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Autofib is a robotic fibre positioner at prime, feeding light to WYFFOS in GHRIL. The optical configuration of the telescope is FOLDED (BROKEN) CASS, in order to direct the light of the WYFFOS calibration unit via the nasmyth flat up to prime.

Vital information like recovery procedures can be found on the AF2 main index


TCS: Focus (depends where you are looking!):
The best focus both on the WYFFOS detector and on the TV fibre-view is 82.25 mm. However, due to aberrations intrinsic to the WHT (mostly spherical), the best focus in the outer parts (>=20 arc minutes off axis) of the field may be as high as 82.65 mm. Hence a compromise value of e.g. 82.45 mm can be used. Fiducial stars right at the edge of the 29 arcmin field will be elongated by as much as 3-4 arcsec!
On the mobile probe the best focus is at a position of about 83.20 mm. This may be important to know when acquiring faint sources with help of the uDAS TV.

new uDAS Autoguider:
The camera looks at the output end of the guide fibre bundles (also called "fiducial fibres").
The new Small Fibres unit has 10 fiducial bundles:

Centres of the Fiducial Fibres:
It has been found that the fibre positions and/or shapes on the TV change with time, perhaps they depend slightly on EL. Before acquiring a new field check and if necessary move the marks of all fibres, illuminating the fibres using
ICL> wcal 4 on.
The marks are then saved to the file /home/whtobs/af2.reg, see the Region-menu of the display tool DS9.

uDAS Autoguider commands and startup:
The camera can be used as a conventional science camera as far as uDAS is concerned:
DAS> run AG4 2 "acq of NGC1162"
DAS> finish AG4
The first command will save the image on /obsdata... (e.g. for measuring seeing using IRAF, the pixel scale was measures 2/1/2003 to be 0.125"/pixel), the second command will finish an active exposure.
uDAS Autoguider has some extra features, that allow it also to be used as a TV.

The script will start the SDSU Autoguider GUI, a DS9 display tool and the talker window providing information on the system. The GUI allows you to change the exposure time, define the guide box size, choose between guide modes or TV mode and provides you with important information as the S/N ratio.
To start guiding: Note that switch-box for autoguider has to be set to the corresponding UDAS AG (LEO or CETUS)!
Images are piped directly to the display tool.

new uDAS TV:
The camera looks at the output end of the mobile probe fibre bundle.
The FOV is approximately 20" by 30". The mobile probe is used for acquiring, especially standard stars on individual fibres and science fields if the telescope pointing isn't very good. With good pointing you may try to acquire science fields directly with the uDAS Autoguider.
On the mobile probe the best focus is at a position of about 83.20 mm.

The arrows indicate the direction a star moves on uDAS TV (mobile probe) when in XY handset mode.

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uDAS TV commands and startup:
This is the same as for the uDAS Autoguider. The TV is called AG2.

Atmospheric Dispersion Corrector:
Check the PF atmospheric dispersion compensator is in 'ADC Only mode' (top right of prime mimic on ICL). If in doubt type:

Other screens and consoles:

Preparation (first night after instrument change)

Rotator centre:
The MOUNT PA range is -163.37...193.63 degrees, thus 357 degrees total. Hitting the limit you can't simply unwrap, you have to wait a certain time until you got past the 3 unreachable degrees. This may take a while, depending were the object is on the sky; therefore watch carefully what the limits are, each time you move to a new source! Calibrate: Define aperture offset:
Using a multi-object instrument it is recommended to define the aperture 0 offset, such the field rotates around the instrument centre. The instrument centre is defined as centre of the mobile probe, thus AFVIEWS at 0,0.
Last Parameters

Gripper centre
Afview [0,0]
Telescope aperture
Telescope focus
AG2 window: [110:500,40:500]


- The nominal offset for the rotator is -0.24  (22-11-04)
- When the external temperature goes below 5 degrees, the robot has to be awake and sleep. This can be done when an exposure has finished to avoid possible light to the detector.


Acquisition (first with uDAS TV, then with uDAS Autoguider):
This assumes the sequence 'rot centre' -- 'calibrate' -- 'aperture offset' has been executed successfully. You must have a field setup (AFSETUP) ready, the telescope must track the field and the rotator must track the demanded sky PA of the field. Before you start to expose sleep the robot!

Standard Star:
Follow this to acquire a standard star on an AF2 science fibre, correcting for a possible offset between GRIPPER centre and MOBILE PROBE centre and also for a possible small displacement of the mobile-probe fibre at the AG CCD end. This assumes the sequence 'rot centre' -- 'calibrate' -- 'aperture offset' has been executed successfully. You must have a field setup (AFSETUP) ready and the rotator must track the demanded sky PA of the field.

Once the GRIPPER centre is defined the procedure is reduced to: The D-tour via a fiducial fibre is to determine the gripper centre as the fiducial fibres have the same optical centre as the science fibres; this way you cannot miss the standard star.

When you take an arc, remember to offset the telescope away from the object or close the primary mirror cover as otherwise you get the two signals superimposed.

Data Handling


Access park:
Move first to AZ 300, EL 15; Switch to ENG; Press AP2 on platform; Open gate; Press AP3 on platform


Some more info from old Autofib notes:

How to reset the micro in GHRIL:

On the AF2 mimic, there is a status of the network connection. If this is
showing 'micro off the network', reboot the AF2 VME crate in GHRIL by turning
the plug for the crate off and then on after 10 seconds. Also check that the
network connection is properly plugged into the front of the crate.
If the ICL is giving problems after this consider killing and restarting the
AF2 task.

Added 02/08/2001:
1. To eliminate WYFFOS warning messages from ICL command window
2. afsetup fails continuously
3. af2 drops off the UTILNET
4. afsetup fails to ftp files

1. ICL>kill wyffos
start another Decterm on the ICL VAX
in the new window type "lpvg" and log on as observer
following login, type 'ICL' and
>load wht_wyffos_dir:wyffos_define

2. >kill af2_setup
>kill af2

3. and 4. - reboot the af2 crate

-------- © 2004 Isaac Newton Group of Telescopes --------
Last Updated: 22 November 2004 Juan Carlos Guerra