> >Date: Thu, 27 Jun 2002 22:23:11 -0500 >To: apo35-general@astro.princton.edu >From: "Donald G. York" <don@oddjob.uchicago.edu> >Subject: scattered light in the echelle >Content-Type: text/plain; charset="us-ascii" ; format="flowed" > > There has been concern and considerable thought concerning the >orgin of scattered light that appeared in the >> spectrograph, between the orders, during an accidental warmup in June >> 2002. >> No specific cause has been identified, after hours and hours of work >> by a large team. We are planning to do nothing at the moment, until >> at least July 15, when the summer shutdown occurs and the telescope >> optics is recoated. >> >> For upcoming observing, be aware that the psf may be different (two >> Gaussians, one broad, rather than one). And, if the scattering is >> small angle in nature, there could be increased crosstalk between the >> orders. Julie and I advise that untrailed exposures are least >> susceptible to yielding problems. WE have an excellent test for cross >> talk. Where the orders are closest together, the spectrum is full of >> very strong, telluric, absorption lines. Julie made plots of orders >> adjacent to those with strong telluric lines (see in almost final >> version of SPIE paper, attached), based on pre-June 2002 spectra. The >> post-event spectra have now been similarly examined and no cross talk >> can be detected. Prudence suggests, however, that we assume some >> small angle scattering and do not trail. >-- >Dr. Donald G. York >Horace B. Horton Professor of Astronomy and Astrophysics -- Dr. Donald G. York Horace B. Horton Professor of Astronomy and Astrophysics APO APO APO APO APO Apache Point Observatory 3.5m APO APO APO APO APO This is message 595 in the apo35-general archive. You can find APO the archive on http://www.astro.princeton.edu/APO/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