Welcome to Personal Sky Chart, PSC, version 1.3.

Now supports control for Meade LX200 and compatable telescopes

PSC has been chosen by PDA Pointer for their Jan 2003 Editor's Choice Best of the Best in the category Medical, Science and Education.
We were also pleased to find PSC in Software Showcase, March 2003 Sky and Tel page 64.

The primary goals of PSC are to:

replace bulky printed star charts while traveling or in the field;
seamlessly include moving objects such as moons and asteroids;
be complete for a visual observer using about a 18" scope.

The result is a program that displays over 15 million objects: all stars, deep sky objects and asteroids to Mag 15, as well as the principle moons of Mars, Jupiter Saturn and Uranus. Catalogs include YBS, NGC, IC, UGC, PPM, SAO, HD and GSC and the latest asteroid elements from Harvard Minor Planet Center. Display calculations require only seconds even with all objects loaded.

Other handy features include:

full support for Earth satellites in TLE 2-line format.
draw your own annotation and labeling;
set location from hundreds of built-in choices or define your own;
define and place any number of rectangular and elliptical rotatable eyepieces;
draw and limit displayed objects to those visible above a local horizon profile;
handy calculators for astronomical coordinate systems, field-of-view and focal length;
display classic or Rey constellation figures;
Night at a Glance shows when objects rise and fall over night;
handy red night vision mode;
create lists of favorite targets;
watch asteroids move across the sky over time;
add your own objects in an easy CVS-like database format;
16 levels of undo and redo
save and reload all settings with simple XML format preferences file;
control LX200-compatible telescope.

Theory of Operation

PSC performs all computations to full precision, always opting for accuracy over speed. Nevertheless, times are not unacceptable even on small PDAs with no hardware floating point due to extensive look-ahead and field-culling techniques. Fixed objects are first sorted into roughly 1 degree sky patches based on their J2000 coordinates. These patches are indexed for fast random access and each is also sorted by decreasing brightness within each patch. So large areas are fast because each patch is quickly abandoned (assuming reasonable limiting magnitude) and small areas are fast because only the required patches are searched. No further computation is required unless Topo or EOD options are turned on.

Things are not quite so easy for asteroids because they move. They are sorted according their brightest possible magnitude which can be computed for all time from their orbital elements alone. An asteroid's ephemeris is recomputed if 1) it can ever be as bright as the current limiting magnitude setting and 2) it could conceivable enter the field of view based on their last known location and velocity (which implies they must all be computed at least once, which you can witness as you look at dimmer magnitudes).

The small progress bar in the lower left will help you get a feel for these algorithms in practice. In general, load only the catalogs of interest and either don't look deep or use a small field of view. The limiting magnitude PSC chooses automatically for any given field size is a good compromise, but can be changed if desired using the light bulbs in the toolbar.