# Configuring &kstars;

## Setting the Geographic Location

Here is a screenshot of the Set Geographic Location window: Changing the Geographic Location Set Location Window

There is a list of over 2500 predefined cities available to choose from. You set your location by highlighting a city from this list. Each city is represented in the world map as a small dot, and when a city is highlighted in the list, a red crosshairs appears on its location in the map.

It isn't practical to scroll through the full list of 2500 locations, looking for a specific city. To make searches easier, the list can be filtered by entering text in the boxes below the map. For example, in the screenshot, the text Ba appears in the City Filter box, while M has been entered in the Province Filter box, and USA is in the Country Filter box. Note that all of the cities displayed in the list have city, province, and country names that begin with the entered filter strings, and that the message below the filter boxes indicates that 7 cities are matched by the filters. Also notice that the dots representing these seven cities in the map have been colored white, while the unmatched cities remain gray.

The list can also be filtered by location in the map. Clicking anywhere in the world map will show only those cities within two degrees of the clicked location. At this time, you can search by name, or by location, but not both at once. In other words, when you click on the map, the name filters are ignored, and vice versa.

The longitude, latitude and time zone information for the currently-selected location are displayed in the boxes at the bottom of the window. If you feel that any of these values are inaccurate, you can modify them and press the Add to List button to record your custom version of the location. You can also define a completely new location by pressing the Clear Fields button, and entering the data for the new location. Note that all fields except the optional State/Province must be filled before the new location can be added to the list. &kstars; will automatically load your custom locations for all future sessions. Please note, at this point, the only way to remove a custom location is to remove the appropriate line from the file `~/.kde/share/apps/kstars/mycities.dat`.

If you add custom locations (or modify existing ones), please send us your `mycities.dat` file so that we can add your locations to the master list.

## Setting the Time

When &kstars; starts up, the time is set to your computer's system clock, and the &kstars; clock is running to keep up with the real time. If you want to stop the clock, select Stop Clock from the Time menu, or simply click on the Pause icon in the toolbar. You can make the clock run slower or faster than normal, or even make it run backward, using the time-step spinbox in the toolbar. This spinbox has two sets of up/down buttons. The first one will step through all 83 available time steps, one by one. The second one will skip to the next higher (or lower) unit of time, which allows you to make large timestep changes more quickly.

You can set the time and date by selecting Set Time... from the Time menu, or by pressing the time icon in the toolbar. The Set Time window uses a standard &kde; Date Picker widget, coupled with three spinboxes for setting the hours, minutes and seconds. If you want to re-synchronize the simulation clock back to the current CPU time, just select Set Time to Now from the Time menu.

&kstars; can accept very remote dates beyond the usual limits imposed by QDate. Currently, you can set the date between the years -50000 and +50000. We may extend this range even further in future releases. However, please be aware that the accuracy of the simulation becomes more and more degraded as more remote dates are examined. This is especially true for the positions of solar system bodies.

## The Configure &kstars; Window

The Configure &kstars; window allows you to modify a wide range of display options. You can access the window with the configure toolbar icon, or by selecting Configure &kstars;... from the Settings menu. The window is depicted below:

Configure &kstars; Window Configure &kstars; Window

The Configure &kstars; window is divided into five tabs: Catalogs, Guides, Solar System, Colors, and Advanced.

In the Catalogs tab, you determine which object catalogs are displayed in the map. The Stars section 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, the Deep-Sky Objects section controls the display of several non-stellar object catalogs. By default, the list includes the Messier, NGC and IC catalogs. You can add your own custom object catalogs by pressing the Add Custom Catalog button. 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 colored 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 orbit trail whenever a solar system body is tracked, and another to toggle whether the color of the orbit 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 its 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 subtle 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 Earth's 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.

## Customizing the Display

There are several ways to modify the display to your liking.

- Select a different color scheme in the Settings Color Schemes menu. There are four predefined color schemes, and you can define your own in the Configure &kstars; window.

- Toggle whether the Toolbars are drawn in the Settings Toolbars menu. Like most KDE toolbars, they can also be dragged around and anchored on any window edge, or even detached from the window completely.

- Toggle whether the Info Boxes are drawn in the Settings Info Boxes menu. In addition, you can manipulate the three Info Boxes with the mouse. Each box has additional lines of data that are hidden by default. You can toggle whether these additional lines are visible by double-clicking a box to shade it. Also, you can reposition a box by dragging it with the mouse. When a box hits a window edge, it will stick to the edge when the window is resized.

- Choose an FOV Symbol using the Settings FOV Symbols menu. FOV is an acronym for field-of-view. An FOV symbol is drawn at the center of the window to indicate where the display is pointing. Different symbols have different angular sizes; you can use a symbol to show what the view through a particular telescope would look like. For example, if you choose the 7x35 Binoculars FOV symbol, then a circle is drawn on the display that is 9.2 degrees in diameter; this is the field-of-view for 7x35 binoculars.

  You can define your own FOV symbols (or modify the existing symbols) using the Edit FOV Symbols... menu item, which launches the FOV Editor:

  Field-of-View Symbols Editor
  FOV Symbol Editor

  The list of defined FOV symbols is displayed on the left. On the right are buttons for adding a new symbol, editing the highlighted symbol's properties, and removing the highlighted symbol from the list. Note that you can even modify or remove the four predefined symbols (if you remove all symbols, the four defaults will be restored the next time you start &kstars;). Below these three buttons is a graphical preview display showing the highlighted symbol from the list. When the New... or Edit... button is pressed, the New FOV Symbol window is opened:

  New Field-of-View Symbol
  New FOV Symbol

  This window lets you modify the four properties that define a FOV symbol: name, size, shape, and color. The angular size for the symbol can either be entered directly in the Field of View edit box, or you can use the Eyepiece/Camera Tabs to calculate the field-of-view angle, given parameters of your telescope/eyepiece or telescope/camera setup. The four available shapes are: Circle, Square, Crosshairs, and Bullseye. Once you have specified all four parameters, press Ok, and the symbol will appear in the list of defined symbols. It will also be available from the Settings | FOV menu.