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ellipsoidal errors for the location, arrows for which the location and size are relative to
proper motion values …
Showing a filter in the stack
The filter is displayed as a peculiar plane in the stack and applies to all catalog planes
located above the filter plane.
Using a predefined filter
Aladin has some predefined filters that correspond to the usual handlings in astronomy.
You can then select one of them and apply them instantaneously with the menu
« Catalog  Predefined filters ».
On the other hand, it is often useful to tune filter constrains and to do so, one needs to
create and edit the filtering rules manually. This is what is going to be detailed in the
following section.
Create a filter
A filter can be created with the « filter » button in the tool bar or with the menu « Catalog
 Create a filter ». Two modes can be used thanks to tabs:
 The « beginners » mode, which is like using a predefined filter (see above);
 The « expert » mode where you can edit the filtering rules by yourself.
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