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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 infrared observations. 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 power for the guide camera. You will find the 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.
The topbox also has an 8-position filter wheel, which is controlled by the 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 4shooter observers who want the telescope coordinates centered on one of the 4 CCDs, rather than on the center of the array, you must take the following extra steps. After zeroing a bright star on axis, enter the appropriate offsets in the offset menu (e.g., -350 -350 for chip 3), click on "Move to Manual Off" and thus move the telescope so that the setup star is at the center of your favorite chip. 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 on Chip 3. Try reversing the above offset (350 350) 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 offset above, you should start by going to zenith. If tcs (or irtcs; we'll refer to both as tcs here) is still running and responsive on flwo48, stow the telescope from the Tele Tasks menu and leave tcs running. If tcs is unresponsive, make sure to kill it, and use ALT-S on the mount PC. Then, go into the chamber, verify you are near zenith by eye, and use the levels on the North 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, if necessary restart tcs 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 4shooter primer, Telescope Focusing).
You should be set to observe.
To Table Of ContentsThere is also a fan that can be turned on after the dome is opened at night (to the South of the telescope). A low speed seems to be satisfactory, 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 eating dinner. Be sure to turn off the lamps when you are done. Close the mirror covers ONLY at zenith!
There is also a new script that you might try for U band flats.
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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 rtshell 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. 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 "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 that doesn't work, it is probably necessary to kill off tcs
and start over. Go to the window where you started tcs, type
jobs to find its job number, then type kill -HUP
%1, using the actual job number in place of the "1." Then type
ipcs and make sure there are no message queues or shared
memory segments still in use. When you run ipcs, you get
something like this:
4obs@flwo48: ipcs IPC status fromIf there is anything owned by 4obs as above, try rmseg and then ipcs again. If this doesn't work, 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.as of Mon Jul 5 22:42:58 MST 2004 T ID KEY MODE OWNER GROUP Message Queues: Shared Memory: m 0 0x50000049 --rw-r--r-- root root m 5801 0x35000aee --rw-rw-rw- 4obs observer Semaphores:
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