The ReSTAR Report and Telescope Size
Astro...@gmail.com
carefully, because I am interested in the role of "smaller"
telescopes.
I found the report (and minutes) interesting and valuable,
but I was struck by one thing:
The minutes discuss particular research programs
in terms of telescope aperture, thus:
"Galactic superwinds can be studied with 0.9 meter
telescopes ..."
"star formation processes in nearby galaxies will
require 2-4 meter telescopes for imaging ..."
The only nod that I found toward trading off etendu for
time occurs with reference to detector area, not aperture:
"It might be more cost effective to use more nights
with a smaller FOV than to built an instrument with
this large FOV."
The report writers characterize programs by aperture,
although photon collection is related to collecting-area x time,
and I believe that, for much optical imaging and photometry,
aperture can be traded off against mirror-count and/or duration.
Put more bluntly: Most of what ReSTAR calls "two meter telescope
work" could be equally well performed by 4 x one-meter telescopes,
but this is (in effect) denied by the wording of the minutes and
report.
Did you notice this too? Are you bothered/intrigued by it?
I am interested in corresponding with astronomers who would
like to explore the merits and limitations of claims like
Four one-meter telescopes in parallel, or one one-meter
telescope with 4 x the time allocation, equals a two meter
telescope. (And cost less.)
Sixteen half-meter telescopes in parallel, or one half-meter
telescope with 16 x the time allocation, equals a two meter
telescope. (And cost less.)
and how they might change the way that "research telescope" is
defined and how research telescopes are created and used.
Bob Ayers
astro...@gmail.com
www.RobertMartinAyers.org <= a bit about me and my "sciences fund"
Steve Willner
> The report writers characterize programs by aperture,
> although photon collection is related to collecting-area x time,
> and I believe that, for much optical imaging and photometry,
> aperture can be traded off against mirror-count and/or duration.
This is a complex subject, and a lot depends on exactly what
observation one wants to do. Some of the factors that drive one
towards large telescopes are that neither instruments nor operating
costs are free. It often doesn't make sense to put an expensive
instrument on a small telescope, nor is it feasible to schedule 1000
nights even on a small telescope. On the other hand, there are
indeed projects that can be done perfectly well on small telescopes;
the "coude' feed" at KPNO is a classic example.
I don't know what the ReSTAR report is, but my guess is that the
authors were putting in some unstated but generally accurate
assumptions about the types of observations needed and likely costs
of different ways to do them. Of course they may have made errors,
but it will take an examination of the details to show whether or not
that's so.
--
Steve Willner Phone 617-495-7123 swil...@cfa.harvard.edu
Cambridge, MA 02138 USA
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