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

Attendees: Darren DePoy, Jerry Mason, Jen Marshall, Pat Osmer, Mark Derwent, Chris Morgan, Tom O'Brien, Paul Byard, Dan Pappalardo, Bruce Atwood, and Rick Pogge.

Optics

Paul Byard has received acceptance testing documents from REOSC for the first 2 (of 4) collimator mirrors. In summary:

1. The measured wavefront meets specification, but
2. There are small departures at the edges.

PostScript: We learned that there are no problems with cracks in the mirror, and subsequent analysis shows that despite the slight systematic departures at the edges, the collimators will more than satisfy our specifications. Our concern was not so much with the impact on the optical quality (it is very small), rather in that it might be a sign of structural problems. This turned out, to our great relief, not to be the case. The parts have now been accepted and shipped.

Three request-for-quote (RFQ) documents have been sent to possible vendors for reflective and anti-reflection coatings for the MODS optics. This exploratory RFQ is meant to (a) give us some idea of what it would cost and (b) find out what vendors can and cannot do. Key parameters we have requested in these exploratory RFQs are:

1. Low Temperature during coating, T<50° C.
2. Protected Silver for the Red channel collimators and camera primaries
3. Enhanced Aluminum for the Blue channel collimators and camera primaries
4. MgF₂ AR coatings for the camera correctors, field flatteners, and field lens.

Mechanical Design

With most of the shop working on the LBT Aluminizing system, only Mark Derwent is taking care of remaining mechanical design issues.

1. The instrument hatch (aka "dark slide") mechanism has been designed and Mark is working up a parts list for purchased components.
2. Mark is continuing to work with Indian Creek on the drawings for the welding fixture that will be used to assemble the upper structures.