Guider Issues

Tuesday, February 6, 2018 2:56 PM

Problem(s) Encountered:

The guide probe misbehaved a lot at the beginning of the night. We had to

restart it before even going on sky (we tested sending it to center and then

origin, and it got stuck). When we went on sky it *seemed* ok as far as the

workstation GUIs were concerned - JSkyCalc was reading the position and it went to origin and center consistently, but when trying to get a guide star it was horrifically off. Even if we sent the probe to center, lined up the telescope on a bright star, then moved to a guide star, the probe was off again. And we were at X<<10000. Eventually we restarted the MIS again and things were fine after that.


This will be dedicated to the guide probe issues as it is possible (likely even?) that the issues there were causing vignetting to a varying degree, resulting in reduced counts.

Pulled off OSMOS and the bottom plate of the MIS this morning and found a sticky 0-limit switch for the y-stage.  Within one cycle, it stuck closed completely and failed.  Replaced the limit and ran the stage to origin (0,0) and the new limit failed immediately.  I chalk that up to a bad limit switch.  Hit the “Stop” button on the xmis2 GUI (wonderful feature!!) when it started to scream as the y-stage was trying but could go no further.  Moved it back off its limit and replaced the switch with yet another.  Very carefully this time, I approached the limit and ran the stage in, verifying that the limit really was working before letting the system run to the limits.  All seemed well so I’ve been exercising the stage, sending it commands via x- y- demand values, as well as running preset commands for motion.  During this, while the x- & y- positions appear correct in both the xmis2 GUI and JSkyCalc, the status line on the bottom of the GUI, as well as the indicated values in the log file are curious.  See the image below.  I don’t know where it is getting these exponential numbers (i.e. x=2.208e+06 y=2.01e+06 [steps]) but they are obviously wildly off.  Still, as stated, the values elsewhere are correct, and watching the guide probe, it moves where I expect.  It is of note that these exponential numbers only occur when using the preset>center and preset>slit commands to move the stage.  If I enter the x- & y-values for, say the center position, it goes there correctly, and displays correctly (no exponentials).  Also noteworthy, preset>origin produces correct values (x=0 y=0) in the status line and log file.  Perhaps this is a longstanding bug in the code?

I will run more tests before buttoning everything back up, demanding movement via presets, x- & y-inputs, as well as from JSkyCalc, to make sure all continues to appear nominal.  But right now, it all looks like it’s fixed.

Once the MIS is back together and OSMOS back on the telescope, I’ll run some comp spectra and see if the counts are ballpark where I’d expect them as well.