# Configuring &kstars;

&kstars; has many configuration options, which you can access by opening the Display Options window, either with the configure toolbar icon, or selecting Configure &kstars;... from the Settings menu, or by pressing &Ctrl;o. The window is depicted below:

Display Options Window Display Options Window

The Display Options window is divided into five tabs: Catalogs, Guides, Solar System, Colors, and Advanced. Note that changes you make in this window are reflected immediately in the map, but that the changes are not committed until you press the Ok button.

In the Catalogs tab, you determine which object catalogs are displayed in the map. The SAO star catalog also allows you to set the faint magnitude limit for stars, and the magnitude limit for displaying the names and/or magnitudes of stars. Below the stars section, there is a box containing a list of checkboxes for the available deep-sky object catalogs. You can add your own custom object catalogs by pressing the Add Custom Catalog button, which will open a File Dialog, so that you can point it to your catalog data file. For detailed instructions on preparing a catalog data file, see the `README.customize` file that ships with &kstars;.

In the Solar System tab, you can specify whether the Sun, Moon, planets, comets and asteroids are displayed, and whether the major bodies are drawn as circles or actual images. You can also toggle whether solar system bodies have name labels attached, and control how many of the comets and asteroids get name labels. There is an option to automatically attach a temporary trail whenever a solar system body is tracked, and another to toggle whether the color of the planet trail fades into the background sky color.

The Guides tab lets you toggle whether non-objects are displayed (&ie;, constellation lines, constellation names, the Milky Way contour, the celestial equator, the ecliptic, the horizon line, and the opaque ground). You can also choose whether you would like to see Latin constellation names, IAU-standard three-letter abbreviations, or constellation names using your local language.

The Colors tab allows you to set the color scheme, and to define custom color schemes. The tab is split into two panels:

The left panel shows a list of all display items with adjustable colors. Click on any item to bring up a color selection window to adjust the color. Below the list is the Star Color Mode selection box. By default, &kstars; draws stars with a realistic color tint according to the spectral type of the star. However, you may also choose to draw the stars as solid white, black or red circles. If you are using the realistic star colors, you can set the saturation level of the star colors with the Star Color Intensity spinbox.

The right panel lists the defined color schemes. There are four predefined schemes: the Default scheme, Star Chart, which uses black stars on a white background, Night Vision, which uses only shades of red in order to protect dark-adapted vision, and Moonless Night, a more realistic, dark theme. Additionally, you can save the current color settings as a custom scheme by clicking the Save Current Colors button. It will prompt you for a name for the new scheme, and then your scheme will appear in the list in all future &kstars; sessions. To remove a custom scheme, simply highlight it in the list, and press the Remove Color Scheme button.

The Advanced Tab provides fine-grained control over the more obscure behaviors of &kstars;.

The Correct for atmospheric refraction checkbox controls whether the positions of objects are corrected for the effects of the atmosphere. Because the atmosphere is a spherical shell, light from outer space is bent as it passes through the atmosphere to our telescopes or eyes on the surface. The effect is largest for objects near the horizon, and actually changes the predicted rise or set times of objects by a few minutes! In fact, when you see a sunset, the Sun's actual position is already well below the horizon; atmospheric refraction makes it seem as if the Sun is still in the sky! Note that atmospheric refraction is never applied if you are using Equatorial coordinates.

The Use animating slewing checkbox controls how the display changes when a new focus position is selected in the map. By default, you will see the sky drift or slew to the new position; if you uncheck this option, then the display will instead snap immediately to the new focus position.

If the Attach label to centered object checkbox is selected, then a name label will automatically be attached to an object when it is being tracked by the program. The label will be removed when the object is no longer being tracked. Note that you can also manually attach a persistent name label to any object with its popup menu.

There are three situations when &kstars; must redraw the sky display very rapidly: when a new focus position is selected (and Use animated slewing is checked), when the sky is dragged with the mouse, and when the time step is large. In these situations, the positions of all objects must be recomputed as rapidly as possible, which can put a large load on the CPU. If the CPU cannot keep up with the demand, then the display will seem sluggish or jerky. To mitigate this, &kstars; will hide certain objects during these rapid-redraw situations, as long as the Hide objects while moving checkbox is selected. The timestep threshold above which objects will be hidden is determined by the Also hide if timescale greater than: timestep-spinbox. You can specify the objects that should be hidden in the Configure Hidden Objects group box.