Date: Thu, 11 Dec 2003 11:46:51 -0700
From: Dan Long
Subject: Re: 2.5m obslog 20031210 (MJD 52984)
Jon,
    The numbers you quote at the end are for the mechanically
collimated position of the primary.  We have never achieved getting
the actual collimated position to be the same as the mechanically
collimated one (only possible if the secondary is perfectly centered
over the primary).
    The actual collimation numbers use the mechanical collimation as a
starting point. Coma is then removed using tilts.  A formula is then
used to convert the tilts to a combination of tilts and translation
which give a collimated position of the primary given the position of
the secondary.  Bottom line, the numbers are what they should be.
				Cheers,
				  Dan
>  >                        APACHE POINT OBSERVATORY SDSS 2.5M
>>
>>                                   OBSERVING LOG
>>                            Wednesday December 10, 2003
>>
>>                                    (MJD 52984)
>  ...
>>     I also completed the procedures of: Home Secondary and Home/Relax
>>  Primary.  I had no problems with M2, but the mig values (E and F) were
>>  high for M1.  I went through the Home/Relax process again and got the
>>  same high numbers.  See Mirror section.  I talked with Jon B. about the
>>  problem.
>  ...
>>  ---=== MIRROR NUMBERS ===---
>>
>>  PRIMARY:
>>  --------
>>  Scale: 1.000000
>>
>>  MIGS        TONIGHT   NOMINAL
>>  Axial A      0.5430   0.5450
>>  Axial B      0.6320   0.6370
>>  Axial C      1.0900   1.0850
>>  Trans D      -8.4530  -8.4550
>>  Lateral E    10.8966  10.7442
>>  Lateral F    10.8585  10.7823
>>
>>  GALILS
>>  Commanded: 4600. -2850. 850. -9250. 18400. 17850.
>>  Actual:    4600. -2850. 850. -9250. 18400. 17850.
>
>
>I took a look at the history of the Lateral E and F values and the
>commanded positions for them in the recent night logs.  I note that the
>nominal value was changed from:
>
>>  Lateral E             10.9093
>>  Lateral F             10.8712
>
>to the current values noted above in the log of Sunday, November 16,
>but no corresponding change in the Galil commanded positions were
>recorded.  The observing log for this day notes:
>
>>  We have a new set of nominal mig values due to the change in mechanical
>>  colimation.
>
>As expected, the actual values are running more or less near the old
>nominal values.
>
>French's day log of November 13th notes:
>
>>  these were achieved at the following actuator numbers:
>>
>>          A   =   4600
>>          B   =  -3200
>>          C   =   0
>>          D   =  -9800
>>          E&F =  -9300
>
>which should be the new Galil commanded positions.  It appears from the
>obs logs that we have not been using the new collimation positions.
>
>Jon
>
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