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The Fan Mountain Observatory 31-inch Tinsley Reflector


31-INCH TINSLEY REFLECTOR

(Rev. August 06, 2007)

General Information

The 31-inch (79 cm.) Tinsley reflector is located on Fan Mountain. The telescope is a general use reflector originally used with photomultipliers and a photographic plate specrograph. Currenty extensive hardware upgrades and instrumentation efforts are underway to transform the observatory into a more modern research facility capable of IR imaging and grism spectroscopy. This upgrade and instrument project is funded through an NSF grant. Projects in the upgrade include: a drive system upgrade, a new IR Carmera, and an autoguider.

Due to the status of this upgrade project the 31-inch will only be avaialable for public nights, twice a year. For more information about the project or use of the telescope please contact Michael Skrutskie (mfs4n@virginia.edu)

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The 31-inch (79 cm.) Tinsley reflector is located on Fan Mountain. Here is some information about the telescope.

Comments
Primary 31 inches in diameter, 120-inch focal length, 6.25 inches thick,
wt. = 368.8 lbs., the hole is 8.75 inches in diameter. All
mirrors are Pyrex.
4X Secondary 8.48 inches in diameter, 1.75 inches thick. System focal length
480 inches. f/16
8X Secondary 5.474 inches in diameter, 0.875 inches thick. System focal
length 960 inches. f/32
Plate scale 16.9 arcsec/mm (calculated). Measured value = 16.2 (Zissel)
to 17.5 (Rosenberg) arcsec/mm.
Limiting visual magnitude Estimated at approximately 16 mag. on the best nights.
Dome 24 ft. Observa-dome.

Field Power
Finderscope 5" Maksutov 30' 75X
3" finder 2-3 15X
Eyepiece Black 15'
25 mm. + Xfer system 2.75' 960X
25 mm. 6' 480X
12.7 mm. 2' 950X

Care of the Telescope

The telescope should always be stored in a horizontal position in order to prevent the accumulation of moisture on the main mirror. The telescope should not be left unattended for more than a few minutes unless you turn off the drive and either move the slit away from the telescope or close the dome shutters.

Opening Up

  1. Locate light switches. The red and white lights in the dome room are controlled by rotary dimmer switches to the right of the door as you walk in.

  2. Open dome shutter.

    The dome shutter is opened and closed by plugging in the plug hanging from the right side of the shutter. Plug into the wall outlet and hold switch in direction wanted (open to right, close to left). Letting go of switch will stop the dome shutters. Be careful not to break chain when dome is fully open or closed. The limit switches do not always work.

    Unplug and hang the cord over the extension arm after the slit is open to prevent the cord from catching on projections as the dome is rotated.

  3. Turn on telescope main power switch on the west side of the pier.

  4. Open primary mirror covers, remove covers for secondary mirror and finder scopes.

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    The main mirror cover can be removed by simply pulling on the handles on the swing open doors. The doors are held closed by two latches (one at the top and the other at the bottom of the doors when the telescope is horizontal) which will give under pressure. Rotate the small catches into the handles to ensure the doors stay open. The doors must be pushed closed individually, closing the one closest to pier first.

    The secondary cover is removed by grabbing the handle and rotating the cover until the slots line up with the catches; the cover can then be pulled off. Be careful when removing and replacing the cover and make sure that the slots and the catches are aligned.

  5. Push set button on control console next to drive rate switches.

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  6. The RA and DEC. clamps, dome rotation, focus, slow motions, and offset trigger are located on the control box hanging from the telescope. Auxiliary dome rotation controls are located on the panel above the console.

  7. The drive is turned on by the switch on the upper left corner of the console.

  8. Go to the Control Room

The Control Room

The telescope is controlled electronically by a computer system which is composed of entirely commercial hardware and software. The hardware and software manuals can be found in the Control Room.

Initializing the coordinate readout software:

  1. Starting the alignment procedure.

    1. Move the cursor to the Telescope option in the menu bar at the top of the screen using the mouse.

    2. Press and release the left mouse button. The Telescope menu will appear.

    3. Move the cursor to the Link option in the menu.

    4. Press and release the left mouse button. The Link menu will appear.

    5. Move the cursor to the Establish... option in the menu.

    6. Press and release the left mouse button. The `Alignment Procedure window will appear on the screen directing you to start step 2.

