AF2 is a robotic fibre positioner at prime, feeding light to WYFFOS in GHRIL. In order to direct the light of the WYFFOS calibration unit via the nasmyth flat up to prime the optical configuration of the telescope is BROKEN CASS.

A new LINUX machine is setup to run the AF2 robot and a new GUI to display the AF2 status. The speed of setting configurations has improved.

First night tasks, (e.g. determining Rotator Centre, Gripper Center) and acquiring standard stars HERE

A new acquisition tool for AF2 has been written by Richard Bassom and is undergoing commissioning during semmester 2013A. See below for a brief description of how to use the new tool. Full draft documentation can be found HERE

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

• Set an APERTURE 0 to force rotation around the instrument centre.
• Different telescope focus on acquisition TV (83.2mm) than when observing with science or fiducial fibres (82.45mm)
• Robot movement commands which may not be remembered by observer (viewsky, viewobject, viewfibre, offsettel)
• Need to check fibre positions on CCD using WCAL 4 ON upon new target aquisition
• When dome temperature is cold (< 5 C), need to exercise the gripper regularly

LINUX COMMANDS for AF2 Robot:

TCS:

• USER> STATION PRIME
• USER> INSTRUMENT AUTOFIB
• USER> AGSELECT AF2_TV
• USER> FOCUS 82.45

Focus (depends where you are looking!):

The best focus both on the WYFFOS detector and on the fiducial fibre TV is 82.25 mm. However, to compensate off-axis aberrations, 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 is generally 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. Throughput or sensitivity of this camera is poorer than on AG5 (whtdas18)

The uDAS Autoguider (e.g. whtdas18):

This camera looks at the output end of the 10 fiducial fibre bundles
The AG camera and DAS machine numbers can be found on DEWARS
Each indiviual bundle has 10 smaller fibres which carry a proper image of the star to the camera:

• 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 top) 144, 128, 96, 64, 16, 80, 160, 32, with 112 and 48 in the middle.
• To make the star move in conventional cursor-arrow directions by setting the
  following in DS9: Invert Y and 0 deg

Centres of the Fiducial Fibres:

It has been found that the fibre positions and/or shapes on the AG camera 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:

• SYS> wcallamp He (W, Ne or Hg are other options)

The regions are then saved to the file /home/whtobs/AF2/OldReg/af2_yyyymmdd.reg, using Region/Save in DS9.

uDAS Autoguider commands and startup:

• On the DAS machine, log in as 'whtobs'
• Type 'obssys' then 'startobssys' in the yellow window
• Then type 'startag AGX' where X is the number of the camera being used
• To shutdown the AG system use 'shutdownag AGX' where X is the same as above

To start guiding:

• Set integration time and guide box size
• Select 'Select brightest star' or 'Manual select guide star' in SDSU AG window
• Click 'Guide'
• It may be necessary to enter 'AUTOGUIDE ON' (F9) on the TCS

Note that switch-box for autoguider has to be set to the corresponding autoguider!

uDAS "Acquisition" TV (e.g. whtdas17):
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 isnt 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 83.20mm.

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

       +------+
       |      |
       | <--- |
       |      |
       |      |
+------+------+------+
|      |      |      |
|  ^   | ---> |   |  |
|  |   |      |   v  |
|      |      |      |
+------+------+------+

To get the same directions as the conventional arrows, set the following in DS9: ROTATE 90 and INVERT X

uDAS TV commands and startup:
This is the same as for the uDAS Autoguider. The TV is called AG2 (see DEWARS for the DAS machine number).

• On the DAS machine, log in as 'whtobs'
• Type 'obssys' then 'startobssys' in the yellow window
• Then type 'startag AGX' where X is the number of the camera being used
• Windows can be set up using the usual uDAS syntax. The suggested AG2 window to view the mobile probe fibre only is as follows:
  SYS> window AG2 1 "[155:515, 25:490]" (21/02/13)
• Display the region file /home/whtobs/AF2/OldReg/af2_ag2_yyyymmdd.reg, marking the mobile probe, rotator centre (RC) and the gripper centre (GC)

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

• SYS> PF_MODE ADC_ONLY
• SYS> ADC_AUTO ENABLE

Other screens and consoles:

• The AF2 TV screen (little monitor above VCR) is used to view the back illuminated fibres when a new field is set up. You see the white spots defocussing as the robot picks the fibre up.

