Subject: Tony Tyson, on figures of merit

From: Michael Strauss

Submitted: Fri, 11 Jun 2004 11:59:19 -0400

Message number: 235 (previous: 234, next: 236 up: Index)

 > 
 > I agree with all of Gary's points regarding the new parameters table.
 > But it addresses only one category of science an LSST could undertake.
 > Some science drivers don't need IR, some are more sensitive to surface
 > brightness, and others are very sensitive to the exposure time.  I
 > suggest modifying SNAP either into two columns with Optical and IR
 > explicitly listed or at least say for example 0.34 + 0.34 etc if one
 > column.  We should be listing three figures of merit, and explain them
 > as we now do in the caption: etendue, etendue/arcsec^2 (as now), and
 > etendue/(arcsec^2 * exposure time).  The exposure time could be either
 > what is currently planned or the time to reach the sky limit.
 > Finally, we should be using effective aperture (including secondary
 > obscuration) for each facility.

The whole issue of figures of merit, and which are the appropriate
ones, is a rather involved one.  My suggestion is that we remove the
current FOM line from the table (rather than adding several others),
and adding lines for etendue and for suggested exposure time.  

For Pan-STARRS, I am quoting 

http://pan-starrs.ifa.hawaii.edu/public/widefield/survey_strategies.html

for a ~30 second exposure time (depending on filter).  Correct? 

Also, Nick, what is the effective aperture (including obscuration) of
the Pan-STARRS telescope?  Is it indeed 1.8m? 

				 Thanks,  Michael

LSST LSST LSST LSST LSST    Mailing List Server   LSST LSST LSST LSST LSST LSST
LSST
LSST  This is message 235 in the lsst-general archive, URL
LSST         http://www.astro.princeton.edu/~dss/LSST/lsst-general/msg.235.html
LSST         http://www.astro.princeton.edu/cgi-bin/LSSTmailinglists.pl/show_subscription?list=lsst-general
LSST  The index is at http://www.astro.princeton.edu/~dss/LSST/lsst-general/INDEX.html
LSST  To join/leave the list, send mail to lsst-request@astro.princeton.edu
LSST  To post a message, mail it to lsst-general@astro.princeton.edu
LSST
LSST LSST LSST LSST LSST LSST LSST LSST LSST LSST LSST LSST LSST LSST LSST LSST