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Swope Telescope operation manual

This manual describes how to take direct imaging CCD data on the Las Campanas 40-inch Swope telescope with the 4Kx4K E2V CCD231-84 detector. Last updated: November 9, 2017 (Nidia)

Activate telescope and instrument:

 

IMG_1124.jpg
Figure 1. Telescope Console
 
  • Turn on console (rotate key).

  • Turn power on.

  • Check that platform is down (red light on lightblue rack turns on when not).

  • On TCS display enter COVER (the telescope will move to the COVER position).

  • Turn the dome lights on from LPLC (see below).

  • Go upstairs, raise the platform with the hand paddle, and remove the telescope cover. Move the platform all the way down before going back to the control room downstairs.

  • On TCS computer type ZENITH and answer yes to the question about the platform being down.

  • Check that the TCS UT is right (compare with http://tycho.usno.navy.mil/what.html or similar). If not, fix it by entering the UT HH MM SS command.

  • Turn the dome lights off from LPLC panel.

 

The TCS and the guiders computers share the same monitor and keyboard.You can switch between them using the belkin KVM on the lightblue rack.

 

We recommend taking sky flats at twilight, which provide better correction (to 1% level) than domeflats. However, domeflats are useful for shutter and linearity tests. The domeflat position is reached by moving the telescope to HA=03:07E and DEC=-25:00 and the dome to encoder reading 282 (type DOME 282 on TCS). The quartz lamp is turned on from a box on top of the lightblue rack (do not exceed 935 Volts).

ff_box.jpg
Figure 2. Flat field lamp and Focus encoder
 
  • Turn on the fans from the switch in the next room.

  • The dome shutter is controlled from the Local PLC panel. Preferably open the done  with the telescope not pointing to Zenith.                                                                       .

    LPLC panel
Figure 3: LPLC panel 

 

  • The LPLC panel also allows control of  the dome lights and wind screen. A member of the day crew will show you how to operate it.
  • Start tracking by pushing ASCENCION RECTA on console.

  • Lower the wind screen. This can be done either from the LPLC or from the switch in the silver box next to the left side of the pillar.

  • To have the dome follow the telescope enter DOME AUTO on TCS.

  • The pointing model has to be active: the TP indicator should show up in green; if this is not the case, enter TP on the TCS.

Swope GUI

The SWOPE-CCD application consists of different controls:

1) Science Camera and Filter wheel control

2) Guiders control

3) Telescope control

In addition to these GUIs there are the image viewer (Quick look tool), the dewar status window, the airmass display and the object list window. A password protect mode allows access to the engineering GUIs.A detailed description of the application can be found here: http://instrumentation.obs.carnegiescience.edu/Software/Swope/

The detector is read out through 4 amplifiers producing four independent files called ccdnnnnc1.fits - ccdnnnnc4.fits. The quadrants as seen in the Quick-Look tool are named counterclockwise beginning from the top right quarter of the image (i.e., top right is c1, top left is c2, bottom left is c3 and bottom right is c4).

Science Camera and Filter wheel control

This window controls the CCD camera and the filter wheel. Exposures are started with the Start button. Macros can be started with the Execute button.

camera.png
Figure 4. CCD main window
 

Exposure parameters

ExpTime is the exposure time in seconds for the next observation. For this parameter and the ones for Loops and File# the entry window will be highlighted red after the number is typed. The value is not recorded by the program until the user hits Enter. The exposure time can be changed at any time during the exposure. Remember to hit Enter to validate the new value.

Loops: Setting up a loop can be a convenient way to take flat fields and bias, or to make a series of observations in order to split the total exposure into shorter individual ones.

ExpType: The exposure type (saved in the fits header) can be set to "Object", "Focus", "Bias", "Dark", or "Flat". Selecting "Bias" will automaticaly set the exposure time to 0 seconds. Selecting "Dark" will disable the shutter for the exposure. Selecting "Focus" will enable a focus sequence, automatically setting the loop number to 7 (this can be changed if desired). The focus frame will be saved under a normal filename (e.g. ccd0065.fits). In this frame, the spacing between the first and second images will be larger than for the rest of the sequence, allowing identification of the sequence order.

Binning can be set to 1, 2, 3 or 4 in rows and columns. Note that the readout time given in this manual is for 1 x 1 binning.

Filter: There is room for 10 different filters in the filter wheel. Clicking on the button will present you with the available filters. A 'combo' option is also available to allow combination of two filters.

One or more Quadrants can be selected to be read instead of the whole detector (note that this will not save time because each quadrant is read independently). The selection is enabled by clicking the Q checkboxes

Object: Enter here the title you want for the image.

File: File number will be automatically incremented for every new exposure.

Execute: This command is used to start a macro. The macro file name must be specified on the next window to the right. This option is useful when shutter time and/or linearity tests are performed. More details here:http://instrumentation.obs.carnegiescience.edu/Software/Swope/swopegui.html

Speed: only the Turbo readout speed is available at the present time.

Shutter: This is a flag that indicates whether the shutter is open or closed.

Snap will make a 4x4 binned image of the current field without incrementing the file number. The exposure time is as selected in ExpTime.

Subraster Allow to select subrasters on the chip. The regions can be defined giving its central coordinates followed by the width and height of the subraster (XYWH) or by its corners (XXYY). Savemode minimal will save only the selected region while savemode full will keep the original dimension of the quadrant filling with zero the region outside the selected.

 

subraster.png

 

Figure 5. Subraster Window
 

Pointing and focus

To point the telescope enter the following command on the TCS computer:

RA hh mm ss.s

DEC dd mm ss.s

SLEW

Panic command:

<Esc>   Immediately abort any dome or telescope move

<F1>    Display help screen

To check pointing, move the telescope to a bright star close to Zenith.

