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ACAM Acquisition Tool: Calibration Constants


This page is intended to keep a record of the calibration constants used by the ACAM acquisition tool. This will provide a reference point should the values be inadvertently changed in the database. In addition it will be possible to monitor any changes in the relative positioning of the telescope/instrument system.

Overlay
 Date
 Value
 Person
 Source/Comment
Plate Scale (arcsecs)
 17-11-2010 0.2535
 srix
 CRB measured a pixel scale of 0.253 and 0.243 in x/y, through R-band filter.
Camera Mount Error (degrees)
 17-11-2010 90.68
 srix The telescope is meant to be calibrated so that N lies along the slit (to the right).
Note that the slit is rotated 0.68 degrees clockwise with respect to the detector rows.

22-11-2010
 90.15
 srix
 Following the rotation of the detector (10/11/2010), the slit is now rotated 0.15 degrees clockwise with respect to the detector rows. (Note that the telescope and slit have not moved relative to each other.)
Slit Angle (degrees)
 17-11-2010 -0.68
 srix The slit is rotated 0.68 degrees clockwise with respect to the detector rows.

22-11-2010
 -0.15
 srix
 Following the rotation of the detector (10/11/2010), the slit is now rotated 0.15 degrees clockwise with respect to the detector rows.
Tweak Correction (degrees)
 17-11-2010 -0.68
 srix The telescope is meant to be calibrated to x movement corresponds to the slit orientation (not the detector row orientation). The slit is rotated 0.68 degrees clockwise with respect to the detector rows.

22-11-2010
 -0.15
 srix
 Following the rotation of the detector (10/11/2010), the slit is now rotated 0.15 degrees clockwise with respect to the detector rows.
Derotator Pixel X
 17-11-2010 1098
 srix Determined by CRB (10/2009).





Derotator Pixel Y
 17-11-2010 1890
 srix Determined by CRB (10/2009).





Slit Centre X
 17-11-2010 1033.5
 srix -

22-11-2010 1023.5
 srix
 Remeasured after the rotation of the detector on 10/11/2010. (The value was determined with the 1" slit, the SloGunR filter and the telescope at zenith.)
Slit Centre Y
 17-11-2010 1950.0
 srix Possibly measured for 1" slit with SloGunR (but not certain).

22-11-2010 1951.0
 srix
 Remeasured after the rotation of the detector on 10/11/2010. (The value was determined with the 1" slit, the SloGunR filter and the telescope at zenith.)

Note that the 'Slit Centre Y' will vary with telescope position, slit and filter. Therefore its value is constantly updated by the user. Nevertheless it is useful to have a record of the value with a standard setup to monitor stability. For now it is recommended to use the 1" slit, with the SloGunR filter, and the telescope positioned at zenith.

When the calibration parameters were redetermined after the detector rotation (see updates on 22-11-2010), they were also checked with the clear position. This caused the 'Slit Centre X' to shift from 1023.5 to 1027.5 and the 'Slit Centre Y' to shift from 1951.0 to 1946.9.

Instrument changes:

1) On 20101110 the ACAM CCD was rotated so that the arc lines would be better aligned with the detector rows. Previously Chris had measured a rotation of the arc lines of 0.67 degrees over the central 2.5 arcmin, with the lines sloping from top left to bottom right. Post-rotation and post-tightening, Chris reported a rotation of 0.25 pixels in the central 400 pixels, ie. 0.04 degrees. (Presumably this was also referring to the arc lines.)

In imaging mode, the slit was originally rotated 0.68 degrees clockwise with respect to the detector rows. After the change the rotation was reduced to 0.15 degrees (clockwise).

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Last modified: 25 October 2013
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