These files have 5 plots.  The 1st plot is the resulting effective area
curve (spectrograph efficiency) obtained from observations of BD+28
4211 (an sO subdwarf) acquired on 2006-07-01T07:50:25.217 with the new
B400 and R300 gratings in DIS on the 3.5m at APO by observers Stephan
McCandliss and Roxana Lupu working on Q2JH08.  The observing specialist
was Jack Dembicky.  I believe this was the first observation using the
new R300 grating.

The other 4 plots show the calibration chain (in a rather pedantic
fashion) starting from the extracted DN per sec per pixel (plot 2) -->
e- per sec per Ang (plot 3) --> erg per sec per Ang (plot 4) and the
absolute stellar flux of BD+28 4211 as obtained from
http://www.stsci.edu/hst/observatory/cdbs/calspec.html (plot 5).  Plot
1 is the result of dividing (plot 2) by (plot 5).

The seeing was  1.2''.  The sky was clear. The large 5'' slit was used.
Subsequent observations with the 0.9'' slit have about 1/2 the counts.
Corrections have not been made for airmass.  The red band fringing has
not been removed and neither has the sky background (although this
signal is small compared to the fringing amplitude).  The O2
atmospheric absorption bands can be seen clearly at 6900 and 7600 Ang.

The effective area can be used by observers to estimate the countrate
per pixel for each individual channel provided the source flux is
known.

Send questions and comments to stephan@pha.jhu.edu; clear skys...

:Stephan R. McCandliss, Principal Research Scientist -- JHU 07-18-2006