Measuring and Modelling Rural skyglow Photometry of skyglow in rural areas:- Introduction: The...
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Measuring and Modelling Rural skyglow Photometry of skyglow in rural areas:- Introduction: The current situation in the UK and the problem of low angle unshielded illumination. 1, Some luminance profiles from rural locations. 2, Modelling luminaires, scatter, and skyglow C J Baddiley British Astronomical Association Campaign for Dark Skies.
Measuring and Modelling Rural skyglow Photometry of skyglow in rural areas:- Introduction: The current situation in the UK and the problem of low angle
Measuring and Modelling Rural skyglow Photometry of skyglow in
rural areas:- Introduction: The current situation in the UK and the
problem of low angle unshielded illumination. 1, Some luminance
profiles from rural locations. 2, Modelling luminaires, scatter,
and skyglow C J Baddiley British Astronomical Association Campaign
for Dark Skies.
Slide 2
NOAA CPRE UK changes Map NOAA UK isophotic data for 1993 and
2000 Black 0-1.7..can see MW when clear, Blue 1.7-50 MW visible
occasionally, light blue 50-150 can see MW very occasionally,
yellow 150-240.. And above..never see the Milky Way, Red...
instrument saturation 24-255. The increase in the ambient lighting
at the second isophot level in just 7 years is alarming. (NOAA/
CPRE) NOAA data UK light pollution increase from 1993 to 2000
Slide 3
Europe prediction from DMSP data Atmospheric light pollution
Europe now and prediction for 2025 Computer modelled atmospheric
skyglow isophotes for Europe, Left 1995.Right prediction for 2025
From a few stars only visible (red) to a few hundred (yellow to
green), to near a thousand, some Milky Way visibility, to dark sky
(black). Based on DMSP nadir data. (Cinzano P., Falchi F., Elvidge
C.D., Baugh K.)
Slide 4
Highways agency Highways Agency. Responsible for major roads
and Motor Ways. HA has long since adopted Full Cut-off lighting on
all new Motor Ways, Also found now on new roundabouts in open
areas. NATA environmental impact appraisal. New Approach To
Appraisal - a high priority for the effect of the environmental
impact of lamps when choosing them. Is it working ? Rural
roundabout at Beckington, Somerset, on the A36 between Bath &
Warminster. before then re-lit with HCO lights (John Ball)
Slide 5
ILE Zones light levels Luminaires and installation
information
Slide 6
UK parliament S&T ctte and Gov initiatives A discussion in
the House of Lords was held in mid June. The Government is working
on the issue at the speed of light (!) ODPM to produce an annex to
PPS23, obliging councils to control external lighting through
planning requirements. Re. PPS23, Discussions are being held at the
Office of the Deputy Minister between stakeholders and Government
departments. Inc. ILE, RAS, and CfDS. DEFRA intention to make
lighting intrusion a statutory nuisance. 2003 The Science and
Technology Committee inquiry into light pollution and astronomy. A
lot of CFDS input written and aural evidence. Many recommendations,
Central recommendation.. That there should be legislation against
stray lighting. On 2004 Feb 12th There was a Parliamentary debate
on the report and its findings, at Westminster Hall.
Slide 7
Measuring rural skyglow Photometry of skyglow :- 1, Some
luminance profiles from rural locations. C J Baddiley Images by
James Weightman, Mike Tabb and Bob Mizon
Slide 8
Summary of finding dispelling myths Sky-glow in rural areas,
under atmospheric conditions where stars might be visible.
Dispelling assumptions and myths. Sky glow is due to light sent
directly upwards. No, it is not. It is also due to reflected light
straight up into the sky. No, it is not. In order to control it we
need to cut-out all directly upward light. No, we do not. When we
see skyglow on the horizon from a town, it is from the sky just
above the town. No, it is not. The reflected light is mostly from
road surfaces. No, it is not. It doesn't matter what sort of
luminaire is used, scattering in the atmosphere guarantees it ends
up as sky glow. Not true. Switching to white light will reduce sky
glow because such luminaries can be run at scotopically matched
lower intensity levels. Not necessarily. Shallow bowl lights
luminaires cause less sky glow than fuller cut-off types, because
less of them are needed per given road length. No, not
convincingly.
