Prime Dark Sites for the "100-club" Telescopes (100-inches to 100m
Class A , Class
B & Class C sites are dark, or fairly
sites where substantial investment has been made or will very soon be
in the construction of substantial, active, professional, ground-based,
optical, research observatories. No man-made light pollution has
yet been detected in broad-band observations near the zenith at Class
and Class "B" sites (see, e.g., Patat, F. 2003, Astronomy and
1183). These dark sites are also where large
telescopes (of equivalent aperture of at least 6.5m) are presently
sited (Class "A") or where construction of such large telescopes has
funded (class "B"). Class "C" sites have either detected light
at the zenith, or are ones where no large telescopes (aperture ~6.5m or
greater) are currently planned. Thus, for example, Cerro Pachon
a "Class A" site; it is still dark at the zenith (the setting zodiacal
light is readily visible over the direction of maximum horizon glow)
and the Gemini South 8m telescope is on
summit. Cerro Tololo, though only a few kilometers away and still
dark, is a "Class C" site,
because no telescopes larger
than the Blanco 4m are currently planned for Cerro Tololo.
A. Sites for telescopes with mirrors already on
aperture >6.5m, undetected light pollution at zenith.
Mauna Kea ( Keck I
2; Subaru; Gemini North. UKIRT
, CFHT , IRTF).
also John MacDonald's excellent web page on the "Light
Environment of Mauna Kea".
(VLT/VLTI, VISTA, VST) This
is in the clearest region of Chile, near the coast (67-68degW,
This area is our Working Group's highest priority for protection
light pollution. Intense
outreach activity (18MB, slow download) by the OPCC
is underway, concentrating initially on Antofagasta and on mines in the
area (particularly PCS Yumbes).
Ferdinando Patat has published an excellent summary of the "Night Sky
Brightness During Sunspot Maximum at Paranal" in the ESO
(No. 115 - March 2004). This provides a
valuable, quantitative benchmark for dark skies work and a
reference point for the protection campaign in Northern Chile over the
next few decades. More details of these measurements at
Paranal are given in Patat, F. 2003a, Astronomy & Astrophysics, 400, 1183.
Information on the algorithm used for his measurements is given in
Patat, F. 2003b, Astronomy & Astrophysics, 401, 797.
Cerro Las Campanas Cerro Las
Campanas (Magellan I & 2,
Cerro Pachon ( Gemini South, SOAR). ( LSST - next
Sutherland Observing Station (10.2m Southern African Large Telescope, SALT).
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West Texas, USA
Mount Locke ( 9.2m
HET , 2.7m Harlan J. Smith telescope). Visit StarDate
Online to get to know an outstanding public outreach and education
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B. Other sites for telescopes being planned or
apertures >6.5m, undetected light pollution at zenith.
de los Muchachos (GranTCan, WHT,
INT, NOT). Visit the OTPC ( english
) or ( spanish
light pollution site, or contact Francisco Javier Diaz-Castro, a member
of this WG. See also the recent paper by M. Pedani on "Light
pollution at the Roque de los Muchachos Observatory".
C. Other major observatory sites with
telescopes having apertures >2.5m & zenith light pollution
than the natural variation in night-sky brightness associated with the
11-year solar cycle.
( 3.9m AAT)
Mount Hopkins ( MMT
Mount Graham (site for
Kitt Peak National Observatory
(Mayall 3.9m, WIYN 3.5m;
see "The Spectrum of the Night Sky over Mount Hopkins and Kitt Peak:
after a decade" - Publications of the Astronomical Society of the
Vol. 112, pp566-573, 2000 - to see a remarkable success story in
controlling light pollution and waste).
Mount Palomar (5m).
(See also the excellent LightLynx
La Silla (ESO
Cerro Tololo (Blanco
4.0m) A movie of Tololo's dark sky is included in Tom Lucas'
production, for "NOVA" on PBS entitled "Runaway
Universe". Cerro Tololo is the most threatened of the major
international observatories in Northern Chile but still has no detected
light pollution at the zenith (the setting zodiacal light is readily
visible over the direction of maximum city glow) - it is, however,
vital that Chilean
continue implementing the massive lighting changes required under
the "Norma Luminica"
DS686 as the nearby communities continue to grow. Action
on lighting changeover is underway in the various
communities and provides a unique opportunity for ground-based and
New Mexico, USA
Apache Point Observatory, APO
3.5m telescope, SDSS telescope)
Alto (3.5m telescope)
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Light pollution is, of course, only one of many criteria that form
the basis for site selection. Other parameters may include
atmospheric turbulence, cloud cover, precipitable water vapour, thermal
emission from the atmosphere, auroral activity, aerosol/dust pollution,
average and maximum wind speeds, seismic activity, rates of snow/rain
fall, accessibility, infrastructure and cost of operation (see, e.g.,
Lawrence et al. 2004, Nature, 431,
Last revised: 17th May, 2006