There is a list available on puma (object lists -→ cset.objects). Make sure that the equinox is right on TCS (MP 2000). Take a short exposure (1-2 s) of the field and compute the required offsets to place the bright star at the center of the image (scale 0.435 "/pixel). The telescope can be offseted from the TeleGUI. Take a new exposure and repeat procedure until pointing is right. Then type CSET on the TCS window and write down the ROFF and DOFF values, which will have to be entered manually if the TCS programm needs to be restarted for some reason. Next click on Centerfield on the guider window and check that the bright star ends near the center of the guider display. If it doesn’t, move the guider to place it near the center and then click on SetCenter on the guider window.

Focus sequences are allowed by setting Focus as ExpType on the CCD command window. This will allow 7 position sequences (Loops =7). This default can be changed to other number if desired. We recommend taking 10s exposures changing focus by 0.050 units in between. The secondary mirror is moved from a switch on the small silver box labeled focus which is on puma desktop. The focus needs to be determined for each filter to be used; focus readings around 24.000 will be obtained for most filters. Focus will change along the night depending on temperature and telescope position. Sometimes a new focus sequence will be needed.

Guiding

The main components of the guiding interface are the Skymap,Guider1 and Guider2 windows.

Skymap displays a star catalog and and overlay of the science camera field of view (red box) the patrol area of the guiders (blue boxes) and the area where the guiders vignette the science array (dashed rectangle). By selecting a star the catalog entry will be displayed in the text box in the lower left of the window. The selection will also update the probe relative position on the Guider window. The probe will be moved to that position by pressing the Goto button. The guider probe can be also moved by selecting an offset or by using the keypad (after selecting Enabled in the box next to it). The last section of the Guider window allows to select imaging mode (i.e. the guiding mode) or Shack-Hartman (not yet implemented). The focus of the guiding camera can be changed using the text box in the last row or by moving the slider.

The star catalog un use by Skymap is indicated in the top left box; wich can be clicked to see the available options and eventually switch catalogs.

skymap_guider.png
Figure 6. Skymap and Guider GUIs

 

Once the probe is at the desired position it should be possible the see the guiding star to appear on one of the guider displays (see fig. 4).

The guider focus can be adjusted by clicking and moving the slide bar button on the guider GUI or just writing the desired focus value next to it. Each time the telescope focus is modified (e.g. to apply focus offsets between filters) the guider foucs has to be modified by the same amount.

To interact with the guiding software the corresponding screen has to be selected on the Belkin KVM which is mounted on the rack next to the observer workstation

TCS_GUIDER_Computer.jpg
Figure 7. TCS and Guiders Monitor
 
 
kvm_switch.jpg
Figure 8. KVM switch
 
 

At the beginning of the night a software reset of the camera is recommended by typing DSPI. It also recommended to check that the PA and PX parameters are set according the values in Table 4. The cooling system is initiated by entering TEC 1.5. To adjust the range of intensities between black and white displayed the command SPAN is used (e.g. SPAN 1000). In order to guide, the guiding box has to be moved on the star image using the cursors. To change cursor steps use the keys INSERT and DELETE.

Guiding is started with <F3> and it is stopped with <F1>.

A full detailed description of the guider software (GCAM) can be found at this address: http://www.lco.cl/telescopes-information/magellan/operations-homepage/magellan-control-system/magellan-manuals/gcam/gcam-usermanual.pdf

 

ScreenShot_Guiderpa210.png
 
Figure 9. Guider Display Screenshot


End of night:


  • Push ASCENCION RECTA to stop tracking.

  • On TCS type DOME IDLE and DOME PARK, to park the dome to the South.

  • Type COVER on TCS

  • From the LPLC panel close the dome, turn the lights on and raise the wind screen.

  • Go upstaris, raise the platform and replace the telescope cover. Lower the platform all the way again.

  • Turn off the dome lights.
  • Turn the fans off in adjacent room.

  • On TCS type ZENITH to park the telescope.

  • Set the guider at the park position.

  • On guider console type SPAN 99999 (or another big number) and TEC 0.0 to stop cooling.

  • Turn off instrument power and console (rotate key).

  • Fill out the C40 daily report at http://alyth.lco.cl/obsreports/

Appendix

Macros

Macros can be used by placing a text file in the DATA directory of the observer’s account on puma.

The file could be something like this:

filter g

exptime 12

start

filter B

exptime 30

start

filter u

exptime 100

start

To run the macro, the file name has to be specified on the window (usually empty) next to Execute on the CCD GUI, for example: /Users/obs1/DATA/macro_test Then the macro is started by clicking on the Execute button.

Tables

Table 1. Quantum efficiency
Quantum Efficiency

350 nm

42.1 %

400 nm

79.7 %

500 nm

85.8 %

650 nm

92.0 %

900 nm

62.5 %


Table 2. Gain and RON
Quadrant Gain (sigma) Readout Noise (sigma)

CCD1

1.045 (0.029)

3.026 (0.093)

CCD2

1.018 (0.028)

3.206 (0.102)

CCD3

1.003 (0.027)

3.414 (0.103)

CCD4

1.029 (0.029)

3.154 (0.099)


Table 3. CCD characteristics
Detector E2V CCD231-84

Pixel scale

0.435 arcsec/pixel

Readout time

37 s

Field of view

29.7 X 29.8 arcminutes


Table 4. Guider parameters
Guider # PA PX FOV

1

-210

0.163

2.78 arcmin

2

-30

0.163

2.78 arcmin

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