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Space Telescope Imaging Spectrograph
STAN - July 1999

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| HST Spectroscopy                      STIS/GHRS/FOS |
| STScI Analysis Newsletter                 July 1999 |
|                                                     |
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New HST Spectroscopy STAN Format & Content
    
We are continuing a transition to a new format for 
the HST Spectroscopy STAN.  At the top, an index of 
topics is listed with the web address where you can go 
to get all of the details.  Below this, short summaries 
are provided for each topic. And as always, the STAN 
will be posted on the STIS web site, where all of these 
topics will be hypertext links directing you to the 
full writeup.  All items appearing here and more are 
posted on the STIS web site, but we will only highlight 
items of particular interest or importance in the STAN.
    

CCD Bias and Dark Reference Files


Improved features in the New ETCs
 

Throughput Changes


G430M Focus Gradient Detected


STIS Cycle 9 Instrument Handbook 


STIS Web Site Updates

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CCD Bias and Dark Reference Files

The procedure for the production of STIS CCD bias 
reference files has recently been changed.  This change 
was prompted by the observation that hot columns in CCD 
data are often not well eliminated in the pipeline 
reduction.  Recently, the hot column residuals have been 
becoming more apparent due to the increasing number of 
charge traps. Especially short exposures have been 
suffering from residual hot columns.  
 

Improved features in the New ETCs

The STIS Exposure Time Calculators have been 
re-engineered, and they were made available on 4 August 
1999 to help GOs prepare their Phase 1 proposals for 
Cycle 9.  These ETCs offer a number of new features, 
which are described in the on-line help documentation. 
    

Throughput Changes in Synphot

The synphot throughput files for all the gratings have 
now been updated.  The changes are most significant 
(>7%) for the Echelle-modes, and for G230MB longward 
of 2200A.


G430M Focus Gradient Detected
 
A time variation has been detected in the cross-
dispersion width of spectra which exhibit a strong 
wavelength dependence.  The strongly increasing width
with time, and with a strong dependence on dispersion 
position is thought to arise from two factors:  (1) over 
this interval the telescope breathing was monotonic and 
about a factor of two larger than typical values, and 
(2) the G430M mode has an intrinsic focus gradient.  The 
G430M appears to have some power or astigmatism which 
produces the observed focus gradient. 
    

STIS Cycle 9 Instrument Handbook

The Cycle 9 STIS Instrument Handbook is now available 
online in a variety of formats: One large PDF file,
smaller PDF files broken into chapters for faster
loading, and HTML.


STIS Web Site Updates

We are in the process of updating the STIS Web 
Site in preparation for Cycle 9.  There are
many changes, updates, and additions, and more on
the way.  Most importantly for proposers, the
new Instrument Handbook,  Phase I proposal 
instructions, and the new ETCs are now available.


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List of Recent Preprints Now on Line
    
 The list of preprints based on HST spectrographs data
 that user to occupy this space is now available at 
 http://www.stsci.edu/science/preprints/ for easy browsing.
    
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