What Types of Map can you Display in C2A?

C2A lets you display two different kinds of map:

Maps of the Field type. In this kind of map, north is at the top of the screen by default regardless of your location on the sky. This makes it easy to create field maps when preparing for observation. You can apply symmetries and rotations to views of the field type, and these will be applied to all displayed fields.		When a map of the field type is displayed, the symbol above is displayed in the top left of the view. The small yellow dash indicates the direction of North.
Maps of the Horizon type. In this kind of map, the field is oriented so that the nearest horizon will be horizontal in the view displayed on the screen. This type of map lets you easily display a given horizon to identify, for instance, the large scale pattern of the brightest stars of a constellation.		When a map of the Horizon type is displayed, the symbol above appears in the top left of the view. The number shown in the symbol is the current azimuth of the view.

Once a view type has been selected, it remains (even after zooms and translations) until it is explicitly changed by the user. For maps of the “Field” type, the orientation stays the same; and for “Horizon” type views the map is always oriented so that the perpendicular to the nearest horizon points towards the bottom of the screen.

You can at any time move from one type of view to the other in several ways:

By using the F and H shortcuts on your keyboard. F lets you switch the current map type to Field and H to Horizon. The center of the field as well as its value stay unchanged.

By using the Maps tab of the Options dialogue box. In this dialogue box, you just select the Field or the Horizon option. If you choose the “Horizon” option, you must then specify the azimuth of the direction you want. It can be South, North, East or West, or any azimuth you specify. Once the choice has been made, clicking the OK button in the dialogue box displays a map showing a global view of the requested azimuth (a 180° view with the requested azimuth in the centre of the screen).

By using the S, N, E, W, "Field" and "Horizon" buttons on the main tool bar. Clicking one of the 4 cardinal points buttons lets you immediately display a global view of the requested azimuth. The field value used is defined in the “Global field” option on the Field tab of the options dialogue box. Values between 1° and 200° are possible. Clicking the Field button does not change the zoom level but reorientates the map so that the north will be systematically towards the top (as mentioned above, you can apply symmetries and rotations to views of the Field type). Clicking the Horizon button does not change the zoom level but reorientates the map so that the nearest horizon will be horizontal in the view displayed on the screen.

By using the S, N, E, W keys (cardinal points). The result is the same as with the buttons on the main tool bar.

By using the G key (Global). Pressing this key produces a display of the Field type with a field value equal to that defined in the Global field option in the Field tab of the options dialogue box. Values between 1° and 180°are possible.

By clicking the two small rectangles Field and Horizon at the top left corner of the map.

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