Obtaining the Calibration Data with TRISPEC

The page below describes how to obtain the wavelength calibaration data, and the flat flame with TRISPEC. Please note that the details given below are subject to change at any time.

How to obtain the wavelength calibration data

The wavelength calibration data is obtained by illuminating the instrument with the mercury-argon lamp (Hg-Ar lamp). Since the intensities of the emission lines vary largely as time passes after power on, it is recommended  to take a few frames with different passing times. To obtain the arc image, do the following procedure.
  1. Type "wcu in" on demi or on trispec. The arc lamp will be inserted on the front of the window.
  2. For obtaining the "off" image, take the image using the read.pl command.
  3. Type "wcu on" on demi or on trispec. The arc lamp will be powered on.
  4. After waiting for a few ten seconds, take a few set of the image.
  5. Type "wcu off" on demi or on trispec. The arc lamp will be powered off.
  6. Type "wcu out" on demi or on trispec. The arc lamp will be romoved on the front of the window.
For doing the above procedure, it is helpful to use the "arc.sh" script. This script will take the "off" image, and the arc images at the 30 and 90 seconds after power the lamp on, automatically. For example,
% arc.sh 0.302 4 5 hg_ar_0
will create the three sets for three channels, with the prefix "hg_ar_0_0" (for "off" image), "hg_ar_0_1" (for the 30 seconds after lamp on), and "hg_ar_0_2" (for the 90 seconds after lamp on), respectively. The following figures show typical arc spectra images on the spectropolarimetry mode. Please note that the wavelength increases from left to right in the optical channel, in reverse, the wavelength decrease from left to right in the infrared channels.
Optical Channel
(0.46um ---> 0.90um)
IR1 Channel
(1.80um <--- 0.90um)
IR2 Channel
(2.50um <--- 1.90um)

How to obtain the flat frame

For only the near-infrared imaging, you are able to use blank sky images at a number of spatial offsets as a flatfield. However, since on optical the brightness of night sky is no enough to make flatfield, you should also take twilight sky images before the beginnig of the night, or after the ending of the night.

For the spectroscopic modes, dome flats are obtained by the illuminating the dome with a lamp. At UKIRT, the TSS will prepare the Tungsten-Halogen lamp for dome flats. For obtaining good flat field data, a number of exposures with the lamp on anf off are should be taken with same paramters (slit, filters, grisms, number of sample).

For polarimetry, flat frame with each angle of the retarder should be taken.

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Last Modification Date: 2001/02/20
Last Modification Author: Makoto Watanabe <watanabe@z.phys.nagoya-u.ac.jp>