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(Above image courtesy of ClearDarkSky.com)

In mid-2001, Attilla Danko, a software designer for Nortel Networks in Canada hit upon a brilliant idea:

Using data from the Canadian Meteorological Center, I created highly-specialized weather forecasts for astronomers for over 1400 observatories and observing sites across North America. [...] ClearDarkSky has become the premier weather forecasting service to its audience.

An example of a Clear Sky Chart forecast is shown above. The most important line to astronomers is typically the first colored line which shows the forecast cloud cover for the next two days, which is why some astronomers refer to the diagram as the "Clear Sky Clock."

In September of 2005, Joshua Lynch released a Dashboard widget for the Mac (MacOS X 10.4.3 or later) that would display the "Clear Sky Clock" on the Dashboard of the MacOS. However, it had a bug with parsing clear sky chart weather stations that prevented our campus observatory's site from being selectable for display. After discovering the widget was relased under the GNU General Public License, I set about remedying this problem and with the original author's permission, adding new features to the widget.

Download current version of Clear Sky Clock widget (Version 1.5)

New Features

The key new features I added since Joshua Lynch's version 1.0 release of the Clear Sky Clock widget are:

1. Proper parsing of weather station names with periods and parentheses in their names.
2. Half-size mode: Click on the "Toggle Size" link on the screen and the widget will switch between full-size and half-size. When a widget is half-sized it occupies one-quarter of the area and is still readable:
   
   
3. Built-in Legend: If you click on the clear sky chart image, a legend will appear underneath, describing the meaning of the various colors on the clear-sky chart. Click on the clear sky chart image again, the legend disappears. The legend looks something like this:
   
   

Version History

Version 1.5 (October 3, 2011) [Download here]

• Released by Juan Cabanela
• Added support for site names with accented characters. I fixed a problem that prevented sites with non-ASCII characters, such as those accented characters in French and Spanish site names, from showing up. The name may not look correct in the pull down menu with a diamond where the accented character should be, but the site will work.

Version 1.4 (August 11, 2011)

• Released by Juan Cabanela
• Fixed an apparent incompatibility with Snow Leopard and Lion. Version 1.3 would not properly parse the list of locations in a state and would return no choices. This made it impossible to use this widget without some preferences hacking (or having set it up BEFORE the glitch was introduced... which is why I didn't see it. I had configured under Leopard and thus the widget continued to work fine.

Version 1.3 (October 13, 2008)

• Released by Juan Cabanela
• Built-in Legend: After an emailed discussion with Attilla Danko, the creator of Clear Sky Charts, I have gotten formal permission to include his code for the legend in this version of the widget. If you click on the clear sky chart image, a legend will appear underneath, describing the meaning of the various colors on the clear-sky chart.
• Built-in Link to Clear Sky Chart Site Page: When you are displaying a clear sky chart for a given ground station, a link is present at the bottom of the page which will take you to the Clear Sky Chart webpage for this ground station, allowing you to view much more detailed information about how the forecast was developed (and clicking on his version of the Clear Sky Chart actually brings up the "future" cloud cover maps which can be quite illuminating).

Version 1.2 (October 10, 2008)

• Beta-testing version by Juan Cabanela. Never publically released.
• New Widget Icon
• Half-size mode: Click on the "Toggle Size" link on the screen and the widget will switch between full-size and half-size. This saves considerable screen real estate.
  

Version 1.1 (October 8, 2008)

• Beta-testing version by Juan Cabanela. Never publically released.
• Fixed a bug that prevented the loading of any Clear Sky Chart for sites containing parentheses or periods in their names.
• Removed "Copyright" statements, since the common interpretation of Copyright is inconsistent with the GNU General Public license. This move was made with Joshua Lynch's permission.

Version 1.0 (September 25, 2005)

• Released by Joshua Lynch
• Loads Clear Sky Chart to MacOS Dashboard.

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