Safely closing the APF - For MH Staff

The APF is intended to work in a mode where a remote observer sets up a night’s worth of observations, monitors the beginning of the night, and ensures the facility is safely stowed at the end of the night. Should that not occur, these procedures describe how to safely stow the telescope and dome. The primary objective is to mitigate risk to the facility; restoring the facility to a ready-to-observe status can occur when daytime resources are available.

The procedures outlined here cover different failure modes, and should be attempted sequentially until one of the procedures succeeds.

Shutting down remotely

The telescope should be unreleased to prevent further remote operation, and should immediately be forced to close. This is accomplished via checkapf_tt, which can typically be found here:


In the section labelled “Telescope Tech Controls,” you will need to authenticate with the standard checkRemote TT password, forbid remote/robotic operations, and add a “Change forced close” tag to ensure that checkapf will immediately enforce closure of the dome and mirror cover.

Shutting down locally

If the APF cannot be shut down remotely, but the computers in the dome are still working, it may be possible to access the tools described above from within the APF dome itself, even from a laptop computer. The key capability is being able to ssh into one of the APF Linux hosts (mainz, hamburg, dresden, warsaw) and invoke the above commands.

If access to one the APF Linux hosts is not possible, the telescope and dome can be safely stowed by using the Windows XP telescope control computer.

  1. Locate the monitor and keyboard for the telescope control computer. The telescope control cabinet directly faces the stairwell door to the second level; the monitor and keyboard are in a self-contained rack-mount enclosure that slides out from the middle of the rack.

  2. _images/TelescopeSlew.png

    Telescope slew controls.

    Locate the desktop icon for the telescope control interface. Bring up this interface. If the telescope is not pointed near the zenith (>88 degrees), perform an Az/El slew by entering the current azimuth position, and El=89 in the “Telescope Slew Controls” box along the bottom of the interface, and hit the “Slew” button.


    The dome will track the telescope as it slews in azimuth. Make sure that you are standing clear of the gap between the co-rotating and stationary sections of the floor on the first level.

  3. _images/MirrorCovers.png

    Mirror cover controls.

    Once the telescope is pointing near the zenith, the mirror cover can be safely closed. In the lower-right corner of the telescope control interface, in the “Mirror covers” section, hit the “Close” button. This should immediately begin closing the mirror covers. When complete, the “closed” indicator light in this section of the interface will turn yellow.

  4. Close the telescope control interface, and locate the desktop icon for the dome control interface. Bring up this interface.

  5. The dome control interface shows icons for each different aspect of the dome. Select the dome shutter icon. In this section, hit the ‘acquire resources’ checkbox near the bottom of the interface, and then hit the “Home” button for both shutters. De-select the ‘acquire resources’ checkbox once you have initiated the homing operation.

  6. Close all open interfaces, and restore the computer monitor and keyboard to their original location.

Shutting down manually

If the computer control system(s) fail, but there is still power, it is possible to close the dome shutter via push-buttons inside the dome.

  1. Upon entering the dome, engage the physical e-stop immediately to the left of the exterior door. This will drop power to the telescope, but the telescope will not stop moving before dropping power; allow the dome to coast to a stop before proceeding.

  2. Turn on the dome interior lights using any one of the manual light switches.

  3. Reset the physical e-stop. The dome shutters and mirror cover cannot be moved while an e-stop is engaged.

  4. Locate the stairwell up to level 2; note the presence of the door-warning buttons to the right of the door handle. Proceed to level 2, and then on to level 3.

  5. On level 3, there are four buttons to manually control the dome shutters. These shutter controls are directly behind the stairwell entrance to the third floor, such that you must walk past the Levy spectrometer to gain access.

  6. Once you are standing between the telescope and the shutter, if the mirror cover is open, manually pull the telescope down to the horizon, and “pin” the telescope at the horizon. The pin is located on the interior of the telescope yoke nearest the stairwell. Stowing the telescope in this fashion ensures the safety of the primary mirror while operating the dome shutters. If the mirror cover is closed, this step is not necessary.

  7. Use the manual controls to close both dome shutters. The normal “closed” position for both shutters is near 58 degrees in elevation, or about two-thirds the way up. There is a seam in the tracks next to the dome opening at 58 degrees that provides a reference.


    The manual pushbuttons do not honor any limit switches. Great care must be taken to drive each shutter in the correct direction, and not to drive the shutters against an obstruction.

  8. If the vent doors are open (they typically are not at night), they can also be closed via manual controls near each of the individual vent doors.

  9. Before exiting the dome, re-engage a physical e-stop to ensure the facility remains secure until it can be fully checked over for any inconsistencies.

Shutting down without power

It is not practical (or perhaps not possible) to close the dome shutter without power. In the event that there is no power to the APF dome, it will not be possible to completely protect the facility from inclement weather if the dome shutter is open.

When following this procedure, two able-bodied personnel should be present.

  1. Bring flashlights and a large tarp. There may be an appropriately large tarp stored on the second level by the tool chest.

  2. Engage a physical e-stop upon entering the dome. This will ensure personnel safety if power is suddenly restored.

  3. Take the interior stairwell up to level 2 of the dome, and then to level 3.

  4. Circle around the Levy spectrometer to the opposite side of the third level, between the dome shutter and the telescope.

  5. Once you are standing between the telescope and the shutter, manually pull the telescope down to the horizon, and “pin” the telescope at the horizon. The pin is located on the interior of the elevation yoke nearest the stairwell.


    If the mirror cover is closed, the telescope will be unbalanced, and very bottom-heavy. If released when not pointed at the zenith, the telescope will immediately accelerate due to gravity. There is no mechanical damping, and the telescope could reach unsafe velocities for both personnel and the telescope itself.

  6. Once safely pinned at the horizon, deploy the tarp over the full telescope tube. Secure the tarp as necessary to prevent it from being blown about the dome.