User manual

catalogue with only XY positions
If you load a table or catalogue without celestial positions but with two columns
representing the XY coordinates that Aladin could detect (based on the column names
and/or the attached UCDs), the calibration window of the catalogue is instantaneously
opened, inviting you to create a calibration for these sources.
Saving a recalibrated catalogue
Once you save a catalogue, after its recalibration, Aladin systematically adds two
columns with the celestial position for each source.
5.9RGB colour image builder
Icon: rgb
Menu: Image => RGB image builder…
Aladin can build a true colour image
from 2 or 3 images with grey levels. To
do so, the first component will be
affected to the red colour, and the
second and third images will be
affected to green and blue components
respectively. The true colour image
will be saved in a plane of the stack.
Tip: If the mouse cursor is on the RGB
plane logo that was created, the 3
logos for the 3 original images appear
with the colour of their respective
component.
Resampling
In order to have the image pixels corresponding to the same locations on the sky, Aladin
does a resampling on two of the images according to the astrometrical position in the
third one. This image is then called the “reference image”. By default, the reference image
will be the image for which the angular pixel size is the smallest. This resampling is
based on the “nearest neighbour pixel” algorithm (see Erreur : source de la référence non
trouvée - resampling)
Access to the window
The window to generate a colour image
can be accessed either with the menu
“Image => Create a RGB image…” or
with the “rgb” button.
The default choice of the images for
each component depends on the state of
the stack. If there are only two or three
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