Subject: Fwd: Returned mail: see transcript for details

From: Donald G. York

Submitted: Thu, 27 Jun 2002 22:38:14 -0500

Message number: 595 (previous: 594, next: 596 up: Index)

>
>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

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