Oct 6, 2026: Recovering from an emergency stop on the 12-inch

Michael Richmond
Nov 6, 2026

During one of our introductory astronomy lab classes, the telescope started moving in a dangerous direction, so the operator pressed the "Emergency Stop" button (press and hold "Mode"). After that, the telescope was turned off, the dome was closed, and things were left as-is. If one tries to turn on the telescope in the usual manner, the control system will force a new polar alignment, which isn't so easy to perform.

So, on Oct 6, I arrived in the early evening to put the telescope back in order. The text below is copied from my notes as I went through the procedure; perhaps it will be useful to someone (myself, likely) in the future. The entire set of operations took roughly one hour.

  1. Remove all cables from the back of the tube, so it can swing and rotate freely
  2. Turn on power. Hand paddle displays message "Press 0 to align or MODE for menu".
  3. Press "0" to start alignment process.
  4. Enter Daylight Saving, Time, Date. Hand Paddle now displays message "Polar Align .... " with lots of text which scrolls past very quickly.
  5. Move telescope using arrow buttons so that it points to the NCP (as determined roughly using setting circles on mount)
  6. Press "Enter"
  7. Scope rotates by about 90 degrees to West. The control system thinks it is now pointed to Polaris. I didn't bother to look to check.
  8. After making no adjustments, Press "Enter". The control system thinks that I've centered Polaris.
  9. Scope automatically slews to a bright star -- this time, it chose Capella. I couldn't see Capella in the finder or main telescope, due to clouds.
  10. Despite not being able to confirm that the chosen star was centered, I pressed "Enter".
  11. Scope declares "Successful Alignment."

Now, if the weather had been good, and I had been able to center Capella after step 9, then the job would be pretty much completed; I'd simply define a new Park Position and turn off. But in this case, I needed to make further checks.

  1. Tell scope to slew to Jupiter, which was in a clear region of the sky.
  2. Scope moves to the correct-ish Declination, but is off in RA by about 1 hour to the East.
  3. Find and center Jupiter in the telescope.
  4. Tell the telescope to "Sync" on Jupiter.
  5. Issue "Park Scope" command.
  6. Scope moves to about 1 hour West of regular Park Position.
  7. Turn off power.

I was suspicious at this point that more than just the Park Position might be offset, so I continued.

  1. Turn on power
  2. Enter Daylight Saving, Time, Date.
  3. Issue "Goto Jupiter" command.
  4. Scope moves to correct Declination, but is offset in RA by about 1 hour to West.
  5. Move manually to Jupiter using arrow buttons and center it.
  6. Issue "Sync Scope" command.
  7. Move manually to a proper parking position.
  8. Issue "Set Park Position" command. After it completes, slew just a bit in RA to move scope away from this position, so I'll know if it returns properly.
  9. Issue "Park Scope" command. At this point, scope does return to the proper park position.
  10. Turn off power.

The real work is complete at this point. Because I was paranoid, I went through the cycle one more time to see if it would properly move to Jupiter when requested.

  1. Turn on power.
  2. Enter Daylight Saving, Time, Date.
  3. Issue "Goto Jupiter" command.
  4. Telescope does slew to Jupiter, to within 1 degree or so. Hooray!
  5. Center Jupiter manually.
  6. Issue "Sync Scope" command.
  7. Issue "Park Scope" command. Scope does move to the proper park position.
  8. Turn off power.
  9. Replace all cabling on the back of the telescope tube.