Slide 9
Elevated view of LA Los Angeles in 1988 (IDA). Individual light
sources dominate this scene, and the illumination of the sky behind
the viewer
Slide 10
Elevated view of Belfast Belfast form an elevated location
(Peter Paice).
Slide 11
Worcester (12 Km away) with its skyglow, the M5 motorway across
the Severn valley looking East, south of Worcester, from the
Malvern Hills. (Chris Baddiley) What you see is direct light from
many luminaires, right to the far side of Worcester. That is what
is illuminating the sky and clouds behind the viewer in the same
sight line in rural Herefordshire. All this is wasted light from
just above the horizontal. Elevated view of Worcester
Slide 12
Direct and reflected rays diagram Skyglow is caused by the
downward scattering of upward light by air molecules and also
aerosols, mostly water droplets and dust. The longer the path
length through the lowest part of the atmosphere, the more the
scattering. Light that goes straight up is mostly reflected, and
has shorter paths through the lower scattering layers. The low
angle light is mostly directly radiated, and it is this that causes
most of the sky glow well away from the source. Reflected Radiated.
Air molecules Aerosols
Slide 13
Visibility limit, star light and skyglow tables A table of
stellar magnitude, number of stars per square degree that are
visible to those limits and the total number of visible stars sky
and total illuminance. Compared with sky glow figures in the lower
table. Birmingham sky is about magnitude 17 per square arc second,
which is magnitude -1 per square degree and for the whole sky is 57
millilux on the ground. Darkest Holland is magnitude 20 per square
arc second and that is 3.6 millilux. Sky glow is still exceeding
the total starlight. In Birmingham it exceeds it by factor of
20.
Slide 14
Visibility limit map for Cotswolds Dark sky areas of the
Cotswolds (P. Cinzano - Dipartimento di Astronomia Padova, Italy),
Philips Maps publication for CfDS. Commercial publication, 2004
September
Slide 15
Illuminated cloud base Cotswolds 2003/8/20 at location SO967102
looking south (main glow Swindon 30+ Km SSE); Mars visible left.
Sagittarius right. Illumination of clouds from underneath Canon D60
digital SLR + 15mm f/2.8 lens. ISO 800 15 secs. (James
Weightman)
Slide 16
Skyglow in the Cotswolds Skyglow in Cotswolds, location
SO967102. Western quadrant, composite transformed to equal area
projection, CCD image images (James Weightman) Milky Way, Scutum,
Sagittarius etc taken last night 2003/8/2 at SO967102 near
Cirencester, Glos; Unguided Olympus C5050Z Even in the countryside,
there is no escape ! Note the gradation from the horizon upwards,
due to the concentration of scattering aerosols at lower altitudes.
The skyglow from very distant sources is still bight.
Slide 17
Analysis picture Skyglow in the Cotswolds CCD composite of 20
x15 second exposures. Cotswold Hills, 6 miles south of Cheltenham.
It can be seen, perhaps aided by the rising early morning mist,
that a glow can be seen all around the horizon, particularly at 12
o' clock. Location SO967102 (Cheltenham), 7 o'clock (Cirencester).
By James Weightman, BAA Made from 12 images covering the whole sky
taken with wide angle zoom 7 mm fl lens, setting of Casio QV3500
digital camera over a period of approx 15 minutes.
Slide 18
Cotswolds Weightman image, photometry Intensity profiles of
horizon to zenith lines as shown. The towns are from the top 12
o'clock Cheltenham, 7 o'clock Cirencester.
Slide 19
Cotswolds Weightman image, analysis The apparent elevations of
identified stars is compared with true elevations and corrected Sky
brightness Mag 18.5 /sq arcsec at Polaris.
