From hdekker@eso.org Thu Aug 23 06:58:02 2007 Date: Thu, 23 Aug 2007 06:57:41 +0200 From: Hans Dekker To: Vik Dhillon Cc: Ivo Saviane , Sandro D'Odorico , gero rupprecht , Andreas Kaufer Subject: Re: New Grism for EFOSC2 Dear Vik, Unfortunately there is not a single provider abe to make the whole device. You need to work with 2 or 3 in several manufacturing/assembly steps which is why February is ambitious but not impossible The recommended provider for the VPHG is Kaiser Optical (KOSI) : http://www.kosi.com/ Contact Jim Arns to get a quotation: arns@KOSI.com. I expect they can deliver in about 3-4 months. They are ONLY capable of manufacturing the plane-parallel VPHG. They usually take care of the plane-parallel BK7 or FuSi plates of the VPHG themselves. A difficulty may be that (if I remember correctly) the EFOSC2 grisms have a circular cross-section. They prefer square or rectangular. This should be clarified with them and the shape may affect the design of the mount and of the prisms. The VPHG has to be glued between two prisms to get a direct-vision device. We have used Halle Nachfl. (Berlin) to do this job but one can also do it yourself. Critical part is the rotational alignment of the VPHG between the prisms. A jig must be prepared to allow the cement to cure in situ in the interferometer (or other alignment device) in the proper orientation. This takes 1 or 2 weeks when done properly (i.e. advance preparation of the curing jig and tools to place the assembly in the test setup). Since H-alpha is the undeviated wavelength, the HeNe wavelength (633 nm) is conveniently close for this test. The prisms can be made by a variety of optical companies and are usually a planning bottleneck due to the sequence of required steps (get quotation-place order / glass procurement / grind-polish / coat) and this takes 3 - 6 months. Try to design with a glass that is on stock at the supplier or at least a standard glass (e.g. one of the Schott preferred glasses). In view of the short timescale I would recommend to contact Halle (D), Winlight and SESO (both F) so at least the steps of prism manufacturing and glueing are in a single hand which saves time. Perhaps there are also suitable companies in GB but we have not recently worked with any. Good luck! Hans Dekker Ivo Saviane wrote: > > Dear all: > > I guess the original suggestion of Andreas was to get the name of a > trusted provider, so that Vik could contact it. In case the provider can > make the VPHG in a short timescale, La Silla can certainly provide the > tech specifications of EFOSC2. > > --- I. > > > Sandro D'Odorico wrote: > > Dear Vik, > > > > Hans and Gero discussed with me your request for helping to procure a > > new EFOSC2 grism. > > Unfortunately we are not really in the best postion to help. EFOSC2 is > > an instrument with which we in Garching had nothing to do for more than > > 15 years. The VPH grisms in the past were procured, I think, > > directly from La Silla, and they must have the mechanical and optical > > specifications. If they have not > > the time to carry out this task in the fast time scale you require, you > > should get from them > > the interface data and place the order directly or through an optical > > group in Europe who e.g. > > is also involved in the science use of the instrument. > > > > best regards, > > Sandro >