PNS MANUAL: Filter Calibration
For each filter, and for each tilt at which it is used, it
is important to perform a filter characterisation. The bandpass
of the filter changes over the field, with temperature,
and with aging of the filter.
So the filter(s) should
be calibrated often, and always if the tilt is
This is done by using a tungsten lamp to determine the filter
bandpass, in conjunction with the arc lamp exposures, which indicate the
Where relevant (lamp, filter angle)
!! UPDATE THE PNS HEADER CREATER GUI !!
How to take calibration exposures
This is just an 800-second version of the usual procedure
to increase the S/N, especially in the places where filter cutoff
weakens the lines. Check that the images are not saturated.
Perform the following commands, in sequence:
- Issue AGCOMP command on A&G console
(this puts mirror in calibration position). This can be slow; proceed meanwhile.
- Enter CALIB on PNS console (this puts in mask and opens shutter).
Ignore the 1-second countdown.
- Once AGCOMP above has completed, on DAS console give arcslong
command. This starts 800-sec integrations on both arms. Then
follow the instructions the script gives, spiced with beeps:
- On A&G console do COMPLAMPS CUAR+CUNE to switch on lamps.
- After 800 seconds you are asked to do COMPLAMPS OFF to switch them off again.
- A little while later the readouts will start.
- COMPND 1 - put in neutral density filter to prevent saturation
- COMPLAMPS W -- count to 12 seconds, then:
- COMPLAMPS OFF
- COMPND 0.0
- AGMIRROR OUT
Profile of Filter B
measured with the PN.S in the centre of the field at two tilt angles
in July/September 2001.
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Last updated 16-04-2004
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