| 1. Remove the dewar | See Jon Brinkman or John Briggs for details. |
| 2. Balance the telescope | With the dewar removed, the telescope can be approximately balanced in declination by moving both of the sliding black counterweights all the way down. These weights run along the southwest side of the telescope tube. |
| 3. Lock the axes | Insert the RA and DEC lock pins. The telescope must be accurately at zenith to insert these pins. The RA lock pin is the shorter of the two. |
| 4. Drive power off | Turn off the main power to the telescope servo motors (driver chassis off). |
| 5. Release DEC drives | Disengage the spring pressure on the declination drive roller so the telescope is free to move in declination. Even with the DEC pin in place, there's some slop so by using hand pressure you can confirm the telescope is approximately balanced in declination, at least when it's pointed at zenith. |
| 6. Remove the filter box | As with the dewar, this procedure should be supervised by the Instrument Scientist or the PT Engineer (Brinkman/Briggs). |
| 7. Remove corrector lens | Twelve large cap screws, from the center and back of the mirror cell |
| 8. Remove primary baffle | from the back of the mirror cell (four small cap screws). It's nearly two feet long |
| 9. Remove three large plugs | from the back plate of the telescope. These are three rubber plugs with metal clips that fill the large diameter holes in the primary mirror cell. |
| 10. Move the telescope south | Remove the DEC lock pin while carefully holding onto the telescope and let the telescope swing south to its service position. The lock pin can be inserted when the telescope is at the southern service position, about 7 degrees altitude. The telescope will be top-heavy. Note that when the pin is fully and safely inserted through the drive wheel, you can hear and feel the end of it tap against the inside of a yellow sheet-metal housing. |
| 11. Remove trim weights | Remove any small lead counterweights from the back of the primary mirror cell and note their exact position for later replacement. The position angle of these weights about the optical axis is significant. |
| 12. Attach removal tool | Mount the yellow weldment that serves as a lifting fixture for the mirror cell to the north (top) side of the cell, using four cap screws in the holes marked A,B,C,D. (See page 26 of the PT logbook.) Do not use cap screws that are excessively long, since the holes in the primary cell are not tapped all the way through (to prevent pushing a screw into the primary mirror or its mount). Also note that the weldment has some curvature to it - don't worry about that, since there's no need to flatten it out by excessively tightening the four cap screws. |
| 13. Detach Invar spacers | Remove four 1/4-28 cap screws (see page 26 of the PT logbook) that are at the extreme circumference of the back of the mirror cell. (These screws connect to four Invar rods, internal to the telescope tube.) |
| 14. Install chain hoist |
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| 15. Attach hoist | Connect chain hook to yellow lifting fixture after adjusting hoist so that the hook is in about the right position. Note that one should run the chain loop (which hangs down to the floor) on the east side of the lifting fixture. This keeps the oily chains away from the finder telescope and other vulnerable parts. |
| 16. Tighten the hoist | But not too tight. Make sure it's centered above the load. |
| 17. Detach mirror cell | Remove eight 1/4-28 cap screws that hold the mirror cell to the telescope center section. Adjust chain tension, as required, as you do this. |
| 18. Lower the cell | Lower cell slowly, while pulling it away from the telescope, to the north. The four Invar rods extend about eight inches from the telescope's center section, and the mirror cell must be pulled to the north, to clear these rods, as it is lowered. Try to keep the chain loop from abrading the mirror cell as you lower it. |
| 19. Place it on the floor | Lower cell such that it can be placed mirror-up on
the small white stand. Note that holes in the back of the cell are drilled
such that the stand's three legs can pass up through to contact the glass.
Do not let this happen unexpectedly! Use the stand only to support the
metal back of the mirror cell, not the glass.
The chain should be loose after the cell is supported on the tripod. Disconnect the yellow fixture from the cell, and move it and the hoist assembly off to the side. |
| 20. Remove earthquake restraints | Remove the four triangular mirror "bumpers" from the front inside of the mirror cell. |
| 21. Loosen two transverse supports | Loosen two of the transverse support cylinders using the Allen-head screws centered in the black disks around the outside of the cell. If you loosen only two, say those at the west and north, then the mirror will return to approximate collimation upon reassembly. |
| 22. Remove the mirror | Lift the mirror from the cell and place it on wooden blocks on the floor. This is an easy, one-man lift. I suggest lifting the mirror from the cell by putting one's hands through the mirror's central hole, rather than by placing hands on the outside diameter of the disk, since the clearance is tighter there. |
| 23. Box the mirror | Move the mirror from the blocks into its gray foam-lined plastic storage case. Keep the optical surface up, and do not turn the box over during the move to the Sunspot coating chamber. Cover it with tissue before closing the lid. |
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