13. Operation of the Steward Observatory 90" Bok Telescope Autoguiders


  1. Introduction and Acknowledgments.
  2. Basic information about the CCD Guider Systems.
  3. Observer and Instrument safety.
    • Contact List
  4. Guider Startup.
  5. Guider Operations and the Control GUI.
  6. Shutting down the Guiding System.

1. Introduction and Acknowledgments.

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2. Basic Information About The Guiders.

  • Instrument: 90Prime
  • Device Names: 90PrimeGuider SN2944
  • Device Size: 512 x 512 (15 x 15 micron pixels)
  • Image Scale: 0.47 arcsec/pixel
  • Field of View: 4 arcmin x 4 arcmin
  • Gain: 3.4 electrons/ADU
  • Readout Noise: 12.9 electrons
  • Dark Current: 3.1 electrons/pixel/sec
  • Full Well: 139,000 electrons unbinned
  • Operating Temperature: ~ -38 C
  • Filters: Same as science camera

  • Instrument(s): B&C and other compatible Cassegrain instruments
  • Device Names: BokCassGuider SN3010
  • Device Size: 512 x 512 (15 x 15 micron pixels)
  • Image Scale: adjustable
  • Field of View: max: 3 arcmin x 3 arcmin for B&C
  • Gain: 3.1 electrons/ADU
  • Readout Noise: 18 electrons
  • Dark Current: 4.5 electrons/pixel/sec
  • Full Well: 76,000 electrons unbinned
  • Operating Temperature: ~ -37 C
  • Filters: unfiltered for B&C

See also the ITL CCD Systems page.

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3. Observer and Instrument Safety (In case you need assistance...).

In case of problems with the guiding systems:

    Please report any problems encountered with the guiding system in use in that night's Trouble Report. Make sure that the "CCD Group" is checked on the trouble report form. Be as detailed as possible in your description of the problem(s). It may also help in diagnosing problems if relevant guider CCD images are saved and identified so that they can be found and examined by support/technical personnel.

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4. Startup of the Guiding System.

At the telescope:

  • If you are using the Prime Focus guider (90PrimeGuider), the system will be powered up as the 90Prime system is normally brought online.
For the Cassegrain guiding system:
  • Turn on the cooling unit, which is mounted on the IIS Rotator. The toggle switch must be pulled out in order to be toggled. A green light on the cooling unit will show when the red button is pushed if the cooling fluid is being adequately circulated to the guider CCD dewar (see the example picture of the cooling unit at the 61" telescope).
  • Turn on the power to the BokCassGuider CCD controller, which is mounted nearby but separately from the cooler.

In the control room:

  • With the autoguiding PC booted, click on the "TELCOM150 Server" and "BokCassGuider" (or "90PrimeGuider" if using 90Prime) icons (in that order). Make sure that there is only one TELCOM150 server running.
  • Once the camera is automatically initialized and ready for use, one may set parameters, take pictures, guide, etc.
  • The guider can be controlled from either the autoguiding PC or by using the mouse associated with the computer's second monitor located next to the second display of the TCS screen at the instrument workstation.

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5. Guider Operations and the Control GUI.

    The Guiding control GUI is pictured below (the large window taking up most of the example screenshot) and runs on the autoguiding PC.

    • In the lower right corner of the GUI, 4 large buttons allow you to take a single or repeated exposures with the guider CCD, or start a guiding sequence (either full frame or within the smaller guider window denoted by the white square overlaid on the field of view). Important note: "windowed" guiding in not implemented for this system. That is, make sure that you use the "full-frame" guiding mode.

    • The exposure time can be set using the vertical slide bar to the left of "Acquire" and "Guiding" buttons, or by typing the desired exposure time within the box above the slide bar. Exposures can be as short as 0.1s. The exposure time can be adjusted without stopping an exposure or guiding sequence.

    • Clicking on the desired star in the field will center the guiding box on the star. The size of the guiding box can be adjusted using the horizontal slide bar in the lower left corner of the GUI. Make sure to leave some sky around the guide star so that the background can be properly determined within the guiding algorithm.

    • Messages from the guider to the telescope or to you are highlighted in red and displayed below the guider window size slider.

    • The guiding centroid position can be adjusted using the 'L'eft, 'R'ight, 'U'p, and 'D'own buttons. The number displayed in the center of these buttons is the number of pixels that the guiding window will be moved for each click on a button (this number can be changed via the "Edit guiding parameters" option in the "Parameters" menu). This adjustment of positioning can be made while guiding is in progress.

    • Before guiding can commence, the guider needs to know which way is north and east and the pixel scale. This information is supplied to the guider by doing an x-y transformation (found in the "Telescope" menu). The task steps the telescope through a series of moves. The observer is prompted to click on a chosen star after each move. Moves of 30" in both Dec and RA are adequate for the transformation and won't move the star out of the field of view if one is chosen reasonably close to the center of the field. This step is only needed once even if you are using BokCassGuider and rotating the instrument using the IIS rotator. The software is able to read the IIS position and update the position angles of north and east accordingly one an initial transformation has been performed. Once the transformation is complete, the image will display a compass and the centroiding and image information given along the right edge of the GUI will be correct.

    • While guiding, strip charts that track the guiding corrections in RA and Dec, the FWHM of the guide star, and the guide star flux can be displayed. The tracking charts are shown in the example screenshot on the right side of the screen. This feature is very useful if one wants to track guiding performance, seeing/focus, and whether it is truly photometric. The charts are displayed be default, but can also be selected from the "Display" menu.

    • Cross hairs can manually be placed or erased on the image display. See the "Display" menu to create or destroy markers.

    • The guider can be used to offset the telescope if desired and if an x-y transformation has been performed. Enter the "Telescope" menu (this menu can be reached from going to the top edge of the GUI, or by using the right mouse button while within the image frame) and selecting "Telescope Offset", click on a position within the image frame and then click on a position within the frame that you would like the telescope to offset to. Alternatively, offsets in RA and/or Dec can be entered in the appropriate boxes within the "Offset Telescope" pop up window to move the telescope the desired amount and direction.

    • Many other options are available within the GUI. Explore the menus to see if any will be useful for your observing program.

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6. Shutting down Guiding System.

It is IMPORTANT to shut down the guiding system in the case of threatening weather. If there is no threat of lightning, the guiding system can be left running of the end of the night.

In the control room:

  • Shut down the auto-guider GUI from the "File" menu or from the pop up menu displayed when clicking the right mouse button.
  • Close out any associated guider windows that the GUI shut down misses.

At the telescope:

  • If you are using the 90PrimeGuider, the system will be shut down during the procedure that shuts down 90Prime.
  • Turn off the power to the BokCassGuider CCD controller.
  • Turn off the cooling unit. The toggle switch must be pulled out in order to be toggled.

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Back to the Bok Telescope Manual.

Back to the 90" Home Page.

The 90" cognizant observer is Paul Smith --psmith@as.arizona.edu