From Prime_Optics@bigpond.com Thu Aug 21 13:07:12 2003 Date: Tue, 19 Aug 2003 15:53:21 +1000 From: Damien Jones To: Nigel Douglas Subject: PNS Halpha camera Nigel! >As you have probably heard we are currently gearing up to make the Halpha >camera; Ken is running this from Stromlo, in part because there is a fair >chance the work will be done there, though we have other options such as >Capodimonte, and that of splitting the work up into optical and >mechanical. Anyway, Ken is travelling right now and he asked me to contact >you. Would you be prepared to optimise your camera design for us? Of course! >Here's what has changed: > >1. the camera will work with one filter for continuum imaging and two >filters for narrow-band imaging (ie the continuum filter stays in the >beam). We're still talking 656 +/- 8 nm ? >2. the filters, one of which therefore has to be on a frame that can be >driven out of the beam - John has been working on a design - should as >usual be as small as possible, so the optical design has to offer a >suitable location for them to be placed, allowing for the required >movement of course. They should probably go right in front of the first lens group, in collimated light. Here they will have to be approx 140 mm in diameter. They could go deeper (and get 30% smaller) in the camera but then the range of angles of incidence broadens significantly. >3. we need a fast shutter for this camera; the easiest would be a prontor >type iris shutter but I am not sure about their availability in large >sizes - do you know? anyway this has to be thought about. These beasties are new territory for me. >4. we will probably be using a different detector, and I mention this >because we had problems when we used a different detector in one of the >PN.S arms. Instead of the usual EEV detector we tried a Marconi chip with >exactly the same physical characteristics, and we found the spectrograph >focus to be stigmatic. Now the Marconi lies 1mm further inside the >cryostat than the EEV, according to the ING people. Could this cause a >problem somehow? It seems incredible to me, so I'd like you to see if you >can reproduce the problem with the Zemax set-up for the spectrograph... Classic. You've gone beyond the tolerance on that space between the field flattener and the detector. You'll have to make an adaptor or something to bring that space back to where it should be. This sort of problem would need addressing for the H-alpha detector too. >5. as the TNG has disappeared from view, the camera should be optimised >for the WHT. But having said this, we'd like to be able to switch to a >TNG-optimised design later (I will explain why another time!) - ideally by >shifting a lens/group slightly but more realistically by replacing a lens. We'd change the last group. >Finally, I'd ask you to include the dichroic in the design so that you can >assess the effect on the imagery of large and small-scall departures from >flatness. 2 easy. >If you are available, can you give us a costing and an idea of timescale? yep ... here it is .... (similar to what I sent to Ortwin last year) Item Description Cost(AUD) 1 Startup, re-establish models, evaluate 450.00 2 Re-design with variable back end 2250.00 3 Generate drawings, negotiate with opticians and fit to optical shop 900.00 4 Debug, final as-built fit 900.00 5 Commissioning 900.00 6 TOTAL 5400.00 (no GST if your institute pays, but add 10% if Mt Stromlo does) ... mid-October-ish, prefer later as my diary is chockers! Damien