Slide 20
Cotswolds, Mike Tabb image Sky glow in the countryside, from
distant towns from the darkest Cotswolds. The lens compresses
objects to the horizon (see the tree), so the dark hole overhead
appears actually smaller than shown. Location ST829 743 (Mike
Tabb). The towns, are clockwise from the top, Leigh Delamere,
Bristol, Bath, Trowbridge, Melksham, Chippenham, Swindon
Slide 21
Cotswolds, photometry Mike Tabb image Intensity profiles of
horizon to zenith lines as shown. The towns, are clockwise from the
top, Leigh Delamere, Bristol, Bath, Trowbridge, Melksham,
Chippenham, Swindon
Slide 22
Visibility limit map for Dorset Skyglow maps of the areas of
the Darkest Hampshire and Dorset, The New Forest (National Park)
(P. Cinzano - Dipartimento di Astronomia Padova, Italy), Philips
Maps publication for CfDS. Commercial publication, 2004
September
Slide 23
Poole, and ferry terminal Bob Mizon image Sky glow from
Poole
Slide 24
Poole photometry Intensity profiles of horizon to zenith lines
as shown. The curves fit well, despite this being a limited field
of view in which has a (Cos angle from the centre )^3 sensitivity
law, and the gamma of the film is unknown.
Slide 25
Rural skyglow estimation summary Sky brightness lower limit
estimates Cotswolds Weightman data Mag 18.6 /sq arcsec at 52 deg
elevation. Cotswolds Tabb data Mag 18.2 /sq arcsec at 52 deg
elevation. Poole Mizon data Mag 18.2 /sq arcsec at 30 deg
elevation.
Slide 26
Modelling luminaires and skyglow Photometry of skyglow :- 2,
Modelling luminaires, scatter, and skyglow C J Baddiley
Slide 27
Luminaire distributions Luminaire polar distributions and
ground reflections
Slide 28
Luminaires polar plot gamma for c=90/180 Luminaire light
distribution profile for a SOX luminaire (deep orange), shallow
bowl (light orange) and a full horizontal cutoff light (pink) of
the same total luminosity
Slide 29
Luminaires polar plot gamma and C Luminaire light distribution
profile for a SOX, (deep orange), shallow bowl (light orange) and a
full horizontal cutoff light (pink) of the same total luminosity
Note the radiance at horizontal in azimuth of the LPS SOX luminaire
shows its self- obscuration. 27% upward light ratio. Skyglow
modelling
Slide 30
Direct and surface reflected rays diagram At shallow angles
there is a reflected component that is enhanced by the increased
reflectivity of with incidence angle. Surfaces near grazing
incidence are blocked by hedges, buildings terrain etc.There is
also the direct upward component. Skyglow modelling Reflectivities:
at 589 nm wavelength Soil 0.1 Grass 0.08 Foliage 0.06 Asphalt 0.04
to 0.08 (dirty) Concrete 0.25 All direct light above horizontal not
blocked. Direct view radiated. Same view angle reflected Shallow
angle reflected light blocked. Reflected
Slide 31
Surface reflectivity vs angle Reflectivity as a function of
angle of incidence to normal. Reflectivites of surfaces increase
towards grazing incidence. Smooth surfaces go to unity. The
Brewster angle is before this which blocks the horizontally
polarised components. Most surfaces, even roughness are very
reflective beyond 70 degrees, i.e. below 20 degrees to the
horizontal. Low angel light is reflected, smooth ones become a
mirror. Grass reflectivity 0.1 Rises to 0.2 at 80 degrees, asphalt
goes from 0.04 to 1 at grazing angle, as does water
Slide 32
Surface reflectivity spectrum Reflectivities vary with
wavelength. Grass is less reflective in yellow. Switching to white
light increases its value. The minimum reflectivity is at about 670
nm where light is absorbed by photosynthesis, in common with all
vegetation. Reflectivities rise rapidly in the near infrared for
thermal rejection. Reflectivities: at 589 nm wavelength Soil 0.1
Grass 0.08 Foliage 0.06 Asphalt 0.04 to 0.08 (dirty) Concrete
0.25
Slide 33
Luminaires reflection and upper radiance polar plot gamma for
c=90/180 Luminaire light distribution profile showing downward and
sideways direct component and reflected components profile for a
LPS SOX (deep orange), shallow bowl HPS SON (light orange) and a
HPS SON full horizontal cutoff light (pink) of the same total
luminosity Elevation at azimuth 0/180,
Slide 34
Luminaires reflection and upper radiance polar plot gamma for c
Luminaire light distribution profile showing downward and sideways
direct component and reflected component, lumaires as before. Top
line elevation view for orthogonal azimuths, bottom line horizontal
azimuthal plot left and same but at 110 nadir, (20 degs above
horizontal) right. Skyglow modelling Azimuth plot at horizontal
Azimuth plot 5 deg above horiz. Azimuth plot 20 deg above horiz.
