AF2+WYFFOS Essential Observing Guide

Two main computers are used by the visiting astronomer when observing with AF2+WYFFOS:

• taurus, a Sun workstation where the data acquisition system (UltraDAS) and AF2 control software are run. Mimic windows are available for the CCD, AF2, and WYFFOS status, and commands for all systems are typed in the WHTICS window (SYS>prompt) under Unix, which means that you can run commands in background and write scripts.

• whtdrpc1, a Linux PC where frames can be displayed and analysed using iraf. Note that if you plan to reduce your data on the fly please consider that you can't operate on the images stored in the /obsdata directory. You can create a directory in the /scratch filesystem (e.g. /scratch/whta/20040110) and copy the images there to proceed.

The telescope control system (TCS) computers are instead ran by the Observing Support Assistant (OSA).

The commands generally used by visiting astronomers are listed below.

All Wyffos commands are run from the taurus machine. They  can be executed via the WYFFOS Graphical User Interface (GUI), or typed as command lines in the WHTICS pink window (SYS> prompt).  There, you can type and execute the commands listed below, or include them in Unix scripts to automatically execute sequences of commands (SYS> source script_file). A complete manual can be found here.

SYS> command_name -h
provides help information about a specific command being printed on the console.

SYS> wcenwave xxxx y
sets central wavelength to xxxx angstrom for order y (the latter parameter to be entered only for the echelle mode).

SYS> wsetfocus xxxx
set instrument ("slit") focus to xxxx nm.

SYS> wslittran xxxx
sets "slit" translation to xxxx nm.

SYS> wfilter  A/B  in/out
puts filter A (or B)  in (or out) of the beam, and applies automatically the corresponding focus compensation.

SYS> wchange  -grating grating_name  -offset grating_offset_value  -order grating_order
changes one or more of the parameters used by Wyffos, like the grating_name, the grating_offset_value (default to 6.85 deg), or the grating_order.

SYS> wcallamp xx
switches on calibration lamp with Name xx (or at Position xx, see below). Currently available lamps are:

Type	Name	Position
Quartz-Halogen-Tungsten	QTH	1
Neon	Ne	2
Thorium-Argon	ThArCr	3
Helium	He	4

SYS> wlamptime xx
sets the timeout time xx (in seconds) for automatic switch off of lamps.

Alternatively, all WYFFOS commands can be executed by means of a GUI in the taurus machine. The GUI for the visiting astronomer appears as

All AF2 commands are run from the WHTICS Observing System window in taurus. They  consist of the string 'af2'  followed by a space, another string specifying the action, and in some cases also a list of parameters needed by the action. By typing

SYS> af2

the list of all AF2 commands is printed on the screen.

Copying fibre configuration files to the Observing System and check them

Before setting up a field, the corresponding configuration file (.cfg) should be copied into the Taurus machine. In Taurus, within account whtobs, enter subdirectory /home/whtobs/AF2, and copy there your .cfg file from any other ING machine
(subdirectories with your name within the AF2 directory can also be created).

SYS> af2 check name_of_file.cfg.x
allows  you to check the validity of your configuration file withouth performing physically the fibres setup.

SYS> af2 checkt name_of_file.cfg.x hh:mm:ss.s
the same as above, but allows different choices of the sidereal time hh:mm:ss.s

Setting up a field

SYS> af2 wake
switches the AF2 robot on

SYS> af2 setup name_of_file.cfg.x

sets the configuration contained in file named name_of_file.cfg.x. You will be asked for the SIDEREAL TIME  for the configuration; this provides the HOUR ANGLE used to transform sky coordinates into plate coordinates, overriding the value of the parameter "H.A." in the .cfg.x file. When the setup is in progress the process can be executed in the background by typing Ctrl Z and bg at the SYS> prompt. Never move the telescope whilst a setup is in progress.

Note that with the new AF2 software a complete setup usually takes less than 20 minutes.

SYS> af2 recover
If a fibre is lost during a setup, you can try to recover it by issuing this command. First, record the sequence with the video recorder, ensure the back-illumination is on, and inspect the failed fibre with the command 'af2 viewfibre nn', as well as the neighbouring fibres. If the fibre is recovered using 'af2 recover', you can restart the setup. If not, seek expert help from the OSA or SA; this situation most likely requires a physical inspection of the fibre module, and physical retrieval of the lost fibre. Specifically, do not repeat the 'af2 recover' command, and do not merely disable the problematic fibre in your configuration file and restart the setup. This risks damage to the fibres because the physical position of the problematic fibre is no longer known with certainty.

