Re: cluster obs requirements

From: Henk Hoekstra (hoekstra@uvic.ca)
Date: Fri Jan 27 2006 - 12:04:24 PST

  • Next message: Marc Postman: "Re: cluster obs requirements"

    Hi Marc, I agree that should be clarified, but the
    exposure times are 3:1 but the F850LP are 4 slightly shorter exposures.
    They want 4 to avoid CRs.

    Cheers,
    Henk

    On Fri, Jan 27, 2006 at 03:02:00PM -0500, Marc Postman wrote:
    > OK then we should correct the proposal text on page 6 which currently
    > states:
    >
    > (each orbit contains four ACS/F850LP dithered cosmic-ray splits plus
    > one ACS/F775W exposure)---
    >
    > That looks like 4:1 to me. So the four in the above sentence should be
    > three! Good catch!
    >
    > Marc
    >
    > On Jan 27, 2006, at 2:54 PM, marek kowalski wrote:
    >
    > >Hello Marc,
    > >
    > >I just want to make sure we phrase it consistently. In the SNe
    > >observing requirement section we say 515 seconds exposure in I and
    > >340 seconds in the four z-band exposures. That makes a ratio of
    > >1:2.64. The waek lensing section says 25% to 75% which is close enough
    > >to this ratio but different from 4:1.
    > >
    > >Cheers,
    > >
    > >Marek
    > >On Jan 27, 2006, at 11:43 AM, Marc Postman wrote:
    > >
    > >>Here are our expected photometric errors in i775 and z850 - as Henk
    > >>knew, the 4:1 exposure ratio for z850:i775 yields comparable errors at
    > >>each AB mag interval. these are based on scaling our Lynx (z=1.27)
    > >>mosaic exposures to the exptimes we will have in our co-added data. I
    > >>am modifying the cluster obs reqs section accordingly and making the
    > >>CMR slope/scatter measurements the main drivers.
    > >>
    > >><SNeHST_photerr_vs_mag.eps>
    > >>On Jan 27, 2006, at 2:07 PM, Saul Perlmutter wrote:
    > >>
    > >>>...and of course, show that our new F775 exposures (515 sec times ~7
    > >>>or 8 orbits co-added) is exactly what we need!
    > >>>
    > >>-----------------------------------------------------------------
    > >>Marc Postman Email: postman@stsci.edu
    > >>STScI - CMO Phone: +1-410-338-4340
    > >>3700 San Martin Drive Fax: +1-410-338-4424
    > >>Baltimore, MD 21218 U.S.A. http://www.stsci.edu/~postman
    > >>
    > >>
    > >
    > >--------------------------------------------------------------
    > >Marek Kowalski Lawrence Berkeley National Laboratory
    > >mpkowalski@lbl.gov 1 Cyclotron Road, MS 50R5008
    > >(510) 486 4652 Berkeley, CA 94720-8160
    > >--------------------------------------------------------------
    > >
    > >
    > -----------------------------------------------------------------
    > Marc Postman Email: postman@stsci.edu
    > STScI - CMO Phone: +1-410-338-4340
    > 3700 San Martin Drive Fax: +1-410-338-4424
    > Baltimore, MD 21218 U.S.A. http://www.stsci.edu/~postman

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