  2. North Celestial Pole alignment.

    1. Point the telescope at 90 degrees declination (the north celestial pole).

    2. Move the cursor to the OK button in the Alignment Procedure window using the mouse.

    3. Press and release the left mouse button. The Alignment Procedure window will change directing you to start step 3.

  3. First alignment star.

    1. Changing the alignment star (optional)

      Use the menu bar and icons below it to display the desired star on the screen.

      Use the mouse to place the cursor on the desired star.

      Press and release the left mouse button. The Object Identification window will appear displaying information about the star and buttons.

      Move the cursor to the Alignment Star button in the window using the mouse.

      Press and release the left mouse button. The display will now show the desired star as the alignment star.

    2. b) Point the telescope at the alignment star.

    3. c) Move the cursor to the OK button in the Alignment Procedure window using the mouse.

    4. d) Press and release the left mouse button. The Alignment Procedure window will change, directing you to start step 4.

  4. Second alignment star.

    1. Changing the alignment star (optional) - See section 3a.

    2. Point the telescope at the alignment star.

    3. Move the cursor to the OK button in the Alignment Procedure window using the mouse.

    4. Press and release the left mouse button. The angular separation that the encoders swept out, the calculated angular separation between the two alignment stars and their difference will be displayed in the Alignment Procedure window. The difference is zero if the alignment is perfect.

    5. If the alignment difference is less than five degrees move the cursor to the Accept button in the Alignment Procedure window using the mouse.

    6. If the alignment difference is greater than five degrees move the cursor to the Reject button in the Alignment Procedure window using the mouse. Restart the alignment proceedure at step 1. If the difference persists, a hardware problem is the most likely cause.

    7. Press and release the left mouse button. The display will use the Night Vision colors and display a bulls-eye indicating where the telescope points on the sky. As you move the telescope the bulls-eye will move accordingly. The telescope now has control over the screen so that the bulls-eye never leaves the screen.

  5. Changing the position display.

    1. To select a numerical display of the telescope position instead of the default graphical display:

      Move the cursor to the Telescope option at the top of the screen using the mouse.

      Press and release the left mouse button. The Telescope menu will appear.

      Move the cursor to the Digital Setting Circles... option at the bottom of the menu.

      Press and release the left mouse button.

    2. To change back to the graphical display, press and release the left mouse button or space bar on the keyboard.

  6. Temporarily regaining manual control of the display.

    1. Move the cursor to the telescope icon at the top of the screen and under the menu bar.

    2. Press and release the left mouse button. The icon will change, indicating that telescope control of the display has been disabled.

    3. To re-enable telescope control, repeat steps A and B.

Closing Down

  1. Turn off drive.

  2. Place the telescope in a horizontal position and cover both primary and secondary mirrors. Make sure both top and bottom catches on the primary doors are fastened and that the secondary cover is completely on. Replace covers on finders.

  3. Close dome by rotating the dome until the cord is near a socket. Unhook the cord and plug it in. Make sure slit is completely closed.

  4. Fill out log with closing information.

  5. Turn off all lights and check that nothing has been left on.

  6. Close and lock the door behind you.

The Control Paddle

RA and DEC clamps: These switches unlock the RA and DEC axes. When the lights above the switches are on the axis is unlocked. These switches control locking motors so the lock takes a few moments to act. If the switch is thrown or reversed rapidly, the state of the lock might not change. (Sometimes throwing the switch fails to do anything.) If the axis fails to respond as expected, recycle the switches. When the declination axis is unclamped, the declination slow motion centers (the slow motion is a motor driven offset arm and it can run out of travel). Sometimes, this motor ``runs away'' and runs the arm to the limit. Such action causes an abnormal noise and should be countered by pressing the reset button. (This can happen spontaneously as well as when the axis is unclamped, and it always happens when the power is turned on.)

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Focus: This switch racks the secondary in and out in order to focus the telescope. This is connected with the focus readout on the desk.

Dome rotation: Rotates the dome. Up is clockwise, down is counter-clockwise.

Fast-Slow switch: Sets the slow motion rate to fast or slow at the operators discretion. Up is fast, down is slow.

Slow motions: The four buttons actuate the slow motions. The center switch changes the directions of the buttons (the northward dec changes to southward, the westward RA button is now eastward, etc.). If the slow motions balk or act with abnormal noise, 1) check rate and make sure right speed is selected; 2) recycle locks; 3) hit reset; 4) hold button and the motion might straighten out on its own. (This is the last resort.)