SYS> af2 sleep
switches the robot off. This is recommended after a setup is finished, and is mandatory if working in the far red, as near-IR inspection lights in the robot would cause scattered light to appear in frames.

Note that the fibres configuration can be done at any telescope position, as fibres do not move on the plate when telescope is moved. So, it is safe to set in the afternoon the first configuration field used at night. However, as the xy plate coordinate system might have a general drift with large telescope movements, if the same field has to be reconfigured during the night, we suggest to run the AF2 command

SYS> af2 loadmodule

Checks and updates the positions of all the usable fibres (i.e. not dead or disabled) in the fibre module.

(this takes 2 min) before reconfiguring the field. 

Other useful commands

SYS> af2 allcircle
puts all fibres in a circle

SYS> af2 allpark
parks all fibres

SYS> af2 park
parks robot out of field of view

The complete list of commands can be found in the UltraDAS dictionary. Some of the most important ones are listed below.

SYS> rspeed wyffos slow/fast
sets readout speed of the camera to slow/fast mode.

SYS> bin wyffos x y
bins camera pixels to x and y values

SYS> bias wyffos
takes one bias

SYS> multbias wyffos n
takes n biases

SYS> run wyffos xxx "title" &
runs (in background) a science exposure of xxx sec, and puts a title in the FITS header.

SYS> multrun wyffos nn xxx "title" &
starts nn science exposures each of xxx seconds.

SYS> abort wyffos
aborts current exposure. No image is saved on disk.

SYS> finish wyffos
stops immediately the current exposure, and the frame is saved on disk.

SYS> newtime wyffos xxx
changes the exposure time of the current exposure to xxx seconds.

The same syntax as for the "run" command is used for the flat (flat fields), arc (arc lamps), sky (sky offsets), with the only difference that the corresponding FITS header is filled with the exposure type.

Observing a science field

When a field is setup for the correct Sidereal Time, just give the coordinates of its centre, equinox, and the sky Position Angle to the OSA, who will acquire the field and start guiding. Exposures are defined using the UltraDas commands in the previous section.

Acquiring a standard star

This requires knowing the offset between the gripper centre (where the fibre is) and the mobile probe sky viewing camera. To do it, you must have a field configured.

Step 1: Determine gripper centre

This step is carried out on the AF2/WYFFOS setup night by the OSA, with input from the support astronomer. From time-to-time it may need to be redone during a run by the OSA. It assumes the sequence rot centre, calibrate, aperture offset has been executed successfully by the OSA.

Move the telescope to a relatively bright star:

SYS> af2 wake

SYS> af2 viewsky 0 0
and centre the star on the probe centre.

SYS> af2 offsettel SKYPA STARNAME FIDUCIALFIBRENR
where FIDUCIALFIBRENR is the number of a fiducial fibre inside the field (close to the centre of the FoV), SKYPA is the current sky position angle, and STARNAME in any string of characters. Answer the questions (first 'no' then 'yes'). This offsets the telescope to ideally put the fiducial fibre on the top of the star, and also moves the mobile probe to see the star.

SYS> af2 park
remove the mobile probe, and centre accurately the star on the fiducial bundle using acquisition camera.

SYS> af2 viewobject FIDUCIALFIBERNR
(same fiducial fibre number as above). See where the star ends up on the mobile probe sky viewing image, and mark its position with a cross. This cross reflects the gripper centre. When acquiring another field or standard, use this cross as the acquisition reference.

Step 2: Acquire standard star in a science fibre

This step is carried out each time you want to observe a standard star.

 Move the telescope to the standard star;

SYS> af2 offsettel SKYPA STARNAME SCIENCEFIBRENR
where SCIENCEFIBRENR is the science fibre where you want to obtain the standard spectrum, SKYPA is the current sky position angle, and STARNAME in any string of characters. Answer the questions (first 'no' then 'yes'). Ask the OSA to centre the star in the cross marked on the mobile probe camera.

SYS> af2 park (or af2 sleep)
Park (or sleep) the robot. Now you can proceed to take the exposures of the standard star.

You can either bring your data home in a USB external hard drive if you have one, or by burning it to a DVD. There are detailed instructions on how to do both here.