Setting and Displaying Spectrograph Mechanisms

With few exceptions, the control commands for UCLES and UHRF are almost identical, although the effects on hardware may differ. In the command summary below, the prompt is given as : for commands that operate in either mode, or the instrument prompt is given for commands specific to UCLES or UHRF.

Configuring UCLES:
It is possible to demand any optical wavelength at the centre of the detector.

UCLES: CENTRE grating (Å) filename
... to compute the settings which centre wavelength on the detector, using the specified grating. The settings are output to the named control file. (Hint: Use as the filename too.) Use CENTRE PEAK to centre on the blaze peak of the order in which falls, rather than on itself.
UCLES: USE filename
Adopt the named control file.
UCLES: CONFIG SLAUTO
Configure the hardware using the control file specified by USE. The SLAUTO keyword selects the maximum slit length that maintains an interorder gap of 1 pixel:

Configuring UHRF:
UHRF cannot yet acquire any arbitrary wavelength at will. Either an existing control file must be used, or else a new file must be generated using previously determined settings. The instrument scientist will determine settings for new wavelengths given advance notice.

To access an existing control file:
UHRF: DIR
Directory of system control files.
UHRF: FETCH filename
Bring system control file into current directory.
To create a new control file:
UHRF: CENTRE
... create a new UHRF control file. Specify the EMPIRICAL option when prompted, and enter the values requested, in encoder units.
To configure UHRF with the control file:
UHRF: USE filename
Adopt the named control file.
UHRF: CONFIG
Configure the hardware using the control file specified by USE.

Displaying the spectrograph status:
Several commands are available to interrogate the spectrograph status:

: DISPLAY
Display spectrograph configuration. Check filters out of the beam for CCD, or sensible filters in the beam for IPCS. Items in motion are marked by *'s. Reverse video emphasizes anything in an unusual state. Use DISPLAY OUTPUT= filename to write the display to an ASCII file.
: R item
... to read a specific item, in default units e.g. R BR
: RU item units
... to read an item in specified units e.g. RU SW PIX

Mechanisms to configure interactively:
Not all spectrograph mechanisms are affected by the control file. Slit dimensions, use of the image slicer, beam rotator, or UCLES focal modifiers, and filter settings, calibration lamps, and TV mirror controls must all be set interactively.

: CANCEL action
halts action currently being modified.
: SLIT item
Select item = SLIT or SLICER.
: SW x units
... to set the slit width to x units, where units = MM, PIX, or ARCSEC.
: SL x units
... to set the slit length to x units, where units = MM, PIX, or ARCSEC, if not using SLAUTO.
: SF1 n
... to set Slit Filter wheel 1 to filter n. Similarly SF2 n, LF1 n, LF2 n for the other Slit and Lamp Filter wheels.
: ARC lamp
... where lamp is one of QUARTZ, THAR, or LASER to direct light from the specified calibration lamp onto the slit/slicer.
: LOF
... turn off lamp, but don't move optics.
: TV SLIT
= STAR ... turn off lamp, and remove calibration lamp optics. Return TV view to slit/slicer.
UCLES: TV WIDE
... change from slit view to 1 arcmin field.
UCLES: FM IN
... if Focal Modifier desired with UCLES, or FM OUT to remove it.
If the beam rotator is to be used with UCLES, there are several additional commands:
UCLES: VERTICAL
... insert beam rotator and maintain parallactic angle.
UCLES: CANCELVERTICAL
... halt rotator, but leave it in.
UCLES: TRACKPA pa
... insert beam rotator and maintain a particular position angle pa.
UCLES: CANCELPA
... halt rotator, but leave it in.
UCLES: BR OUT
... remove beam rotator from optical path.

Many mechanisms have a limited range of travel. MIN and MAX are valid values to set them to their limits, e.g. SL MIN to obtain the shortest possible slit length.