Subject: DIS optics upgrade, coming soon to a spectrograph near you!

From: Jeff Morgan

Submitted: Thu, 19 Dec 2002 15:10:53 -0800

Message number: 642 (previous: 641, next: 643 up: Index)

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We would like to inform the general community of DIS users that the =
upgrade of the camera optics is currently scheduled to take place during =
the week starting 13 Jan 2003.

Current DIS users should be aware that this upgrade will have the =
following effects on the data format.

1)  The pixel scales will change from the current value of ~0.54"/pixel =
(both red and blue sides) to 0.40"/pixel for the red camera and to =
0.42"/pixel for the blue camera.  Note that the new optics will NOT =
change the total field of views for either side of the spectrograph.  =
For the imaging mode you will still have a 6'x4' FOV and for the =
spectroscopic mode you will still have a 6' long slit.  With the new =
camera optics, spectra will be spread across the entire length and width =
of the detectors.

2)  The vignetting of the current cameras will be eliminated.  This =
vignetting has no impact on the imaging mode, but seriously impairs =
spectroscopic measurements.  The new cameras will afford the following =
dispersions and bandpasses:

Red Camera                        Dispersion        Bandpass
Low dispersion grating:    330.83 A/mm    5650* A
Med. dispersion grating:    159.82                4100=20
High dispersion grating:    51.46                   1370

Blue Camera
Low dispersion grating:    172.46                1900*
Med. dispersion grating:    83.66                 1900*
High dispersion grating:    38.60                 1010 =20

*These bandpasses are determined by the atmospheric and dichroic cutoffs =
rather than by the detector.

   The new blue camera optics MAY have an impact on the throughput of =
the bluest wavelengths accessible with DIS.  The current blue camera =
optics show transmission curves which are above 90% at wavelengths =
greater than 3500 A.  Thus, it is possible that the blue response of the =
spectrograph will be considerably enhanced between 3500 and 4000 A.  =
However, users should be aware that even after this upgrade there will =
be one optical element near the front of the spectrograph which will =
still have the original multi-layer coating.  If the attenuation of this =
single surface at these wavelengths is strong enough, then the new =
optics will not help the blue throughput problem.  This problem will =
then have to be addressed at a later time.

Also note that as of a few weeks ago, the new parallel read-out boards =
were successfully installed in the spectrograph.  Both cameras now =
read-out simultaneously without noise problems.  This results in a =
substantial savings of time for most observations. =20

We all have Peter Doherty and Craig Loomis to thank for that work. =20

At the same time that the new optics are installed we will also be =
installing a new pre-amp board into the red camera in an effort to =
eliminate the 120 Hz noise spikes that are currently present in that =
detector.

We thank you for your patience.  Hopefully by the last week in January =
we will have good news to report on the DIS optics upgrade!

Jeff Morgan
UW Astronomy
Box 351580
Seattle, WA 98195  (206) 543-6182
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<DIV>We would like to inform the general community of DIS users that the =
upgrade=20
of the camera optics is currently scheduled to take place during the =
week=20
starting 13 Jan 2003.</DIV>
<DIV>&nbsp;</DIV>
<DIV>Current DIS users should be aware that this upgrade will have the =
following=20
effects on the data format.</DIV>
<DIV>&nbsp;</DIV>
<DIV>1)&nbsp; The pixel scales will change from the current value of=20
~0.54"/pixel (both red and blue sides)&nbsp;to 0.40"/pixel for the red =
camera=20
and to 0.42"/pixel for the blue camera.&nbsp; Note that the new optics =
will NOT=20
change the total field of views for either side of the =
spectrograph.&nbsp; For=20
the imaging mode you will still have a 6'x4' FOV and for the =
spectroscopic mode=20
you will still have a 6' long slit.&nbsp; With the new camera optics, =
spectra=20
will be spread across the entire length and width of the =
detectors.</DIV>
<DIV>&nbsp;</DIV>
<DIV>2)&nbsp; The vignetting of the current cameras will be =
eliminated.&nbsp;=20
This vignetting has no impact on the imaging mode, but seriously impairs =

