[ index | applet | help | notes | download ]


AJ's Cosmic Thing version 1.1 help notes

Iterations

The iteration type setting menu (Static plot, Step five minutes, and so on) in the Display Sequence controls sets the Thing's iterations, allowing you to trace the movements of objects through the sky over minutes, hours, days, or months. The smaller iterations are mostly useful for quickly determining when an object of interest is going to be somewhere you can observe it, while the latter are generally more useful for illustration of celestial mechanics — demonstrating the nature of the movements of the planets, and the seasonal changes in visibility of the constellations.

The sidereal periods are useful primarily for working out the movements of objects in our solar system — a single sidereal day is the amount of time it takes the earth to rotate back to the same position relative to the stars — roughly a normal solar day minus four minutes. So if you set any of these iteration periods, the stars and deep sky objects will not move from iteration to iteration, but the planets, the sun, and the moon will move against the background of stars.

Longitude and latitude

For casual observing (and this is all the Thing's precision really supports anyway), a precise longitude and latitude are quite unnecessary — you can usually get adequate results with the position of a settlement reasonably close to your location, so if you can find this quickly from a gazeteer, you need do no more. The Thing will also generally guess a longitude not wildly far from yours when you set it up, deriving this from your timezone offset. Latitude, however, it can't do anything about, as the JVM doesn't support deriving this from your system in any way.

Time zones and daylight saving time

Though the new JVM does support more sophisticated DST rules, I haven't had time to write code to make use of it (sadly, my employer requires me to write a lot of C++ these days, which makes me kinda cranky, but I digress), so, like the old Thing, version 1.1 just always uses standard time. This does mean for those of you in jurisdictions that observe DST, you will have to make the odd mental adjustment by an hour (or, in some regions two). For example, during the summer, most of the EST zone (Greenwich minus five, or most of Eastern North America) observes DST, and actually displays on their clocks Greenwich minus four. So when the Thing says 19h00 EST, it means the same thing as 20h00 EDT.

Mouse clicks and modifiers

There are a few rather unintuitive commands in the interface. They are

  • In the main plot and in constellation plots, click on any object to get an image of and additional information about the object. For stars, the Thing just displays illustrations of the spectral type, while for deep-sky objects and planets, it displays CCD images of the object, if it has them available (for most of the deep sky objects, it does not, sadly).
  • In the main plot, and in constellation plots, Ctrl-click on any fixed object (everything but solar system objects) to bring up a new constellation window showing the constellation that contains it. In constellation windows, Ctrl-clicking on an object in the constellation already displayed will do nothing.
  • In constellation plots, shift-click on any fixed object to recenter the window on the constellation containing the object.

That's all, have fun.


[ index | applet | help | notes | download ]

The author blogs at The Accidental Weblog.

See also Gienah, a newer system loading larger catalogues.