x x y
= 45.6 x 50.6 mm, which corresponds to an angular range of motion on
the sky of RA x dec = 1.14
x 1.27 degrees. The centre of the field
is normally aligned with the optical axis of the 30-inch telescope.30-inch Telescope Guiding
Table
of contents
The guider
hardware
Starting
the guider PC computer and SBIG ST-4 camera
Finding a
guide star
Basic
operation of the SBIG ST-4 guide camera
Connecting
up the guider PC computer and SBIG ST-4 camera
The guider
PC computer
Model
ST-4
Star Tracker Imaging Camera: Operating Manual
ST4
Software Addendum: Version 2.06 for the IBM PC
Application
note: More on Tracking with the ST-4
Application
note: Dark Frames and Co-adding Images
Version 4
ROM upgrade to ST-4: User instructions 251191
• The guider telescope is a 6-inch f/15 refractor mounted on the side of the 30-inch telescope. Its optics surpass the Rayleigh criteria and deliver a diffraction limited image in good seeing with an Airy disc diameter of 1.8 arcseconds at 550 nm.
• A flip mirror near the focus of the guide telescope selects between the following two foci:
-- An acquisition focus with a TeleVue 32 mm Plössl eyepiece which yields a magnification of 71x and a field size of 0.7 degrees. There is some vignetting in the outer field.
--A guiding focus with a TeleVue 3x Barlow lens. Two options are available at this focus:
* An SBIG ST-4 CCD camera operated by a PC computer is available for remote guiding. The physical array size is 192x165 pixels, and the physical pixel size is 13.75x16.00 µm. The angular array size on the sky is 79x79 arcseconds, and the angular pixel size is 0.41x0.48 arcseconds.
*A 12.5 mm Plössl eyepiece with a variable illuminated reticle is available for visual guiding at a magnification of 550x.
• At the
focus of the guide telescope is an x-y stage which allows offset
guiding, x is normally aligned with right ascension, and y with
declination. The physical range of motion of the x-y stage is x x y
= 45.6 x 50.6 mm, which corresponds to an angular range of motion on
the sky of RA x dec = 1.14
x 1.27 degrees. The centre of the field
is normally aligned with the optical axis of the 30-inch telescope.
Starting the guider PC computer and SBIG ST-4 camera
• If
necessary, check the cabling of the guider PC computer and the
SBIG ST-4 camera as described in the section Connecting up the
guider PC computer and SBIG ST-4 camera. See photo.
• Power up the SBIG ST-4 or confirm it is on. When on, the LED alphanumeric display on the SBIG ST-4 controller box is illuminated. It takes approximately two minutes for the CCD to cool to its operating temperature after being turned on. See photo.
• Press the interrupt key on the SBIG ST-4 controller box. The alphanumeric display, if uncovered, will then say hello.
• Power
up the guider PC computer and its monitor, or confirm that they are
on.
• Change directory on the guider PC computer to the directory holding the SBIG software with the command: cd \ccd
• Start the CCD software with the command: ccd. Approximately five seconds after this command is issued, the ccd program will report the baud rate established on the communication link between the guider PC computer and the SBIG ST-4- This should be 57,600 baud.
• When the program ccd starts, it reads in the configuration file ccd.cfg to set up the SBIG ST-4. Unless the previous observer has used an unusual setup for some reason, the ST-4 is probably ready to go.
• Loosen
the four clamps on the RA (x or top) stage of the offset guider, and
the three
clamps on the Declination (y or bottom) stage.
• Put the flip mirror in the acquisition position by turning its actuator knob clockwise.
• Make sure the acquisition eyepiece is in the acquisition eyepiece holder (and not the spare eyepiece holder [not yet installed]).
• Find a guide star in the acquisition eyepiece by moving the eyepiece around the field with the RA and dec stages. The stages are moved by turning the silver knobs that drive the stages through rack and pinions. Most stars you see will be bright enough for guiding, but choose the brightest star in the magnitude range 6—9 that can be found in a reasonable amount of time.
• Centre the guide star in the field.
