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focusz stsdas.hst_calib.hrs.z_calib



focusz -- Estimate GHRS detector focus.


focusz input table newtable


The GHRS focus parameter is computed using observations of either the left or the right photocathode edge--all observations are taken at the same Y-deflection.

First, the data is merged into a single substepped image. The X-position of the 10% and 90% level of the edge is then determined. Finally, the focus parameter (in deflection steps) is computed as the difference of the 10% and 90% level positions.


input [file name template]
File names for the input observation data. All observations must be for the same detector and Y-deflection. They must be observations of either the left or right photocathode edge.
table = "focusz" [file name]
Name of the output focus table created by focusz. This table will have the following columns:

     'DETECTOR' - Detector number (integer).
     'EDGE'     - Edge observed (right or left) (char*5).
     'HV'       - Photocathode high voltage (real).
     'TWEAK'    - Tweak coil current (real).
     'YDEF'     - Y-deflection (real).
     'FOCUS'    - Focus parameter in deflection units (real).

newtable = "yes" [boolean]
Create a new table for the output from the output of this task?

If newtable is set to "yes" then a new table is created, otherwise, the results will be appended to an existing table.


1. Compute the focus using the observation image edge1 and create a table for the output called ftabout.

hr> focusz edge1.hhh[*] ftabout yes

2. Compute the focus using the input image edge2 and append the results to table ftabout, which was created in the previous example.

hr> focusz edge2.hhh[*] ftabout no


This task was modified to no longer search for the TWEAK (tweak coil current) keyword in the header of the input files. This keyword was not utilized by the task and only written to the output focus table. The modification was necessary as the TWEAK keyword is not present in the input headers.




For assistance using this or any other tasks, please contact or call the help desk at 410-338-1082.


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