To Table Of Contents
icon, you can click on it to return to this point.
There are two secondary mirrors, each giving the same Cassegrain focal ratio, but one being undersized for IR observations (in recent years, we have not used the IR secondary). The secondaries are centrally supported and defined. The new secondary mechanism (HEXAPOD) allows full remote control of the position of the mirror for collimation; however, the observer normally can only use the focus movement.
The fork mount uses direct-friction drives, allowing very fast slewing but having the potentially dangerous feature that the telescope can be moved by hand when the motors are not engaged. The drive motors are controlled via a PC (the "mount PC") running software supplied by Comsoft. The dome position is encoded, and when properly set will follow the motion of the telescope accurately.
An autoguider program running on a PC (the "guide PC") allows movement of the TV pickoff mirror, in the "topbox", focus of the TV, as well as autoguiding. The TV field is presently about 2x1.5 arcmin. Turn on the power for the guide camera. You will find the electronics box and its switch mounted on the mirror cell. Make sure the guide PC is booted first. If you need to reboot the guide PC, type "Ctrl-Alt-Del" simultaneously on its keyboard. The message "You can start Realtime system on the Sparc" will appear on the guide PC monitor after a few minutes. Instructions to operate the guider are available here.
The topbox also has an 8-position filter wheel, controlled by a Sun computer ("flwo48"). The maximum filter size is 4"; inserts also allow 2" square and round filters to be used (vignetting may compromise your observations with 2" filters). Observers are not allowed to change filters; please ask the staff during daytime if you need to change filters.
To Table Of ContentsFor Minicam or 4shooter observers who want the telescope coordinates centered on one of the CCDs, rather than on the center of the array, you must take the following extra steps (see each camera link for more details). After zeroing a bright star on axis, enter the appropriate offsets in the offset menu (e.g., +170 -40 for chip 2, amp 3 on Minicam, or -350 -350 for chip 3 on 4shooter), click on "Move to Manual Off" and thus move the telescope so that the setup star is at the center of your favorite chip/amp. Cancel out of that window. Now use the "Set TelePos" from the TCS window. Make sure the coordinates shown are those of your star.
If you don't see the star, with the TV on-axis, first consider the possibility that the previous observer zeroed the telescope away from the center of the array. Try reversing the above offsets (depending on whether you are using Minicam or 4shooter) and see if the star appears in the TV.
If the coordinates are way off and you can't find any stars in the guide TV even after entering the offsets above, you should start by going to zenith. Stow the telescope from the Tele Tasks menu and type "exit" in the command window to exit the system. Then, go into the chamber, verify you are near zenith by eye, and use the bubble levels on the North (start with this one to set RA first) and East sides of the topbox. Move the telescope with the hand paddle if the drives are enabled, or if the drives are disabled, by pushing and pulling manually until each bubble is centered in its level.
Once you have achieved level Nirvana, go back to the control room and if enabled, disable the telescope drives on the rack. Next, exit TCS on the mount PC using the menu bar at the bottom of the screen. Select and click on the manual exit option (or hit the appropriate key) at the extreme right-hand side of the menu bar. You will be offered a window with options; hit ESC 3 times and then RETURN, which will finally shut down TCS. Restart TCS on the mount PC by double-clicking on its icon (in the middle of the monitor), then click once on the TCS menu that appears at the bottom of the screen, then hit RETURN once you get a blue window. At that point, you can enable the drives again, restart the system with go4 or gomin on flwo48, enable tele and dome tracking, and proceed with your observations. Make sure to re-check the pointing by going to a bright star as indicated above.
If you have gone through all the steps above, you are ready to focus the telescope (see the Minicam or 4shooter primer, Telescope Focusing).
You should be set to observe.
To Table Of ContentsThere is a large two-speed fan that can be turned on after the dome is opened at night (to the South of the telescope). The low speed is preferred by some, but there is no established dogma.
