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 secondary mechanism (HEXAPOD) allows full remote control of the position of the mirror for collimation; however, observers can only use the focus movement.
The fork mount uses direct-friction drives, allowing very fast slewing (about 2 deg/sec) but with the potentially dangerous feature that the telescope can be moved manually when the motors are not engaged. The drive motors are controlled with 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.
A guide system running on a Linux PC allows movement of the guide pickoff mirror, in the "topbox", focus of the guide camera, as well as autoguiding. The guide field is about 2x1.5 arcmin. The power for the guide camera should be left on. You will find the electronics box and its switch mounted on the mirror cell. Make sure the guider system is working first. See directions and operating instructions here: guide system . Instructions to operate the guider via the TCS program are available here.
The topbox also has an 8-position filter wheel, controlled by the guide computer, with an interface showing in the TCS program. Moving by 1 filter takes about 5 seconds, by 2 (3), 10 (15) seconds. TCS optimizes the filter wheel rotation, so no filter move takes more than 15 seconds. The maximum filter size is 4" ; inserts 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.
Observers who want the telescope coordinates centered on one of the Keplercam amplifiers, rather than on the center of the chip, must take the following extra steps. After zeroing a bright star on axis near zenith (with the guider or by taking short exposures), use the "Set TelePos" from the TCS window. Make sure the coordinates shown are those of your star. Once you've verified the coordinates, from the TCS Tele Tasks menu, select "Amp Center" and pick an amp; see the TCS offset entry for more details.
If you don't see the star, with the guider on-axis, first consider
the possibility that the previous observer zeroed the telescope away
from the center of the array. Try reversing the popular offsets
to amp 2, i.e., manually offset by +345, +345 and see if the star appears
in the guider.
If the coordinates are way off and you can't find any stars in the guider view 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 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 gokep 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 described above.
If you have gone through all the steps above, you are ready to focus the telescope (see the Keplercam primer, Telescope Focusing).
You should be set to observe.
There is a large two-speed fan that can be turned on after the dome is opened at night (to the South of the telescope).
If the counts are too low, the dome may be misaligned (view the dome webcam after command lightdome, if misaligned home the dome and try again); the flat lamps may not be working (with the chamber dark, turn on the lamps, view with the dome webcam after command lightdome, if not on call for help); or the CCD may have a problem (restart it using these instructions and try again).
The 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 or by tracking if the initial pointing did not violate a limit.
The pointing limits (set in TCS on the mount PC) are:
|HA| <= 5 hours, -30 < DEC <= +89 degrees,
sec(Z) <= 5.0 and elevation >= 29 degrees, as shown
Rob has a somewhat tighter limit, |HA|<= 4:15 hours (as of 12/29/16), for safety. We can relax this limit (and the DEC, EL and sec(Z) limits) somewhat if you need to work slightly beyond these values. Please request that the limits be changed in advance of your observations, describe the circumstances, and the the limits you need.
There are several possible ways to reach a limit. One is by moving there with the hand paddle. Another is by having the telescope track into the western limit. If the telescope goes to a limit, the motors shut off automatically. The dome may also rotate incessantly. To restart, first and most important, find out what caused the problem. One possibility is that Rob observed a long transit and kept tracking to the West, in which case it shoud raise an error flag for the 1.5m observer.
In the control room, disable the telescope drives. Once you know what went 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 telshell window). Second, go into the chamber and turn off the topbox power switch, on the SE side of the mirror cell. Turn it back on after a few seconds. Third, reboot the guide PC, (see guider manual), for restart info. Finally, restart the system and TCS, by typing "gokep" for Keplercam, 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.
Check to see if the "rguide" window is still on the guider screen. If it's gone, you should restart "rguide" as described here. Your next step is to stop and restart tcs as described next.
If your command window is still responsive, type exit there. When all the tcs-related windows are gone, type gokep to restart tcs.
If that doesn't work, you need to stop 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 gokep.
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.
If you are certain that the power failure caused the generator (at the ridge, for the whole mountain) to kick in, please notify our electrician, Tom Welsh, as soon as possible day or night (see the FLWO directory for his phone number). You can easily hear the generator at the ridge when it's running. Check for its sound if the power has gone off; emergency lights should come on. The normal sequence is for the UPS to go on, so power is maintained until the generator starts, in less than one minute. The emergency lights should then go off. If there is a power failure and the generator fails to start after a few minutes, you should shut down as much equipment as possible, as quickly as possible. Communications equipment has additional power backup, but eventually phones and radios may stop operating. Although phones may not ring, you may still be able to call out for some time.