Sequence

The sequence node contains the iterator and observe commands that define the series of actions to collect data. It is possible to construct complex sequences using the iterators (and assumed in the following discussion that you have absorbed details of the individual iterators).

Sequence iterators can be nested, much like nested loops in a programming language. For each step of the top level iterator, the nested iterator cycles through all of its values. To illustrate this concept consider the following sequence containing an offset iterator and an observe (recall that the offset iterator defines a series of one or more telescope offset positions and the observe element takes data). The sequence folder contents are shown in figure (a) and the specific offsets, a 20 arc sec Dice 5 pattern shown in figure (b). In figure (c) we see the sequence details.

 

 

 

Note that the effect of reversing the order of the iterators is to create a sequence that cycles through the filters at each offset position: