As a result, animation now runs consistenly at the rate of 30 frames per second regardless of processor speed; and animation and telescope communications no longer stop when a modal dialog window is present, or when a menu is pulled down. Real-time animation updates at the rate of 1 frame per second, increasing processor efficiency.

  4. SkyChart III now has a contextual or "right-click" menu, letting the user select commands related to object or area of the chart where the mouse was clicked. On Mac OS 9 (or any Mac with a single-button mouse), the contextual menu is accessed by holding the "control" key down while clicking the mouse.

  5. On Windows XP, the program no longer crashes when selecting an object as the telescope target.

  6. On Mac OS 9, the name of the target object should now appear correctly in the "Telescope Control" window when a new target object is selected.

  7. On Mac OS X, the titles for the "Telescope Control" and "Object Info" dialogs now appear correctly. The initial size of the main SkyChart window now more acccurately fits the size of the screen.

  8. In the Windows version, LPT ports are no longer listed as options in the connection port menu, in the "Telescope Connection" dialog box. There are no currently supported telescopes which can connect via LPT ports; all of them communicate via COM ports only.

  9. The mailing address for Southern Stars Systems in SkyChart III's splash screen and in the documentation has been updated to reflect our new physical address.

Release Notes - release 3.6.2 (15 April 2003)

  1. Fixed problem with magnitudes in chart legend appearing as "-0.5" instead of their correct values when those values are non-integers.

  2. In the Windows version, changed telescope slew speed buttons (on Windows) from pushbutton controls to radio button controls to match the Mac version, and to provide visual feedback for the telescope's slew speed.

  3. In the Mac OS X version, fixed a problem with checkmarks not appearing in submenus.

  4. For deep sky objects that have outlines, SkyChart III now accurately determines if the mouse has been clicked inside the object or not. This eliminates some confusing behavior in previous releases ("Object Info" window not appearing when a deep sky object was clicked, or vice-versa).

Release Notes - release 3.6.1 (16 December 2002)

  1. Communication problems with later-model Meade Autostar and LX-200 GPS telescopes have been fixed. SkyChart III now supports directional slewing and variable slew rates with these models, and uses "long-format" coordinates for higher precision in getting and setting the position of Meade LX-200, LX-200 GPS, and Autostar telescopes.

  2. Communication problems with Celestron NexStar GPS telescopes have been addressed. SkyChart III now supports directional slewing and variable slew rates with these models, and uses 32-bit position commands for higher precision in getting and setting the position of these telescopes. Known problems with these telescopes:

    • In order to work properly with SkyChart III, your NexStar's hand controller must be running firmware version 1.6 or higher; contact Celestron for an upgrade if it is not.

    • NexStar GPS telescopes may spontaneously stop a directional slew after 8 - 30 seconds even though the mouse button has not yet been released from the directional slew arrows in SkyChart III's Telescope Control window.

    • After executing a directional slew, the telescope may take a few seconds to return to normal equatorial or alt-az tracking mode.

    These problems appear to be with Celestron's firmware, but are still under investigation.

  3. Communication problems with certain BBox-compatible encoders have been resolved.

  4. The "Red Screen" mode has been improved. When this mode is turned on, SkyChart III now adjusts the main video display's gamma table, making the entire screen (instead of just the contents of the chart window) appear in red. This functionality works in Mac OS X, Mac OS 9, and most Windows video cards, but may not be supported by some Windows video drivers, however.

  5. Galaxy symbols now appear in their correct shape and orientation, instead of always as horizontally-oriented ovals.

  6. The "Traditional Constellations" import file provided by David Lazaroff has been included in this release; the updater will place a copy in the "Sample Import Files" folder.

  7. Errors in the documentation regarding the format of constellation line import files has been fixed.

  8. Stars with Tycho-2 catalog (TYC) numbers greater than 1000-xxxx-x now have their catalog numbers displayed correctly in the "Object Info" dialog.

  9. A problem with grey squares appearing in the on-line documentation in Mac OS X 10.2 ("Jaguar") has been fixed.

  10. The Mac OS X and Windows versions of the program no longer appear to use 100% of the CPU when the program is running idle.

