User manual

Furthermore, it is possible to give in the target field, the name of an asteroid or a comet
so that SkyBot replaces it by its celestial position on the mentioned date. To do so, it is
mandatory to press the button “Get coord. for this object+epoch…”.
5.2.10 Adding a personal server
The “server selector” window can be adapted to your own servers. It is then possible to
define a personal server that will add a tab and a form. To do so, you need to create a
small file that will contain information like the name, the description, the web address,
some parameters and then restart Aladin by indicating on the command line the file
name:
java –jar Aladin.jar –glufile=yourFile
Example of description file:
%ActionName MyServer
%Aladin.Label Test
%Description This is an example of a server
%URL http://my.web.site /my/base/query?yy=$1&xx=$2
%Param.Description $1=Parameter 1
%Param.Description $2=Parameter 2
%ResultDataType Mime(image/fits)
The full syntax is described in the Aladin FAQ (http://aladin.u-
strasbg.fr/java/FAQ.html#Glu).
Now that we described the two main windows of Aladin in detail, we will now present
the different additional windows.
5.3Adjusting the pixels dynamic
Button pixel
Menu: Image => Pixels contrast
Short key: Ctrl+M
Aladin is implementing an algorithm that renders best the astronomical images
contrast. They are often characterized by a large pixel dynamic and sometimes abnormal
values (detector’s borders, saturation, unknown values). However, the monochrome (or
false colours) visual output can only take 256 values on the current computers. Hence,
Aladin performs a resampling of pixels in order to apply a threshold: all the pixel values
that are below the low threshold value will be displayed in white while all the one above
the high threshold value will be black, and intermediate values will be converted to
values between 0 and 255 in a linear way. The autocut algorithm gives a good contrast
on “interesting” pixels, most of the time.
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