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diff --git a/doc/kstars/altvstime.docbook b/doc/kstars/altvstime.docbook new file mode 100644 index 00000000..0438b0cb --- /dev/null +++ b/doc/kstars/altvstime.docbook @@ -0,0 +1,90 @@ +<sect1 id="tool-altvstime"> +<title>Altitude vs. Time Tool</title> +<indexterm><primary>Tools</primary> +<secondary>Altitude vs. Time Tool</secondary> +</indexterm> + +<screenshot> +<screeninfo> +The Altitude vs. Time Tool +</screeninfo> +<mediaobject> + <imageobject> + <imagedata fileref="altvstime.png" format="PNG"/> + </imageobject> + <textobject> + <phrase>Altitude vs. Time Plotter</phrase> + </textobject> +</mediaobject> +</screenshot> + +<para> +This tool plots the altitude of any objects as a function of time, +for any date and location on Earth. The top section is a graphical +plot of altitude angle on the vertical axis, and time on the horizontal +axis. The time is shown both as standard local time along the bottom, +and <link linkend="ai-sidereal">sidereal time</link> along the top. +The bottom half of the graph is shaded green to indicate that points +in this region are below the horizon. +</para> +<para> +There are a few ways to add curves to the plot. The simplest way to +add the curve of an existing object is to simply type its name in the +<guilabel>Name</guilabel> input field, and press Enter, or the +<guibutton>Plot</guibutton> button. If the text you enter is found in +the object database, the object's curve is added to the graph. You +can also press the <guibutton>Browse</guibutton> button to open the +<link linkend="findobjects">Find Object Window</link> to select an +object from the list of known objects. If you want to add a point +that does not exist in the object database, simply enter a name for +the point, and then fill in the coordinates in the +<guilabel>RA</guilabel> and <guilabel>Dec</guilabel> input fields. +Then press the <guibutton>Plot</guibutton> button to add the curve for +your custom object to the plot (note that you have to pick a name that +does not already exist in the object database for this to work). +</para> +<para> +When you add an object to the plot, its altitude vs. time curve is +plotted with a thick white line, and its name is added to the listbox +at the lower right. Any objects that were already present are plotted +with a thinner red curve. You can choose which object is plotted with +the thick white curve by highlighting its name in the listbox. +</para> +<para> +These curves show the objects' Altitude (angle above the <link +linkend="ai-horizon">horizon</link>) as a function of time. When +a curve passes from the lower half to the upper half, the object has +risen; when it falls back to the lower half, it has set. For example, +in the screenshot, the minor planet <firstterm>Quaoar</firstterm> is +setting at around 15:00 local time, and is rising at about 04:00 local +time. +</para> +<para> +The Altitude of an object depends on both where you are on Earth, and +on the Date. By default, the Tool adopts the Location and Date from the +current KStars settings. You can change these parameters in the +<guilabel>Date & Location</guilabel> Tab. To change the Location, +you can press the <guibutton>Choose City...</guibutton> button to open +the <link linkend="setgeo">Set Geographic Location</link> Window, or +enter Longitude and Latitude values manually in the input fields, and +press the <guibutton>Update</guibutton> button. To change the Date, +use the <guilabel>Date</guilabel> picker widget, then press +<guibutton>Update</guibutton>. Note that any curves you had already +plotted will be automatically updated when you change the Date and/or +Location. +</para> + +<tip> +<para>Exercise:</para> +<para> +Plot the Sun's Altitude curve. Make sure the geographic location is not +near the equator. Change the Date to some time in June, and then again to +sometime in January. You can see easily why we have seasons; in the +winter, the Sun is above the horizon for less time (the days are shorter), +and its altitude is never very high. +</para> +</tip> + + +</sect1> + |