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Old 13-09-2014, 08:15 PM
AndrewJ
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AndrewJ is offline
 
Join Date: Mar 2006
Location: Melbourne
Posts: 1,905
Gday Andrew

Quote:
I'd expect if the max duration was insufficient that once guiding stabilised the corrections would always be in the same direction and the plot would drift off the top or bottom of the graph.
Dont understand here, why would it drift off the graph????
The plot came from a mount that uses belt drives all the way to the final axis. It has very large but very smooth PE.
When the PE "rate" was small, it guided OK, but when the PE "rate" was changing at its maximum level, it couldn't keep up, hence the star drifted, but was still "locked" onto. ie PHD2 still knew it needed to bring it back.
On the PE "rate" slowing down then reversing, the guiding managed to incrementally catch up and the plot came back to centre and guiding once again worked for a while, then cr@pped out again later.

ie PHD2 can set a max "pulse time". This creates an absolute limit on how much error can be accounted for "timewise" in a given frame.
The scopes guide rate and PHDs aggressiveness, hysteresis and all the you beaut algorithms etc are all irrelevant if at the end of the day, they calculate a pulse time required that is greater than is allowed by the max pulse time.
I fully agree PHD2 should provide a warning if the max pulse time is hit for more than say 2 consecutive guides.

Andrew
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