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
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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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<HTML><HEAD>
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<BODY bgColor=3D#ffffff>
<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> </DIV>
<DIV>Current DIS users should be aware that this upgrade will have the =
following=20
effects on the data format.</DIV>
<DIV> </DIV>
<DIV>1) The pixel scales will change from the current value of=20
~0.54"/pixel (both red and blue sides) to 0.40"/pixel for the red =
camera=20
and to 0.42"/pixel for the blue camera. Note that the new optics =
will NOT=20
change the total field of views for either side of the =
spectrograph. 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. With the new camera optics, =
spectra=20
will be spread across the entire length and width of the =
detectors.</DIV>
<DIV> </DIV>
<DIV>2) The vignetting of the current cameras will be =
eliminated. =20
This vignetting has no impact on the imaging mode, but seriously impairs =
spectroscopic measurements. The new cameras will afford the =
following=20
dispersions and bandpasses:</DIV>
<DIV> </DIV>
<DIV><STRONG>Red Camera =
=20
=20
Dispersion Bandpass</STRONG></DIV>
<DIV><STRONG>Low dispersion grating:</STRONG> 330.83=20
A/mm 5650* A</DIV>
<DIV><STRONG>Med. dispersion grating: =20
</STRONG>159.82 =20
4100 </DIV>
<DIV><STRONG>High dispersion grating: =20
</STRONG>51.46  =
; 1370</DIV>
<DIV> </DIV>
<DIV><STRONG>Blue Camera</STRONG></DIV>
<DIV><STRONG>Low dispersion grating: =20
</STRONG>172.46 =20
1900*</DIV>
<DIV><STRONG>Med. dispersion grating: =20
</STRONG>83.66  =
; 1900*</DIV>
<DIV><STRONG>High dispersion grating: =20
</STRONG>38.60  =
; 1010 </DIV>
<DIV> </DIV>
<DIV>*These bandpasses are determined by the atmospheric and dichroic =
cutoffs=20
rather than by the detector.</DIV>
<DIV> </DIV>
<DIV> The new blue camera optics MAY have an impact on =
the=20
throughput of the bluest wavelengths accessible with DIS. The =
current=20
blue camera optics show transmission curves which are above 90%=20
at wavelengths greater than 3500 A. Thus, it is possible =
that=20
the blue response of the spectrograph will be considerably enhanced =
between=20
3500 and 4000 A. However, users should be aware that even after =
this=20
upgrade there will be one optical element near the front of the=20
spectrograph which will still have the original multi-layer =
coating. 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. =
This=20
problem will then have to be addressed at a later time.</DIV>
<DIV> </DIV>
<DIV>Also note that as of a few weeks ago, the new parallel read-out =
boards were=20
successfully installed in the spectrograph. Both cameras now =
read-out=20
simultaneously without noise problems. This results in a =
substantial=20
savings of time for most observations. </DIV>
<DIV> </DIV>
<DIV>We all have Peter Doherty and Craig Loomis to thank for that =
work. =20
</DIV>
<DIV> </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> </DIV>
<DIV>We thank you for your patience. Hopefully by the last week in =
January=20
we will have good news to report on the DIS optics upgrade!</DIV>
<DIV> </DIV>
<DIV>Jeff Morgan</DIV>
<DIV>UW Astronomy<BR>Box 351580<BR>Seattle, WA 98195 (206)=20
543-6182</DIV></BODY></HTML>
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