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WORKING WITH AUTOFIB/WYFFOS

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.

A new LINUX machine is setup to run the AF2 robot and a new GUI to display the AF2 status.

First Night Tasks, (determining Rotator Centre, Gripper Center)

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

Last Parameters

Gripper centre
(viewsky 0,0)

172,213

181,221

151,219

21/11/05

17/08/05

20/04/06
Rot. Center Af2
viewsky -600,500

viewsky 0,0

148,116

202,208
192,174

21/11/05

17/08/05
20/04/06

08/06/07
Telescope aperture '0'
 0.6,8.9
 21/11/05
Telescope focus
 82.50
 09/06/05
AG2 window: [160:550,30:500]
Nominal Rotator offset: -0.36 to -0.45  (20/04/06)

SOME LINUX COMMANDS:

TO>AF2  VIEWSKY 0 0
TO >AF2  WAKE
TO >AF2  SLEEP
TO >AF2  PARK
TO >AF2  RECOVER
TO >AF2  VIEWOBJECT 112
TO >AF2  MOVEFIBRE 16 0 0
TO >AF2  OFFSETTEL


.......more in the AUTOFIB web page


Startup
TELESCOPE SETUP -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.

The uDAS Autoguider:

General Information;

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:

  • Each consists of about 10,000 (yes!) individual fibres.
  • These make up a coherent bundle about 100 microns wide.
  • Each give a view of about 8 arcseconds on the sky.
  • The 10 bundles are arranged in a rough circle with numbers in this order:
    (clockwise from bottom) 144, 128, 112, 16, 32, 48, 64, 80, 96 with 160 in the middle.

 

The Autoguider commands and setup.

uDAS "Acquisition" 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 TV commands and setup.

Atmospheric Dispersion Corrector:
Check the PF atmospheric dispersion compensator is Enable. Looking the Instrument Control Console, the ADC update: ENABLE.

Other screens and consoles:

Acquisition Procedures

FIRST NIGHT.

Defining Rotator centre, Telesope Pointing and Gripper centre.
ROTATOR CENTRE
  • Move to a 12 mag.star.
  • Using the TV in continuos mode.
  • Set a window in the TV.
  • TO>AF2 VIEWSKY 0 0 (move the robot to the centre of the field.)
  • ROT SKY 0.
  • Measure the position x and y.
  • Rotate 180º, then measure again.
  • Calculate the rotator centre.
  • Mark the rotator centre to further references.
TELESCOPE POINTING.
  • Using the rotator centre position to perfomance a Telescope Pointing Calibration.
APPERTURE OFFSET
  • Pointing to 12 star magnitude.
  • AF2 VIEWSKY 0 0
  • Center the star using the HANDSET in mode APOF.
  • Store the position. USER>store ap 0.
GRIPPER CENTRE
  • Field configuration setup done.
  • Rotator in tracking with the demanded SKY PA.
  • Goto a faint star (or some standard).
  • Select a fiducial and offset the telescope to look the fiducial.
  • Look the star position using the TV.
  • TO>af2 offsettel SKYPA STARNAME FIDUCIALFIBERNUMBER (answear question; 'no' and then 'yes').
  • TO> af2 park. (to see the star in the TV).
  • TO>af2 viewobject FIDUCIALNUMBER (same fiducial as above).
  • See where the star ends up and mark the position as GRIPPER CENTRE.
  • Check using a science fiber.
  • TO>af2 offsettel SKYPA STARNAME SCIENCEFIBRENUMBER. (answear question; 'no' and then 'yes').

 

Acquiring a Configured Field using the Fiducial Fibres

  1. Observer must have run AF2 SETUP for the field being acquired.
  2. The astrometry (star position information) used by the observer to generate the configuration, must be accurate in order that several fiducial stars coincide with fiducial fibre positions AT THE SAME TIME.
  3. The telescope pointing must be reasonably accurate (Calibrate Sky r.m.s. <6 arcsec approx.). You can test the pointing on a bright pointing grid star by putting the "moving probe" (camera on the fibre positioning robot) in the center of the field using the command AF2 VIEWSKY 0 0. Moving this star onto the GRIPPER CENTER using handset will tell you the pointing correction. If the pointing star is close to the target field, you can apply this correction at the field position and the fiducial stars should fall into the fields of view of the fiducial fibre.
  4. Arotator offset must be applied. If the pointing is accurate (or the above correction is applied) then fiducial stars close to the centre of the field will show up in the field of view of the corresponding fibres. If there are no fiducial stars close to the centre then you may need to move the rotator a small amount (usually 0.2 to 0.5 degrees in the negative direction) using the HANDSET. Wait for 3 readouts of the acquisition camera to see the updated position. Adjust the rotator position and XY position to bring the fiducial stars as close to the fibre centres as possible.

If the above procedure fails to acquire fiducial stars, try the "long acquisition procedure", which uses the larger field of the moving probe to first get a fiducial star close to the correct position (the gripper center) and helps to find the rotator offset from scratch.

Acquisition (Long version, when pointing is not good enough to put fiducial stars directly in fibres):
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.


Acquiring Standard Star onto Science Fibre

Once the GRIPPER centre is defined the procedure is reduced to:

The detour 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.

Arcs:
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.

MISCELLANEOUS

Telescope @ acces park:

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

NEW LINUX INTERFACE GUI

 

How to reset the micro in GHRIL: (Obsolete - there is no Miro with the new linux system)

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.


-------- © 2007 Isaac Newton Group of Telescopes --------
Last Updated: 2007 Juan Carlos Guerra