• Swap the guide eyepiece and acquisition eyepiece, make sure the reticle in the guide eyepiece is on (illuminated), and centre the guide star on the reticle.
• Tighten firmly the seven clamps on the RA and dec stages, making sure that the guide star doesn't more too far from the centre of the field.
• Swap back the acquisition eyepiece and the guide eyepiece.
• Put the flip mirror in the guide position by turning its actuator knob counter clockwise.
• Confirm as follows that the x dimension of the CCD is aligned with RA. As judged by eye, the long axis of the label on the back of the ST-4 should be parallel with the RA stage on the guider.
Basic operation of the SBIG ST-4 guide camera
• A detailed description of the ST-4 and its operation is given in the SBIG manual, Model ST-4 Star Tracker Imaging Camera, and the accompanying application notes. In practise, very little of it need be used for remote guiding.
• General operation of the program is as follows:
— Exit any menu or mode of operation by pressing the ESC key.
— Menus are selected from the menu bar that is along the top line of the main screen by either 1) typing the highlighted letter of the required menu name, or 2) using the left arrow or right arrow keys, followed by the Enter key.
— Items in the menus are accessed using the up arrow and down arrow keys followed by the Enter key, or by typing the highlighted character for that menu item.
• Normal setup for remote guiding is as follows:
— Enter the Camera menu and set the gain to 4x (faint stars)
— At night, enter the PC menu and select NiteVision.
— Enter the Focus menu and set the following items. Only press Enter after the last item in entered, otherwise use the arrow keys to move between items. Set the Exposure time to 1 second, set Autocontrast to yes, and set the Frame size to track. Press Enter. A single full frame will be taken and displayed with a 33 x 27-pixel box superimposed.
• After
the full CCD frame has been displayed, use the arrow keys to centre
the 33 x
27-pixel track frame on the guide star. Press
Enter. (equivalent to 10x10 LF1 pixels)
•
The image within the track frame is repeatedly updated on screen with
a cross hair superimposed. With a one second integration time, the
image is updated every 2.6 seconds.
• Use the control room telescope handpaddle to drive the star onto the cross hair. The ST-4 will normally be orientated so that East moves the star right and North moves the star down. In any case, RA should be the horizontal axis on the screen as the CCD pixels are smaller in this dimension, giving better resolution for guiding in RA.
• Focus the guide telescope to minimize the guide star image diameter on the monitor. The black clamp knob on the rack-and-pinion focusser must be released to focus, and done up snuggly once the image is in focus.
• Start the integration through the PEG, and guide with the hand paddle during the integration. Unless you have the risk gene, only guide in RA.
Connecting up the guider PC computer and SBIG ST-4 camera
Warning: Do not connect or disconnect the CCD Head from the SBIG ST-4 controller box while the box is powered up. SBIG advise that this might cause permanent damage to the electronics.
• Plug the computer CPU enclosure into a power outlet with the CPU power cord.
• Plug the computer monitor into a power outlet with the monitor power cord.
• Connect the CPU enclosure to the monitor by plugging an end of the video cable into the back of each.
• Plug the keyboard into the back of the CPU box.
• Plug the 25-pin end of the 50-foot-long RS-232 cable into the back of the CPU enclosure, and the 9-pin end into the SBIG ST-4 controller box.
• With the power to the SBIG ST-4 controller box turned off, connect the CCD camera head cable to the SBIG ST-4 controller box.
• Plug the 12 volt power transformer into a power outlet, and its output cable into the power connector of the SBIG ST-4 controller box. This connection is currently the power on/off switch.
• The CPU is a 33 MHz 386 with 5 Mbytes of RAM.
• The operating system is MS-DOS 6.22
• The three drives are a 92 Mbyte ESDI drive, a 3.5-inch floppy disk drive, and a 5.25-inch floppy disk drive.
• The video board is an Orchid Pro-designer II with 1 Mbyte of RAM.
• The monitor is a 15-inch NEC MultiSync color monitor.
• The TC-200 Hi-Speed Turbo serial board supports baud rates to 460.8 kbs.
