This manual gives general instructions for operating the Fan Mountain 40-inch telescope, the filter control system, and the autoguider.
Fan Mountain Observatory is a research facility of the University of Virginia Department of Astronomy. The instruments are being used for graduate student teaching and the research programs of faculty and their students. You should conduct your work with the utmost care, patience, and forethought, keeping in mind that the equipment is delicate, complex, and expensive to maintain.
To minimize the potential for accidents, you should have a clear idea of your observing plan for the night, including the optimal observing times of your target and calibration objects, lists of coordinates and finder charts, and an efficient plan for minimal changing of filters. Do not neglect to obtain the necessary set of bias frames and flat fields for calibration, or the rest of your data will be worthless.
If anything in this manual is unclear, consult the TA or appropriate faculty member for clarification. As with all delicate equipment, NEVER force any moving part beyond reasonable and expected resistance. Always keep track of the telescope position in relation to the sky, dome, and objects within the dome. NEVER touch any optical element. Oils from your skin will permanently embed into glass surfaces and optical coatings. It is better to leave small amounts of dust on optical surfaces than to risk scratching or marring them with attempts at cleaning. If dust is a serious problem, ask the TA, Jim Barr, Charles Lam, or a faculty member to remove it with dry nitrogen. If, while in the control room, you hear any peculiar noises or have any uncertainty about the location of the telescope or dome, you should make the trek up one flight of stairs to check the dome in person. If you are uncertain about any aspect of operating the telescope, or any other piece of instrumentation, STOP and ask someone. THINK BEFORE DOING.
Home phone numbers: Fan Mountain caretaker Nick Nichols (979-0684), David McDavid (434-985-4378), Jim Barr (540-832-5304), Steve Majewski (434-975-6435). In case of emergency don't hesitate to call, but please try not to call unless it is absolutely necessary.
The Fan Mountain 40-inch telescope has an f/13.5 Schmidt-Cassegrain optical system with a 40-in (1-m) aperture, a focal plane image scale of 15.3 mm, and a corrected photographic field of 50. It has a computerized telescope control system (TCS) developed by DFM Engineering, Inc. and described in detail in the TCS486 Operations Manual on the bookshelf in the control room.
A pair of fans inside the telescope tube near the corrector plate can be turned on with the toggle switch on the west side of the telescope tailpiece. Power to the toggle switch is on only when the CCD switch on the bottom rack panel (Fig. 2) in the control room is on. Running these fans helps to improve tube seeing under some conditions.
The filter wheels inside the telescope tailpiece above the CCD camera shutter can be operated from the filter control panel on the south face of the tailpiece when the switches are set to LOCAL or from a computer in the control room when the switches are set to REMOTE. When used with the GenI CCD camera the filter wheels can also be operated from the camera control program through a popup window, and filter information is recorded automatically in the image FITS headers (see documentation for the GenI camera).
Filter wheel A (the lower one, also known as filter wheel 1) has 4 openings spaced at 90 intervals and holds 6-in square filters. Filter wheel B (the upper one, also known as filter wheel 2) has 6 openings spaced at 60 intervals and holds 4-in square filters.
To load a filter into a filter wheel, first open the filter wheel access door (the rectangular panel above the filter control panel held shut by clamps) so you can see the filter wheels inside the tailpiece. Switch the filter wheel to LOCAL and use the SLEW button on the filter control panel to rotate it. Open the lock at the edge of the filter opening you select, slide the filter into the slot, then close and gently screw down the lock with your fingers. The filter opening in the telescope light path is the one diametrically opposite the one at the access door.
Available filters include standard 4-in square UBVRI and 6-in square Washington filter sets, a 4-in square H-alpha/red continuum interference filter pair, 4-in square H-beta, OIII, NII, and SII interference filters, and a small collection of other assorted interference filters, including a DDO51 filter. The filters are stored away from moisture, dust, and extremes of temperature in wooden boxes on the table below the bookshelf in the control room and should be kept there except for periods of active use when conditions are not potentially harmful.
