User manual

centre (too wide a star), a message will be display to say that the clicked location will be
taken as it is.
Tips:
 It can be useful to perform the “symmetry” of the DSS image in order to get closer to
the orientation of the image to calibrate ( Image => Symmetry)
 It is better to only display the bright stars with little proper motion. Using a filter an
a catalogue ease the pointing of corresponding sources, for example:
$[pos.pm;pos.eq.dec]<3 mas/yr && $[pos.pm;pos.eq.ra]<3 mas/yr
&& $[phot.mag*]<17 { draw circle(-$[phot.mag*]) }
 It is possible not to load a catalogue; the celestial coordinates will then be those
deduced for the DSS image calibration. The calibration precision will then be lower.
 Using the translucence (Menu “image => Transparency level”) to visualise the image
that just got calibrated, onto the DSS image, lets you check simply the quality of the
calibration.
Redo and undo
During the creation process or the adjustment of the calibration, it is possible to go back
to the former solution by using the “Redo” and “Undo” buttons at the bottom of the
window.
Calibration of a catalogue
Aladin also offers the possibility to calibrate or recalibrate a catalogue. This corresponds
to the computation, for each source, of its celestial position. Select the catalogue plane in
the stack and use the menu “catalogue => Astrometrical Calibration…”. The interface and
methods are the same as for the image.
Moving with the mouse
If you are using the calibration method by parameters (1
st
board), it is possible to move
directly the sources from a catalogue to calibrate in the view in order to visualise the
result directly. For this you need to click and move a source with the mouse; the other
sources will follow. Along the move, the calibration parameters will be automatically
adjusted. The move is validated with the “CREATE” or “MODIFY” button which
computes the new celestial positions according to the indicated offset.
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