Re: puzzlin Chandra proposal thread

Hi Saku - 

I reviewed this thread (from Adrienne Juett), but missed that subtle
detail.  I think the thread is conveniently circular, having been
written with the desired answer known.  If it didn't come out the way
you wanted it, you would either have to adjust the exposure time, or
flux and significance.  Does this make sense, or am I missing
something more critical?

--Dave


    Saku> Looking at the Chandra proposal thread:

    Saku> Calculate Exposure Time for a Single Line Detection using ACIS-S/HETG

    Saku> which is at 

    Saku> http://cxc.harvard.edu/proposer/threads/ldet_hetg/index.html


    Saku> At the start of the page it says:

    Saku> ``We would like to determine the exposure time needed to make a 5 sigma 
    Saku> detection of hydrogen-like Ne at 0.9-1.3 keV with a flux of 2.0e-5 photons 
    Saku> cm^-2 s^-1.''

    Saku> They start with a guess of 35ks.  After going through several steps 
    Saku> (a bit more than half way down the page) they say:

    Saku> ``The lowest flux that could be detected is therefore 2.6584e-05 photons cm^-2 
    Saku> s^-1. The chosen 35ks exposure time is adequate to detect the line of 
    Saku> interest.''

    Saku> Is this a misprint?

    Saku> Thanks,
    Saku> Saku 
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