Filter observations can be calibrated with observations of Landolt standard stars listed in the catalog on the bookshelf in the control room. See other references on the bookshelf for details of the filter characteristics, instructions on using IRAF to reduce CCD photometry data, and methods for the transformation of CCD photometry data to standard systems. Some useful references are:
Almost all research facility telescopes are equipped with an auxiliary autoguider, a device that assists the main telescope in tracking a target for a longer time than the telescope alone is capable of. The 40-inch Fan Mountain telescope can track a star unaided for approximately 3 minutes (when pointed within of the zenith). With the autoguider, exposures of up to 30 min have been tested, and longer ones are possible. The autoguider was built during the summer of 2001 by Jim Barr, Jeff Crane, Charles Lam, Eugene Lauria, and Kiriaki Xilouris.
The autoguider consists of a CCD video camera (SBIG STV) connected to an 8-inch Meade LX Schmidt-Cassegrain telescope that is mounted on the main telescope tube, supported by a pivot stage. This structure enables limited but independent motion of the Meade with respect to the main telescope tube, increasing the possibility of finding a guide star close to the target area. Between the Meade and the STV there is a focal reducer to optimize the image scale for autoguiding and a JMI motorized focusing stage to enable remote focusing of the guider from the control room. The manual focus knob on the Meade telescope has been disabled and should not be used. Characteristics of the autoguider system are given in Table 1.
The autoguider can be controlled from its controller box, which is mounted on the west side of the telescope tailpiece, or remotely from the control room using the autoguider PC and the SBIG STVRemote application software. The pivot and the focusing stages are normally operated from the control room. A special cable is available to operate them from the dome room.
To operate the Autoguider make sure that:
On the autoguider PC click on the STVRemote icon to start the remote control software (See Fig. 6.) You will normally see ``Link Established'' in the PC Message window as the serial link to the controller box is automatically established. If you do not, you may need to select either COM1 or COM2 (whichever works) from the Link pulldown menu to establish the link.
Click Setup, then click Parameter to cycle through the Setup menu. Click Value to adjust a parameter. Most of the Setup parameters should be correct by default, but you can easily cycle through the choices and select any options you want. You can dismiss the Setup menu by clicking Setup again. All the buttons on the STV Remote virtual control panel work according to this model.
A filter wheel inside the STV camera head allows selection of an R, G, B, or Clear filter to approximate the passband being used by the imager on the main telescope in order to reduce autoguiding error due to differential atmospheric refraction. The filter position is changed from the Setup procedure described above, where it appears as one of the adjustable parameters.
Sometimes a commanded change of filter or the function of ``Covering the CCD'' in Tracking or Calibration mode will stall, but this is easily remedied. Click Setup and advance to ``Adj Filter'' in the Setup menu sequence by clicking Parameter a few times. If the display reads ``Fail'', click Value repeatedly to adjust the displayed voltage until the ``Shtr'' position is as close as possible to the optimum value of 7.5%. The display will then begin to read ``Pass'' and the malfunction will be corrected.
To begin taking images click Image, then click Parameter repeatedly to see the adjustable parameters, then set each one by clicking Value. Choose a likely exposure time (say 5-10 s), set Continuous, then click Image again to start a continuous video stream on the monitor cube.
Focus the 8-inch Meade by pushing the buttons on the focus hand paddle on the control room table while watching the video monitor. You can adjust the focusing speed with the rotary button between the IN and OUT focus buttons. Move the Meade about its zero point position with the small hand paddle on the table to find a star if none appears on the monitor.
When you have the 40-inch pointed at an object and are ready to set up for autoguiding, use the same procedures to find a bright guide star and an appropriate exposure time and to adjust the focus for the filter you have selected.
Click Calibrate and set AUTO Mode. Click Calibrate again to start the STV automatically learning how far and in what directions its four relays move the telescope for guiding, by exercising the relays and measuring the resulting displacements of the selected guide star. If the calibration sequence is successful, the Message window will show ``Passed'' and the monitor cube will display four arrows showing the motions produced by the relays.
To start tracking click Track, set AUTO Mode, and click Track again. The tracking status will be displayed on the monitor cube and in the Message window.
The Monitor functions include monitoring the seeing, checking the optical quality of the Meade, and measuring the periodic errors in the drives.
If the STV doesn't behave the way you expect it to, consult the Operating Manual STV for much more detailed information on its operation. You will also find many more functions which are not mentioned here, as well as complete instructions for running the AUTO Mode procedures manually with a great variety of interactive options.
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