To all 3.5-m users: Most of you know that the enclosure (aka "dome") wheels for the 3.5-m are cracked and getting worse to the point that we fear that a wheel will start spalling, leaving chunks on the rail and causing significant damage. This could happen at any time and would necessitate closing the telescope until repairs are made. We are monitoring the cracks with frequent wheel inspections and limiting the use of azimuthal slews. An attempt to repair the worst wheel (of 4) in place was made in November but was ineffective because of unexpectedly high forces needed to remove the wheel shaft from its bearings. A new plan which involves removing the entire wheel assembly is being devised and will be implemented by L&F engineer Terry King. Terry was at the site yesterday and today to assess their plan, and feels that the single wheel repair could be accomplished during or around the scheduled 3.5-m shutdown 29 January through 4 February. The actual start and finish dates are not certain at this time, and may require pre-empting scheduled science programs. Repairing the other 3 wheels would be done at a later time because parts with long lead-times would need to be fabricated. More will be posted when available. It is also our decision based on several recommendations (including Terry's), that we will continue telescope operation until the shutdown, provided the wheels remain intact. Our thanks also to Patrick Waddell and the engineering group at UWashington for their advice and help in getting L&F to respond quickly to our difficulty. Bruce Gillespie APO APO APO APO APO Apache Point Observatory 3.5m APO APO APO APO APO This is message 41 in the apo35-general archive. You can find APO the archive on http://astro.princeton.edu:82/apo35-general/INDEX.html APO To join/leave the list, send mail to apo35-request@astro.princeton.edu APO To post a message, mail it to apo35-general@astro.princeton.edu APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO