Dear Chandra users,
I have combined the last year's archival dark Moon observations into
the usual canned background event files for chips I2 I3 S2 S3. Their
total exposures are 14-16 ks. While they are on the way to the CALDB,
a preliminary version can be downloaded from
http://cxc.harvard.edu/contrib/maxim/acisbg/data/ (files *darkmoon*).
The observations are cleaned in the usual manner and include only the
periods when a given chip was completely covered by the dark Moon. See
README in that directory for details. A full description will be
posted later, but as was already reported by Biller et al. in January
(http://cxc.harvard.edu/cal, "ACIS", "Background", "Event Histogram
mode"), they are in good agreement with the Event Histogram mode
spectra (obtained with ACIS in the stowed position, not exposed to the
sky), indicating that they give the true ACIS instrumental background.
Let me know of any problems (other than poor statistics -- there are
plans for a longer calibration).
Maxim Markevitch
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