spectroscopic measurements.&nbsp; The new cameras will afford the =
following=20
dispersions and bandpasses:</DIV>
<DIV>&nbsp;</DIV>
<DIV><STRONG>Red Camera&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; =
&nbsp;&nbsp;&nbsp;=20
&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;=20
Dispersion&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; Bandpass</STRONG></DIV>
<DIV><STRONG>Low dispersion grating:</STRONG>&nbsp;&nbsp;&nbsp; 330.83=20
A/mm&nbsp;&nbsp;&nbsp; 5650* A</DIV>
<DIV><STRONG>Med. dispersion grating:&nbsp;&nbsp;&nbsp;=20
</STRONG>159.82&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;=20
&nbsp;&nbsp;&nbsp; 4100 </DIV>
<DIV><STRONG>High dispersion grating:&nbsp;&nbsp;&nbsp;=20
</STRONG>51.46&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp=
;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1370</DIV>
<DIV>&nbsp;</DIV>
<DIV><STRONG>Blue Camera</STRONG></DIV>
<DIV><STRONG>Low dispersion grating:&nbsp;&nbsp;&nbsp;=20
</STRONG>172.46&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;=20
&nbsp;&nbsp;&nbsp; 1900*</DIV>
<DIV><STRONG>Med.&nbsp;dispersion grating:&nbsp;&nbsp;&nbsp;=20
</STRONG>83.66&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp=
;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1900*</DIV>
<DIV><STRONG>High dispersion grating:&nbsp;&nbsp;&nbsp;=20
</STRONG>38.60&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp=
;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1010&nbsp;&nbsp;</DIV>
<DIV>&nbsp;</DIV>
<DIV>*These bandpasses are determined by the atmospheric and dichroic =
cutoffs=20
rather than by the detector.</DIV>
<DIV>&nbsp;</DIV>
<DIV>&nbsp;&nbsp;&nbsp;The new blue camera optics MAY have an impact on =
the=20
throughput&nbsp;of the bluest wavelengths accessible with DIS.&nbsp; The =
current=20
blue camera optics show transmission curves which are above 90%=20
at&nbsp;wavelengths greater than&nbsp;3500 A.&nbsp; Thus, it is possible =
that=20
the blue response of the spectrograph&nbsp;will be considerably enhanced =
between=20
3500 and 4000 A.&nbsp; However, users should be aware that even after =
this=20
upgrade there&nbsp;will be one optical element near the front of the=20
spectrograph which will still have the original multi-layer =
coating.&nbsp; If=20
the attenuation of this single surface at these wavelengths is strong =
enough,=20
then the new optics will not help the blue throughput problem.&nbsp; =
This=20
problem will then have to be addressed at a later time.</DIV>
<DIV>&nbsp;</DIV>
<DIV>Also note that as of a few weeks ago, the new parallel read-out =
boards were=20
successfully installed in the spectrograph.&nbsp; Both cameras now =
read-out=20
simultaneously without noise problems.&nbsp; This results in a =
substantial=20
savings of time for most observations.&nbsp; </DIV>
<DIV>&nbsp;</DIV>
<DIV>We all have Peter Doherty and Craig Loomis to thank for that =
work.&nbsp;=20
</DIV>
<DIV>&nbsp;</DIV>
<DIV>At the same time that the new optics are installed we will also be=20
installing a new pre-amp board into the red camera in an effort to =
eliminate the=20
120 Hz noise spikes that are currently present in that detector.</DIV>
<DIV>&nbsp;</DIV>
<DIV>We thank you for your patience.&nbsp; Hopefully by the last week in =
January=20
we will have good news to report on the DIS optics upgrade!</DIV>
<DIV>&nbsp;</DIV>
<DIV>Jeff Morgan</DIV>
<DIV>UW Astronomy<BR>Box 351580<BR>Seattle, WA 98195&nbsp; (206)=20
543-6182</DIV></BODY></HTML>

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