Release Notes - release 3.6 (19 August 2002)

  1. This is the first new CD-ROM release of SkyChart III since early 1999. The new CD-ROM contains two Macintosh versions of the installer on the CD-ROM: one for Mac OS 8.6 - 9.2, and one for Mac OS X. The Windows installer on the CD-ROM works with requires Windows 98, ME, NT, 2000, or XP.

  2. The Mac OS X version has a new set high-resolution icons for the application, its datafiles, and the CD-ROM.

  3. SkyChart III's object database has been completely rewritten. The format has been changed to include more data for each object. In addition, the data have been taken from more recent sources:

    • The stellar database now includes the complete Hipparcos and Tycho-2 catalogs; hence stellar positions, proper motions, and distances should be much more accurate. Stellar distances are now exclusively computed as a function of trigonometric parallax; no effort was made to compute stellar distances from spectroscopic parallax.
    • The Guide Star Catalog data is now based on version GSC-ACT (1.3) of the Hubble Guide Star catalog. This is a re-reduction of the original Guide Star Catalog data using positions and proper motions for reference stars from the Hipparcos/Tycho star catalogs. It significantly reduces the systematic position errors present in the original version (1.1) of the Guide Star Catalog used in previous editions of SkyChart III. In addition, Guide Star Catalog objects present in the much more accurate Tycho-2 catalog were removed from SkyChart III's database, to prevent duplication.
    • Variable stars have variability data taken from the 1998 General Catalog of Variable Stars.
    • Binary star orbital data are taken from the 2002 Sixth Catalog of Visual Binary Star Orbits.
    • Open cluster data are taken from Wilton S. Dias's Catalog of Open Cluster Data and G. Lynga's 1987 Catalog of Open Cluster Data.
    • Globular cluster data are taken from William E. Harris's 1999 catalog of Globular Clusters in the Milky Way.
    • Bright diffuse nebula data are taken from a list compiled by Charles Turner, based on data from Sky Catalog 2000.0 and other sources.
    • Planetary nebula data are taken from the 1992 Strasbourg-ESO Catalog of Galactic Planetary Nebulae.
    • Galaxy data are taken from the 2002 Principal Galaxy Catalog.

    The database format has been changed to allow for the greater precision provided by the new catalogs. Stellar magnitudes and color indices are now stored to milli-magnitude precision; proper motions are stored with floating point precision. This last change corrects a bug in previous versions, where stellar proper motion was computed incorrectly due to integer truncation of values.

    The new database format also contains several quantities not present in previous versions. For stars, SkyChart III's database now stores spectral types; double star position angles; and variable star periods, epochs, and variability types. Multiple stars now have orbital elements, where available. For deep sky objects, the database now stores major- and minor-axis apparent sizes, position angles, and morphological classifications for galaxies.

    The database size limit has been raised from 16,000 files/16,000 objects per file to 65,535 files/65,535 objects per file. This increases the maximum total number of objects from 256 million to 4.2 billion!

  4. SkyChart III can now compute the orbital motion of binary stars. Binary star components now have their separations and position angles displayed in the "Object Info" dialog, and by animating the chart at several years per step, you can "watch" one component orbit the other. Two new settings files, "Orbiting Alpha Centauri" and "Sirius B", demonstrate this functionality.

    The following animated GIF file shows the orbit of Alpha Centauri, as viewed from a point in space near Alpha Centauri B. The animation advances at the rate of 1 frame every six months; the pair takes 80 years to complete one orbit. From this vantage point, the constellations are distorted from their familiar shapes, and the Sun appears as a first-magnitude star in Cassiopeia.

    The orbit of Alpha Centauri

  5. Outline data for roughly 100 of the brightest diffuse nebulae have now been included in the database; SkyChart III can now draw these objects with outlines, instead of the previous square diffuse nebula symbol.

    The following chart of the Veil Nebula in the constellation Cygnus illustrates the new nebula outlines:

    The Veil Nebula

  6. The "Object Info" dialog has been updated to display the new data included in SkyChart III's object database. Star proper names are listed before their catalog numbers, and stars with constellation designations (e.g. Alpha Centauri or R Coronae Borealis) now have their names fully spelled out.

  7. The "Find Object..." dialog now lets you search for stars with Bayer letters by entering the English spelling of the letter. For example, to search for Alpha Centauri, you'd simply type "Alpha Centauri". There's no longer any need to remember or use SkyChart's bayer-letter abbreviations (e.g. $a for Alpha, $b for Beta, etc.) although these abbreviations will still work.

