Subject: Re: Tony Tyson, on figures of merit

From: Nick Kaiser

Submitted: Fri, 11 Jun 2004 19:56:38 -1000 (HST)

Message number: 238 (previous: 237, next: 240 up: Index)

>
> 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?

That's the planned exposure time for the solar system and redder
passbands.  Exposure times for g, r will be somewhat longer to avoid any
performance hit from read noise.

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

The outer primary diameter is 1.8m, and in the current design the
secondary + support obscures about 36% of this.  That gives an effective
clear diameter of 1.44m.

Cheers,
Nick




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