User manual

Object location
In order to trace astronomical objects to their precise location, Aladin is based on the
astronomical solution linked to the image, e.g. a centralized tangential projection. Most
of the time, images are given with an astronomical solution (this is the case in particular
for the one in the FITS format). If this is not the case, for example for a JPEG image
given by the user, it is possible to compute its astronomical solution (menu: Image =>
Astrometrical calibration – see5.8). Sometimes, objects do not exactly overlap with the
image, either because their locations are approximate or because the astrometrical
solution is uncertain.
Activating planes
Planes shown in the view are those that were activated in the stack. One can hide one of
the planes temporarily, or even hide the background image (see 5.1.1).
Switching to the next image
Menu: View => Next image
Short key: Tab
If the stack has several images, it is possible to switch quickly from one image to the
other by simply activating the corresponding image plane. Automatically, all the
graphical planes (drawings and catalogues) that can be superimposed on the image will
be activated. The menu item “View => Next image” or the “TAB” key do the same action.
This can be particularly useful when in full screen or simple window mode (see below).
Cube or “animated sequence"
For an image data “cube” (see 5.10 - associations or FITS cubes), the plane in the stack
holds several images that will be displayed in the view as an “animated sequence”, i.e.
image after image, with a tunable delay (400ms by default) that can be changed in the
plane properties. The view, in which the cube is visualised the cube shows a pace
controller overdrawn on the image. This controller uses usual conventions from tape
recorder (pause, play, backward, forward,) Below the controller; a ruler displays the
location of the current image in the cube. This ruler, as well as the controller can be
manipulated with the mouse.
Translucent image
It is also possible to display an image in a
translucent way above another image. This is in
particular useful when the image to display in
translucence is smaller than the background
image. In order to activate the translucence of an
image, one should use the magenta coloured
ruler that appears below the plane logo for the
image that can be projected. Once the ruler is
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