Elevation at azimuth 0/180, Elevation at azimuth 90/270,
Slide 35
SOX reflection and upper radiance polar plot gamma for c This
frame shows the polar plot for the reflected and direct upward
radiation in the vertical plane along the road, for the three light
types previously described. The low pressure sodium SOX light
source has a dominant direct radiated component which exceeds the
reflective component at low angles to the horizontal. Reflected
components have been blocked below 15 above horizontal as
previously described Skyglow modelling Radiated (orange), reflected
(green), total (red) SOX LPS Elevation at azimuth 0/180, Elevation
at azimuth 90/270, Azimuth plot 5 deg above horiz. Azimuth plot 20
deg above horiz.
Slide 36
Shallow bowl reflection and upper radiance polar plot gamma and
C The SON cases above the horizontal are all reflective. The
reflection pattern is nearly a mirror image of the ground luminance
distribution, convolved with the scatter distribution on the ground
surface. The asymmetry in the across road reflection is due to the
rd and verge boundary. Skyglow modelling Radiated (orange),
reflected (green), total (red) SOX LPS Elevation at azimuth 0/180,
Elevation at azimuth 90/270, Azimuth plot 5 deg above horiz.
Azimuth plot 20 deg above horiz. Shallow bowl SON
Slide 37
HCO reflection and upper radiance polar plot gamma and C The
asymmetry in the across road reflection is due to the rd and verge
boundary. Skyglow modelling Radiated (orange), reflected (green),
total (red) Elevation at azimuth 0/180, Elevation at azimuth
90/270, Azimuth plot 5 deg above horiz. Azimuth plot 20 deg above
horiz. HCO SON
Slide 38
Integrated luminance tables Luminance integrated over a sphere,
and upper hemisphere, direct, reflected and both, without and with
obstacle blocking of reflected rays below 15 degree elevation. Note
both the direct upward figures are high for the SOX luminaire. The
SOX reflection value is most reduced by the 15 degree elevation
obstacle blocking due to its wider spread on the ground compared
with the others.
Slide 39
Atmospheric scattering
Slide 40
Atmospheric scattering pictures Blue haze Rayleigh scattering
by particles smaller then the wavelength of light Daylight Rayleigh
scattering by air molecules, smaller than the wavelength of light.
Equal forward and backward scatter, also sideways, Varies as 1 /
wavelength 4 Mie scattering by aerosols.. water droplets and dust,
similar or larger than the wavelength of light. No wavelength
dependence and very directional.
Slide 41
Sunset scatterring simulation This is a sequence of a simulated
sunset. The Sun has been removed from this picture, just showing
the light scatter. Sky scatter from Sun (sun omitted) with
elevation Rayleigh scatter air molecules Mie scatter from aerosols
Total Scatter Sun Elev. 5 o 0 o -2.5 o -5 o -10 o
Slide 42
Scatter density with altitude The next plot shows the variation
of density of air molecules and aerosols, as a function of altitude
in the atmosphere. At 10 km altitude the density off the air has
reduced to 2/3 of its ground value. The equivalent height of the
total atmosphere brought to constant density is only a few Km.
