How the Sequence Selects Work

Sequencing ››
Parent Previous Next

This section is intended to clarify how Sequence Generator Pro selects work during sequence execution:


Parts of a Sequence


A sequence consists of three hierarchical components:


Selecting Work


Execution of a multi-target sequence can be straightforward if it remain static during data capture.  When you decide you want to alter the ordering of targets or events in real time, you might observe unexpected behavior if you are not familiar with the sequencing rules.


Basic Rules


The simplest multi-target sequence will function as follows:



This basic set of rules gets a bit more complex when you decide to alter the sequence in real-time.  Here are some rules that are good to understand:




Typical use cases:



Special use cases:



Example:  A sequence contains targets for Horsehead, M42 and the Rosette nebula (in that order).  You start the sequence and then realize you wanted to start with M42 first.  Unfortunately, the Horsehead target has already started and, as a result of this, it is "sticky".  This means that any attempt to simply re-order the targets (even if you pause and restart) will result in the Horsehead target running to completion.  In order to force M42 to run, you will want to abort the sequence, move M42 above Horsehead, un-check Horsehead (this will remove the "sticky"), restart the sequence and then finally re-check Horsehead so it will be picked up after M42 completes.  Of course, this is only an example to illustrate how to do this, if you haven't really gotten too far into a sequence, the best option would likely be to reset the sequence.



Example:  A sequence contains targets for Horsehead, M42 and the Rosette nebula (in that order).  Horsehead runs until completion and the sequence moves on to M42.  During acquisition of M42, you realize you want to capture some more frames for Horsehead.  You move to the Horsehead target add a few more frames, but the target is still marked as complete.  Under normal circumstances, you can't add more work to completed targets.  But... if you really want to force the sequence to consider the new work for this target, you will need to open the settings for Horsehead and check the "Clear completed status" option.  After clicking "OK", the target's icon will change from the completed check-mark icon to the pause icon.  After M42 completes, the sequence will actually go back to Horsehead and finish your new frames (any target options like "center on when target starts" are applicable in this case).



When the sequence begins capture of a target it will continue its execution until it is done.  That is to say that the sequencer will not select work between targets during execution.  If you are using an event rotation option in a sequence that has multiple targets, the sequence will not rotate through all events in the sequence, but rather rotate through all events in the target and then move to the next target.


The sequencer selects works in a hierarchical manner.  That is to say that it will always consider events on the target in the highest (top-most) position first.  If you have defined multiple targets, the sequence will start executing events from the "top-most" target and finish with events in the "bottom-most" target.  This logic will always remain true, even if you reorder the targets.  For example, if you have three targets and run half of the events in the top-most target, pause, move target 2 to the top-most position, target 2 will start up when the sequence is resumed and the next available event for target 2 will begin to run.  Targets can be re-ordered in real time and the same rules will apply (in this case the current event will always finish).  If you pause and resume the sequence in such a way that does not cause the current / next target to change (i.e. run pause / resume with no target reordering), then the sequence will resume where it left off (i.e. same target, next event).  


Targets and events that are not "checked" will not be considered for work.


Resetting the Sequence


There are several ways you can alter the state and progress of a sequence.  See here for more details.