To Table Of ContentsThere are several macros in the Realtime system that allow you to take flats in all of your filters with a single command, say while you are enjoying dinner. Be sure to turn off the lamps when you are done. Close the mirror covers ONLY at zenith!
To Table Of Contents
cd /data/flwo48 xv -poll -geometry -0-0 -drift -3 -23 -gamma 2.6 -hist outfile.fits.gz&
If you use ssh to login, you should not setenv DISPLAY, as it will be automatically defined for tunneling by ssh. That should pop up an xv window on your screen that will automatically update (every 10 sec) with an image from your guide camera only when guiding is OFF. You may not need this feature if you are not interested in the guide camera view while not guiding. Given good pointing and good sky conditions, the automatic guide star acquisition GstarAq should work without the xv feature. If you are searching for a bright star to adjust the pointing, it may be best to take a quick binned exposure and use it to measure your offsets.
To Table Of ContentsThe software has a protection against slewing too far over. The telescope will not move if you have requested an illegal move. On the mount PC monitor, the word Next will be highlighted in red. It is possible however, to go to the limit by slewing with the hand paddle.
Currently, the limits are: |HA| <= 6 hours, DEC >= -30 degrees and sec(Z) <= 5.0. If you have reached any of these limits, perhaps by moving there with the hand paddle, or perhaps the telescope simply tracked into the western limit, the motors will shut off automatically. The dome may also rotate incessantly. To get restarted, first and most important, find out what you did wrong and correct that. It could be that you have reset the coordinates completely wrong, and then tried to slew to what would have been a reasonable place, but which was rendered impossible to achieve by the zero-point mistake.
In the control room, disable the telescope drives. Once you know what you did wrong, go out to the telescope and determine whether a move in RA or in Dec is needed. If an RA move is needed, push on the fork (rather difficult) for a few inches of motion. If a Dec move is needed, gently push on the top ring in an upwards direction for about a foot of motion. Now clear the "Panic" mode on the mount PC screen by typing "F9 F10 F9" (perhaps several times) on its keyboard. The dome should stop moving at this point after it has homed itself. Once both the "Panic" message and the "Disabled" messages are gone, you may turn on the drive enable switch.
The telescope may now be moved with the hand paddle or under computer control (please don't repeat the previous move). You should check the dome to make sure it is homed; if not, use the home dome button in the TCS window (on flwo48), under "Tele Tasks."
If the filter wheel and/or the pickoff mirror stop responding, or on startup the sytem hangs and fails to produce the TCS window, you should cycle the power to the topbox. First exit TCS (type "bye" in the command window). Second, go into the chamber and turn off the power switch, on the South side of the mirror cell. Note: the switch may not be exactly as shown in this image, but it should be nearby on the South side of the cell. It is marked "MOTOR CONTROL RESET SWITCH." Turn it back on after a few seconds. Third, reboot the guide PC, type "Ctrl-Alt-Del" simultaneously on its keyboard. The message "You can start Realtime system on the Sparc" will appear on the guide PC monitor after a few minutes (you should hear homing motors inside the topbox). Finally, restart TCS, by typing "gomin" for Minicam ("go4" for 4shooter) , and after a few more minutes, you will be back in action. If you are unsure about any of these steps, please call a staff member.
If the mirror covers fail to open or close completely (e.g. 1 petal sticks), please call a staff member for guidance.
If your command window is still responsive, type "exit" there. When all the tcs-related windows are gone, type "gomin" (Minicam) or "go4" (4shooter).
If that doesn't work, it is probably necessary to kill off tcs manually and start over. In any xterm other than the command window, type killcom. You should see the command window and all tcs-related windows disappear within a few seconds. You are then ready to restart by typing either gomin (Minicam) or go4 (4shooter).
If none of the above works, it's probably necessary to reboot flwo48 and start over. If you do that, you might as well go through the whole telescope startup routine again.
To Table of Contents
