====== Chart, Coordinates Setting ======
From the menu: **Setup -> Chart, Coordinates**
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The Chart, Coordinates Setting has six tabs:
  * [[chart_coordinates#chart_coordinates|Chart, Coordinates]]
  * [[chart_coordinates#field_of_vision|Field of Vision]]
  * [[chart_coordinates#projection|Projection]]
  * [[chart_coordinates#object_filter|Object Filter]]
  * [[chart_coordinates#grid_spacing|Grid Spacing]]
  * [[chart_coordinates#object_list_setting|Object List Setting]]

===== Chart, Coordinates =====

==== Chart Setting ====
{{  en:documentation:chart_coordinates.jpg|}}
Here, you can specify the coordinate system used for the chart.
The four available systems are:
  * Equatorial coordinates
  * Azimuthal coordinates
  * Galactic coordinates
  * Ecliptic coordinates

==== Type of coordinates ====
//**Precession, nutation and aberation recognition**//  
Your choice here determines which type of coordinates SkyCharts will display for a selected object on  the **[[status_bar#right|status bar]]**, on the bottom of the chart.
If you don't check the **Expert mode**, you can choose in the groupbox **Type of coordinates** from four options:
  * **Apparent true equator, ...**
  * **Mean of the date ...**
  * **Mean J2000 ...**
  * **Astrometric J2000 ...**
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{{  en:documentation:chart_coordinates_expert.jpg|}}
In **Expert mode** you can specify more details :
  * **Equinox** year (from -20000 to 20000)
  * **Epoch** year (from -20000 to 20000)
  * **Proper motion** checkbox to correct positions for the given epoch
  * **Mean position** or **True position** for //Nutation// and //aberration//. 
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----
Fast ways to make simple changes to the chart coordination system are from the menu by **Chart -> Coordinate Sytem -> [[menuchart#coordinate_system|[Your Choice]]]**, or directly on the chart by the icons in **[[left_bar#coordinate_system_group|coordinate system group]]**.
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===== Field of Vision =====
{{  en:documentation:chart_fov.jpg|}}
Here you can specify eleven ranges as the Field of Vision (numbered from 0 to 10).

For each range you can specify the minimum FOV in degrees, which automatically will become the maximum for the preceding range.

The first range minimum is 0.0° and last range maximum is 360° (which funny enough appears as 0.0°), these values cannot be modified.

These ranges are listed at bottom of all the **[[catalog|Catalog]]** dialog box tabs and also are used with the **[[chart_coordinates#Projection|Projection]]**, **Object Filter** and **Grid spacing** tabs. 
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Changing the FOV itself can be done from the menu by **Chart -> [[menuchart#Field_of_Vision|Field of Vision]]** or directly on the chart by the icons in **[[right_bar#The_Field_of_Vison_Group|the field of vison group]]**. A very precise FOV can be manually set by the FOV part in the dialog box from the menu **View -> [[position_and_field_of_vision#field_of_vision_fov|Field of Vision (FOV)]]**.
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===== Projection =====
{{  en:documentation:chart_projection.jpg|}}
For every FOV range you can choose from four projection types:
  * **ARC** Arc length. This is the default projection up to 180°. It corresponds to the projection of a Schmidt camera.
  * **TAN** Tangent. Corresponds to the projection of a picture obtained with a telescope or a photographic lens. The tangent projection has a great distortion for fields larger than 45° and diverge for 90°
  * **SIN** Sine. Used to display images in radio-astronomy. The sine projection overlaps at more than 90°.
  * **CAR** Cartesian. The projection between 180° and 360°. It is of no great interest, apart from the fact that it can display very large field of views.
{{en:documentation:projection_mode.png|  }} by E. Griessen, AIPS memo 27

===== Object Filter =====
{{  en:documentation:chart_object_filter.jpg|}}
By this tab you can configure magnitude limits to display stars and deep sky objects based upon the FOV of your chart.

The **Stars Filter** can be:
  * disabled. (only practical with the smaller FOVs), 
  * automatic. By this you can specify a magnitude as **Naked eye reference**,
  * manual. Now you can specify a magnitude limit for every FOV range. 
A funny excercise: There's no technical problem to disable the stars filter in combination with a large **[[catalog#CDC_Stars|active star catalog]]** (i.e. HST GSC), a high value for //field number max// (i.e. 6) and a **[[menuchart#field_of_vision|FOV]]** of 20 degrees. Now you can see why a disabled Stars filter in a large FOV is not very convenient.
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{{en:documentation:chart_object_filter_manual.jpg|}}\\ 
**Deep Sky Filter** can be:
  * disabled (only practical with the smaller FOVs), 
  * manual. Here you can specify the magnitude limit for every FOV range.

You can also filter large deep sky objects specifying the maximum dimension in minutes.

===== Grid Spacing =====
{{  en:documentation:chart_grid_spacing.jpg|}}
By this tab you can set the grid spacing for every FOV range.
  * **Degree** is for the spacing altitude or declination direction 
  * **Hour** is for the azimuth or right ascension direction 

You can enable or disable the grid display for every FOV range.

You can enable or disable the display of a compass, you also can adjust its size or disable it.
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You can enable or disable the display of grids from the menu by **Chart -> Lines / Grid -> [[menuchart#Lines_-_grid|[Show coordinate grid/add equatorial grid]]]** 
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===== Object List Setting =====
{{  en:documentation:chart_objects.jpg|}}
By this tab, you determine which object types are to be filtered from your chart to your **[[Object_List|Object List]]**.
Click on the {{en:documentation:i46.png|}} icon from the **[[main_bar#Objects List|main bar]]** to retrieve your filtered list of objects displayed on the chart.
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