Changes between Version 3 and Version 4 of HetProcedures/RA/iq

Timestamp:

Oct 7, 2022 10:10:21 PM (20 months ago)

Author:

stevenj

Comment:

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HetProcedures/RA/iq

@@ -29 +29 @@
 {{{
 lohobliq, in a perfect world, would be identical to the guider output, but it rarely does for many reasons. That is, however, not the main purpose. 
+
 This quantity, in conjunction with hobliq, will tell you how much low order component contributes to the image quality, which comes from mirror array global shape variation (not necessarily segment-to-segment variation). 
+
 In a way, this is similar to using guider output against seeing_mean, but it specifically calls out this smooth variation and I would include and use this differential as a secondary guide. 
 hobliq, in conjuction with seeing_mean, can tell you how much inter-segment contribution to the image quality there is, e.g. stack/piston.
+
 Typically, when image quality blows up, the differential between these terms starts to grow. 
 Often time, the difference between lohobliq and hobliq grows much faster, which I interpret as a sign of the mirror structure deforming.
-As such, it may give you an early warning to be prepared for a restack within the next 10~15 min. 
-Usually, the rate of change in difference between hobliq and seeing_mean is slower so this may not be the quantity you need to follow closely. 
+
+As such, it may give you an early warning to be prepared for a restack within the next 10~15 min. Usually, the rate of change in difference between hobliq and seeing_mean is slower so this may not be the quantity you need to follow closely. 
 
 I am hoping that incorporating the rate of change in those differentials might help you to better prepare for a restack a bit ahead of time. 
 
 Also, I would recommend you consider the expected improvement after a restack as part of restack preparation. 
+
 Often times, a re-stack occurred, but it did not improve the situation. This usually happens when the bottom-line image quality is already high.
+
 Sometimes, the overall image quality is so bad compared to a (also bad) bottom-line, a re-stack improvement is noticeable, but other times, it isn't. 
+
 This, of course, needs to be guided by the information about the constraints in a particular observing program.
+
 But considering what you expect to get after a restack will be useful in deciding whether to restack. 
-
-
 }}}