Spare: Not connected to anything.

The Guide Box

The guide box was designed to provide finding and guiding optics so they would not have to be duplicated on each piece of equipment. To this end the box contains an angled mirror to intercept the light beam. The mirror is controlled by a knob on the left side of the guide box. This knob has three positions: full clockwise, which moves a small hole into position in the middle of the light path; a center position, which completely intercepts the beam with the mirror; and a full counter-clockwise position which intercepts virtually none of the light beam as it moves a large hole into position.

The guide box also contains two power panels for powering equipment on the tailpiece. These panels are normally ``cold'' and have to be plugged in to power to operate. The best place to plug in the panels is the 110V and 6.3V socket on the telescope close to the declination axis. The back left power panel can be plugged in there and the front right panel can be plugged into the back panel.

The whole guide box can be rotated into a comfortable position by loosening the single set screw in the base of the telescope. Be careful not to break power cords running from the guide box to sockets elsewhere when rotating the guide box.

Alcove and Circuit Breakers

The alcove of the dome contains the circuit breakers and power supply for telescope, with the exception of the main circuit breaker which is located in the ``garage'' of the station house. (It is marked ``small bldg.'' and is #16.)

The alcove switch controls the overhead light in the alcove; the outside switch controls the white light just outside the door. The switch marked ``station house'' controls the bright outside light on the bridge from the station house to the 1 meter dome.

Figure 2 gives the layout of the outside wall. The main fuse is on the 220V. line coming into the dome. If any unusual electrical connections seem to be occurring, particularly if the dome will not rotate, it could be due to one side of the 220V line being bad. The power rack in the dome is the power supply for the telescope. Usually any electronics necessary for the instrumentation on the telescope, such as photometers etc., is located in a separate rack. Underneath the desk on the rack is the power supply proper. This contains the on-off switch for the telescope and, on the right side, the rest button for the setting circles. It also contains a switch to reverse the sense of the slow motions depending on which side of the pier the telescope is. Under the power supply is a panel of fuses marked according to function; under this is a panel of indicator lights to indicate the status of the various relays that control motor direction, etc., for the telescope.

The heaters and air conditioner in the dome were originally intended to provide a dual service of temperature control and dehumidification. The intent was that the air conditioner would keep the dome cool during the day while the heater would prevent dew from forming. The humidistat should be off while observing.

Equipment used with 31-inch telescope

  1. Single-channel pulse counting photometer
  2. Dual-channel photometer
  3. The Ridell-Spotz Spectrograph
  4. An Eyepiece

EQUIPMENT LOCATION
Offset guide plate Fan
Black eyepiece plate Fan
1 1/4 inch eyepiece focusing mount Fan
Black eyepiece Fan
25 mm eyepiece Fan
12.7 mm eyepiece Fan
transfer system Fan
8X secondary Shop
4X secondary on telescope

FILTERS SET CONDITION
Stromgren Set 1 poor
Set 2 poor
Set 3 poor u labeled non-standard
Johnson Set 1 o.k.
Set 2 o.k.
DDO $\lambda$4166 very good
$\lambda$4516 very good
$\lambda$4256 very good
H$\beta$ w&n Set 1 very bad
Set 2 very bad
H$\alpha$ w&n terrible

Log Procedure

All observers are requested to enter the following information in the logbook. Entries are to be made at both opening and closing times. If weather doesn't allow observing enter as many items as possible.

Explanation: On the first line for the night the observers name and equipment are to be entered. The following conventions can be used: photometer 1 = single channel; photometer 2 = dual channel photometer.

The next two lines are the opening and closing records, respectively. The following explain the entries.

Opening or closing record:

  1. Date - month/day/year

  2. EST - Eastern Standard Time

  3. Temp - Temperature from thermometer

  4. Hum - humidity from dome hygrometer

  5. Wind - estimated wind speed

  6. % clouds - estimate of percent of cloud cover during night

  7. Transp - transparency in clearest regions during observations on scale of 0 mag to 5 mag based on apparent magnitude of faintest star visible to naked eye

  8. Seeing - estimated mean seeing disk in seconds of arc

  9. Hrs. worked - number of hour during which observations were made or attempted

  10. Comments - list observing program, problems, or other general remarks you feel appropriate. Problems should also be reported to the proper individuals the next morning, in a trouble log, and/or to email trouble log trouble@astsun.astro.virginia.edu.

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