Stacks
A stack is a particular kind of collection in which the principal (or only) operations on the collection are the addition of an entity to the collection (wikipedia).
In our case, the entity is an image or a spectrum. All entity have to be similar, so you cannot stack image and spectra together.
The easiest way to create a movie is : select all images at once ; click on "Images to Stack" ; start the animation. Options for the animation can be set up using "Animation Options".
The reverse process consists in : "Stop the animation" and "Stack to Images".
A podcast show those actions in the case of Exoplanet's detection using radial velocity method.
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Another option is to use Slice.... You select one image, and add slice. The number of slices in your image will appear in the Properties of the Image Usage ?...
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