  8. The "Find Object..." dialog now contains an option to search for objects by their catalog number. This is significantly faster, and should produce fewer false hits. For example, searching for "M 1" should immediately find the Crab Nebula, instead of other objects whose names contain the text "M 1" (such as M 11, or M 110).

  9. SkyChart III now computes the positions of artificial earth satellites using the full-precision SGP4/SDP4 satellite orbit models. This should result in much more accurate satellite position predictions. (Technical note: SkyChart III stores the value of a satellite's B* atmospheric drag coefficient in as its "mass". If the program seems to be reporting unsually large masses for earth satellites, that's normal; the "mass" is really the drag coefficient.)

    This chart shows the satellite COSMOS 2239 passing across the moon as seen from upstate New York, USA, on the evening of February 18th, 2002. With the new full-precision orbit models, SkyChart III can now make accurate satellite predictions like this.

    COSMOS 2239 passing across the moon

  10. The program now corrects for atmospheric refaction differently. When the "Refraction" correction is turned on (in the "Precision" dialog box), the horizon line in the chart window is now drawn at its true altitude (i.e. corrected for refraction), rather than at its apparent altitude (i.e. as specified in the "Precision" dialog box). The horizon altitude specified in the "Precision" dialog box now always refers to the altitude of the apparent horizon; the true horizon will be drawn slightly lower than this if the "Refraction" correction is turned on. The refraction correction option is now turned on by default.

  11. Object rise/set times are now computed using the refracted (true) horizon altitude if the "Refraction" box is checked in the "Precision" dialog. The program also now takes into account the size of an object's apparent disk when computing its rise/set times: they are now computed as the precise instants that the object's upper limb appears on the horizon. These changes can make several minutes' difference in the case of the Sun and Moon, and should result in rise/set times that agree much better with local newspaper predictions. Rise/set times are now displayed to one-second precision to reflect the higher accuracy, although (due to unpredictably varying local atmopheric conditions and horizon topography) they should not be trusted to more than a minute.

    Occasionally, when predicting the rise/set times of a "fast-moving" object (particularly the Moon), SkyChart III would give the rise/set time for that object on the previous or following day, rather than on the current day. This bug has been fixed; rise/set times always refer to an instant during the current local day.

  12. The viewer's longitude and latitude as displayed in the "Location" dialog box are now explicitly labelled as E/W (East/West) and N/S (North/South). This was determined to be less confusing than the previous convention of positive longitude = east and negative = west.

  13. The values for ΔT, the difference between Universal Coordinated Time (UTC) and Terrestrial Dynamic Time (TDT), have been updated for the years 1998-2006. The program should now provide much more accurate estimates of ΔT for times near the present. Also, the local sidereal time is now correctly computed as a function of UTC when the time scale used for display is TDT instead of UTC.

  14. The Windows version of SkyChart III now draws planet and solar-system-object icons in black when the "Use Color" option is off and the sky is drawn in white. As a result, planet symbols which did not previously appear because they were drawn in white, should now appear on the screen and in printouts. (This bug did not affect the Mac OS versions.)

  15. If the viewer was not located on the earth, SkyChart III would not correct for aberration even if the "Aberration" box (in the "Precision" dialog, under the "Computation" menu) was checked. This has been fixed: the program now always corrects for aberration when this box is checked.

  16. SkyChart III now corrects for geocentric parallax correctly when the precession epoch is set to something other than J2000. Previous versions failed to precess the viewer's geocentric coordinates correctly, resulting in a small error in the apparent positions of objects near the earth (e.g. the moon, or especially artificial earth satellites).

  17. The program now computes the apparent magnitude of the planet Mercury correctly; its magnitude predictions now agree with the Astronomical Almanac's. (In previous versions, the formula used to compute Mercury's magnitude contained a small error.)

  18. A number of places where the program could display angles like 18° 59' 60.0" and times like 00:00:-0 have been fixed.

  19. Previous versions of SkyChart III could fail to draw some database files containing stars when making charts of large areas of the sky with a very faint magnitude limit. This bug is has been fixed.

  20. The AstroLib C source code library is no longer distributed on the SkyChart III CD-ROM. You can, however, download a copy from the SkySight open source page.


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This page was last updated on 16 February 2004.