The Ohio State University College of Mathematical & Physical Sciences Department of Astronomy

Attendees: Jerry Mason, Darren DePoy, Jason Eastman, Ross Zhelem, Ed Teiga, Mark Derwent, Paul Martini, Paul Byard, Dave Stonebreaker, Phil Covington, Bruce Atwood, Andy Krygier, Tom O'Brien, Dan Pappalardo, Jen Marshall, Ray Gonzalez, & Rick Pogge.

Via video from Tucson: Mark Wagner (LBTPO) and Tod Boroson (NOAO/TSIP)

MODS Optics

Ross reported on progress on the MODS large optics. The Blue Corrector lenses are on the path to completion with the first round of Magnetorheological Finishing (MRF) processing currently in progress at QED Technologies in Rochester. The 5th of 6 finishing runs have been completed, the 6th being scheduled for some time tomorrow (May 3). Each run is between 18 and 36 hours, for a total of about 100 hours on the finishing tool. The MRF tool is using a surface map provided by SOML, and attempting to mill the asphere onto the surface with a 2D raster scan. After finishing, it will be shipped back to SOML for further measurement and testing with the holograms.

After some discussion we agreed that we also want SOML to make a coordinate measuring machine (CMM) measurement as well, to help verify that process. Our hope is that only one more MRF iteration will be required.

SOML reports that they have started grinding the first spherical side of the red corrector lens parent and are making good progress.

There is still some discussion about the coatings for the camera primary mirrors and collimators, we should get a report on that soon. The Red and Blue prisms (TIH6 and Fused Silica, respectively) are being fabricated and coated (Al on the Blue, Ag on the Red) by JML at this writing. Finally, we have two competing quotes for the Dichroic coating. This will be a 40-50 layer dielectric coating, with a wide range in price. It looks like we will need another iteration on the coating design before making a final decision.

Open questions remaining on optics are the choice of AGW filters (we need 2 of each for a 4-position filter wheel in the MODS1 and MODS2 AGW units, one of which will be a clear filter), and we need to get a quote for the SDSS filter set for MODS2 (we have the SDSS set for MODS1 in hand).

Gregorian Instrument Rotators

Mark Wagner (LBTPO) reported on progress on the Gregorian Instrument Rotators for LBT. The specification work on the rotators is being done by Sean Callahan at Steward, and is about 80% complete. First priority is being given to the rotators at the LUCIFER focal stations, so the remaining 20% will wait until that is complete. A review will be held after the design is complete. As yet no estimated time to delivery on the design document has been established.