The new fiberguider software was written to enable more accruate and repeatable acquisition with AF2 and WYFFOS. It calculates the required XY translational shift and rotation to best centre all stars in the fiducial fibres. Commissioning of the tool is ongoing thoughout semmester 2013A. A brief outline of how to use the tool is given below:

• The acquisition tool is started using
  DAS> fibreguider &
  at the fiducial TV DAS prompt
• Once the 'Fibre Acquisition & Guiding' window appears, click 'Acquire' to open the 'Acquisition' window
• Acquire the observers field roughly as normal in TV mode, making sure to get 3 or more fiducial stars visible on their fibres
• Then stop the TV and click 'Field' in the 'Fibre Acquisition & Guiding' window. This will get the centres of all the fiducial stars visible
• Click 'Calculate' to determine the required shift in XY and rotation
• Then with the three checkboxes (apply XY, rotation and use TCS guide) ticked in the 'Acquire' window, click 'Apply'. This will first send the rotation to the mount as a TWEAK, then start the autoguider guiding on the arbitrary position 250 250. You should see these commands arrive at the TCS. During first nights commissioning the autoguider disabled itself automatically shorly after 'Apply' enabling it. Therefore, we then clicked 'Guide' in the 'Fibre Acquisition & Guiding' window to kick start the guider and make it pull the acquisition in.
• The required XY and rotation offsets are displayed in real time in the 'Acquisition' window, if they are still large (>0.01 degrees for rotation or > 0.5 arcsec for X and/or Y) after several iterations of the guider try repeating the above process of: 'field', 'calculate', 'apply' and 'guide' again to get rid of any residual error in the acquisition.

To calculate when a rotator limit will be hit

The Mount PA has a range of -163.37 to 193.63, so there is a blind spot of 3 degrees. It is useful to be able to determine the time at which a rotator limit would be reached for a new field, without having to move the telescope and read the information off the TCS. This can help to plan the observations during the night.

• Use Staralt to plot the Sky PA during the night for the proposed field
• If the parallactic angle is increasing throughout the observations, the rotator will be moving towards a negative limit
• If the parallactic angle is decreasing throughout the observations, the rotator will be moving towards a positive limit
• Use the formula:
  
  Parallactic Angle = Sky PA - Mount PA
  
  
• Given the Sky PA of the observations, and the Mount PA of either the positive or negative limit, obtain the parallactic angle for the time at which the rotator limit will be reached
• Use the staralt plot to read off the time for this parallactic angle

To determine if a rotator limit will be hit for fixed time observations

For a planned observation with fixed Sky PA and for a definite start and end time, we can determine in advance if a rotator limit will be reached during the observations:

• Use Staralt to plot the Sky PA during the night
• Read off the parallactic angle for the start and end of observations
• Use the formula:
  
  Mount PA = Sky PA - Parallactic Angle
  
  
• Make 2 calculations, one using the parallactic angle at the start of observations, and one at the end
• Obtain the Mount PA for both these times: if it falls within the permitted rotator range then no limit will be reached

Acquiring a configured field using the fiducial fibres

• The fibres must be in the correct positions! i.e. the Observer must have run AF2 SETUP for the field being acquired.
• 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.
• he telescope pointing must be reasonably accurate (Calibrate Sky RMS <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.
• A rotator 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 0.1-0.2 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 mobile probe to first get a fiducial star close to the correct position (the gripper center) and helps to find the rotator offset from scratch.

Acquiring standard star onto science fibre

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

• SYS> af2 offsettel SKYPA STARNAME SCIENCEFIBRENR
Answer the questions (first 'yes' then 'yes')
• Centre the star (TV) on what you now know is the GRIPPER centre
• SYS> af2 park (or af2 sleep)

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.

Access 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