Subject: image quality with new secondary

From: elt@astro.Princeton.EDU

Submitted: Tue, 28 Dec 1999 00:42:39 -0500 (EST)

Message number: 408 (previous: 407, next: 409 up: Index)

The following excerpt from the 12/26/99 3.5m log is worthy of note as
it shows the best image FWHM ever reported for the telescope (previous
best was about 0,7"), presumably due to the replacement of the secondary.

The new secondary was first employed for science observations only on
17 December, and the telescope optical collimation has not yet had its
final fine tuning using the new Shack-Hartmann instrumentation, so there is
no reason to think that these numbers represent the best we will be able
to achieve.  However, they certainly provide strong evidence that the hard
work of many people involved in our image quality campaign and the generous
support of the ARC institutions (the new secondary was the single most
expensive item among the Three Year Plan projects) are paying off in a
major way.

Ed Turner

>The night was clear and warmer than recent weeks, with exceptionally
>good seeing.  Some of the numbers in the focus log below are actually
>an overestimate of the seeing, since we were undersampled with GRIM at
>f/5.  The telescope was getting considerably better seeing (at least
>in the infrared) than the DIMM monitor.
>
>...
>
>                                FOCUS LOG
>                             DECEMBER 26 1999
>                                                 Wind
>Time   Inst        Focus     Az  El   #Temp    Dir  MPH  filt  FWHM "
>17:35  GrIm2      0(1016)   119  45  0.6/3.3   152   11   J     1.1
>19:05  GrIm2      0(846)    147  59  1.2/1.0   177   10   J     0.76
>23:15  GrIm2    +50(855)    253  74  1.6/1.1   226    9   K     0.52
>01:35 GRIM(f/10) +10(789)   191  77  1.7/1.1   276   10   H     0.57
>02:20 GRIM(f/5)  -50(838)   194  46  1.0/0.7   293   11   J     0.84 
>#First temp is air, second temp is telescope.

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