Pre--observing Checks

Focussing UCLES
The depth of focus for UCLES is substantial and it will be rare that focus changes are required, but it should nevertheless be checked.
Configure spectrograph to wavelength of interest.
CCD: use a narrow unbinned window ( e.g. TEK1K_SETUP or THOMSON_SETUP)
IPCS: use ND filters over the arc lamps ( i.e. LF1 8 and LF2 3) and gradually remove them until the maximum countrate is below 1 Hz. Because of the large IPCS window used with UCLES the countrate limitations are severe and it is advised that the countrate should not exceed 0.5 Hz in any of the measured lines.

UCLES: PIXELS
... verify that UCLES knows the pixel size.
UCLES: CONFIG SLAUTO
... configure spectrograph
UCLES: SW 2 PIX
... use narrow slit with UCLES
UCLES: ARC THAR
... select arc lamp
UCLES: CF MIN
... set collimator
UCLES: HP DOWN
... set Hartmann mask, take exposure.
UCLES: HP UP
... flip Hartmann mask; take exposure.
UCLES: CF MAX
... move collimator
UCLES: HP UP
... take exposure with Hartmann up.
UCLES: HP DOWN
... flip Hartmann mask; take exposure.
Run the FIGARO routine FOCUS to compute a new collimator focus value.
UCLES: CF x
... Set recommended focus...
UCLES: HP OPEN
... remove Hartmann masks...
UCLES: SW 1 PIX
... set narrow slit...
... and take exposure of arc. YSTRACT a spectrum, and run EMLT to see the FWHM. For UCLES this should be about 1.7 Tek pixels.

Focussing UHRF
First focus on the red laser line at 6328.160 Å and inspect the instrumental profile. It should have a Gaussian FWHM of approximately 48 m, plus a low asymmetric tail to higher wavelengths. Tests with a green laser yielded the same value. Note that UHRF resolves the ThAr lines, so these cannot be used to assess the instrumental profile, but they are used to refocus UHRF for each wavelength setting, which is essential.
Configure spectrograph to wavelength of interest.
CCD: use a narrow binned window ( e.g. UHRF_X4)
IPCS: use ND filters over the arc lamps ( i.e. LF1 8 and LF2 3) and gradually remove them until the maximum countrate is below 1 Hz.

UHRF: CONFIG
... configure to laser or target wavelength. size.
UHRF: ARC LASER
... or ARC THAR for other wavelengths.
UHRF: R UFF
... check collimator setting
UHRF: HP DOWN
... set Hartmann mask UHU=UHL=0, take exposure.
UHRF: HP UP
... flip Hartmann mask UHU=UHL=1; take exposure.
There are two ways to proceed. Either move the collimator a random amount, take a second pair of Hartmann images, and then run the FIGARO FOCUS program, or run the routine FOC described in Section to help estimate a new collimator value. In the latter case, for every +1 pixel shift resulting from the cross correlation SCROSS hp_down hp_up, move UFC/UFF by -50 ADU at R = 1.0M, -80 ADU at R = 0.6M, and -170 ADU at R = 0.3M.
Recall from Section that UFC and UFF read the same encoder, but differ in their positioning accuracy, so UFF must be used for setting within 50 ADUs. Moreover, UFF will position poorly for motions less than about 20 ADUs, so should be driven away by 50 ADUs and back again if necessary.
UHRF: UFC x
move collimator
UHRF: UFF x
fine tune collimator if necessary
UHRF: R UFF
... check collimator setting
UHRF: HP UP
... take exposure with Hartmann up.
UHRF: HP DOWN
... flip Hartmann mask; take exposure.
Either run the FIGARO FOCUS program or run the routine FOC to help estimate a new collimator value. Once this process has converged, ...
UHRF: HP OPEN
... remove Hartmann masks.
If at the laser wavelength, take exposure, YSTRACT a spectrum, and run EMLT to see the FWHM. For UHRF this should be about 50 m, = 2 Tek pixels or 2.6 Thomson pixels.

Note that the HP UP configuration produces brighter spectra than the HP DOWN configuration.

The geometric structure of the image slicer modulates the signal in the spatial direction. This is clearly visible in the UHRF laser, ThAr, and quartz lamp exposures (see Figs and ). Observers may find it useful to take flat field exposures not only through the image slicer but also through the slit, using the maximum slit length ( SL MAX). These will provide more uniform illumination in the spatial direction which makes it easier to identify pixel--to--pixel variations. (Reminder: SLIT SLIT and SLIT SLICER swap between the image slicer and slit assembly.)

  
Figure: UHRF, 10 sec ThAr lamp @ 6328 Å, SLICER, UHRF_X4, XMEM orientation.

  
Figure: UHRF, 10 sec quartz lamp, SLICER, UHRF_X4, XMEM orientation.

Wavelength placement:
Even after doing a CONFIG, further adjustment of the spectrum positioning may be desired, especially with UHRF for which the spectrum coverage is so small, or for UCLES if partial orders are being recorded at one or both sides of the detector, in which case it might be desirable to shift the spectrum in the cross-dispersion direction to obtain a better coverage of one of these. With UHRF, observers may wish to force the VAX to use encoder units, rather than transformed units ( e.g. mm), by specifying RAW. To return to transformed units, specify REAL.

The most likely parameters to change are:

UCLES: EG eg
... adjust UCLES cross dispersion position, ECH_GAMMA, in degrees. Increasing ECH_GAMMA moves bluer wavelengths onto the detector. 1 unit (degree) corresponds to 24 mm on the detector. The same scale applies for ECH_THETA = ET.
UHRF: RAW
Force use of encoder units.
UHRF: UG ug
... adjust UHRF cross dispersion position, in raw (encoder) units.

UHRF: UT ut
... adjust UHRF echelle dispersion setting, in raw (encoder) units.

Once satisfactory grating and focus settings are obtained, they can be locked into the control files with

: ISET itemname value
... where itemname is the full (not abbreviated) form of the parameter being set.
: LIST
... to list the contents of the current control file. LISTed items can be ISET.

Other useful commands:

: PIXELS
... declare pixel size if CCD binning or IPCS pixel size changed.

: DCL dclcommand
... to execute a DCL command.

: O
= SS OPEN; slit shutter open (not with CCDs)
: K
= SS SHUT; slit shutter shut (not with CCDs)

: SHUTDOWN
... performs orderly shutdown of lamps, power supplies, kills all UCLES tasks, and exits from ICL. Not usually necessary during a run.

: EXIT
... leave UCLES software
: HELP
... accesses the online UCLES HELP library.