Chris,
Temperature variations are rare though, and the biggest contribution
I have found in the time of the night (distance in time from sunset,
again a direct link to excitation effect of the atmosphere.
2 months is about my timescale also - let's work on this together
with some full data sets!
Jean-Charles.
>
> > ... And now
> > that flats are (presumed) final, a focus on the defringing recipe is needed
> > as well.
>
> Forgot to comment on this ... As you know, I was trying in December
> to come up with some better procedure for defringing. There is some
> tentative evidence that fringing is improved when you defringe with
> fringes of about the same amplitude in DU/s (after allowing for airmass
> effects). This is maybe not surprising: night sky level is an excita-
> tion effect, and excitation affects the relative strengths of lines
> in the airglow.
>
> However by far the biggest effect I found was that the really gross
> defringing problems happen when the mosaic is not at the proper
> temperature. This was quite striking.
>
> I'm afraid I won't have a chance to work on this further for a
> month or two.
>
> -----------------------------------------------------------------
> Chris Pritchet pritchet at uvic.ca
> Dept of Physics & Astronomy http://www.astro.uvic.ca/~pritchet
> University of Victoria
> P.O. Box 3055 250-721-7744 (office)
> Victoria, BC V8W 3P6 250-884-5047 (cell)
> CANADA 250-721-7715 (FAX)
> -----------------------------------------------------------------
Received on Fri Feb 15 2008 - 16:34:46 HST