Slide 43
Molecular scatter probability scatter probability for scatter
angle (phase function). Rayleigh scattering. Light is coming in
from below and being scattered in the direction of the grid angles.
The curve gives the probability of scatter in that direction. Equal
probability forwards and backwards, 50% of that sideways. The
probability over all angles =1 It varies in intensity as wavelength
^4 (blue biased). It is why the sky is blue by day
Slide 44
Aerosol scatter probability for scatter angle (phase) functions
(Mie scattering) (Heye-Greenstein function with added back
scatter). The forward scatter is very peaked, increasing with
particle size from 1nm to 10 microns The lower scatter probability
profile is the one used. There is practically no sideways scatter
and back scatter is tiny. No wavelength dependence, it is why
clouds are white Aerosol Mie scatter probability Dependence on
particle size
Slide 45
Incremental and cumulative scatter What is scattered out of the
beam is replaced by what is scattered into the beam. They have to
be the same over the path length. So 1 - the negative exponential
is the scattering into path. The proportion of light scattered out
of the beam is proportional to the length of the increment.
(proportional constant k) The input of the next increment is the
output of the previous one. This is the starting differential
equation that has the solution of an exponential accumulated
scatter with distance.
Slide 46
Path geometry Geometry
Slide 47
Path geometry The path distance x is replaced with a function
of elevation. The hypotenuse of the triangle shown. Maximum path
length are at the lowest elevation. z h = elevation R e = Earth
radius h = height of point z = total slant path k = scattering
coefficient Km -1 The negative exponential of (k x path length) is
then taken, but the path density decreases with height
Slide 48
Curved Earth geometry r h q d s ReRe ReRe ReRe t g r g d s
Slide 49
Results Photometry of skyglow Result plots Incremental vs.
distance along a given elevation path Total for vs. elevation at a
given distance Total for a given elevation vs. distance
Slide 50
Skyglow at high elevations. As all scatter is at large angles
it is mostly by air molecules, maximally in the blue. Little is
from the upper parts of the path, as there the scattering is near
orthogonal and the aerosol density is much lower. Air molecules
scattering at these large angles View elevation source angle All
large scatter angles All large scatter angles, very few molecules
up here Aerosols here but dont scatter at much at these high
angles, only direct radiation Ground reflection Direct radiance
(SOX)
Slide 51
Skyglow at low elevations. Much of the path has small scatter
angles, so is predominantly aerosol single Mie scattering, for
particles >50 microns in diameter. The scatter is strongly in
the forward direction. The peak contribution is forwards of the
source and is from aerosols. Little is from the upper parts of the
path, as there the scattering is near orthogonal and the aerosol
density is much lower. View elevation Small scatter angles Aerosols
dominating at low angles, forward scattering of direct radiance Air
molecules dominate scatter at these high angles, but only at a low
level. source angle Large scatter angles Peak of scatter is here,
aerosols dominating Ground reflection Direct radiance (SOX)
Slide 52
Incremental scatter plot for 45 deg elvn path The brightness
contribution to a 30 deg elevation view path, scatter at each point
along the inclined path in the direction of a source (15Km horiz.,
17 Km inclined path). Reflection for grass normal incidence
reflectivity 0.1. Obstruction of reflected rays up to 15 degrees.
Luminaires types SOX LPS (orange) and horizontal cutoff SON (pink).
Scatter just from aerosols (dots) and molecules (lower thin curves)
and combined (thick lines). Aerosols dominate at low
elevations.Molecules take over just above the source. Over source
(15Km horiz, 17Km at 30 degree elevation view path) To viewer
Aerosol scatter peak contribution
Slide 53
Scatter into line of sight for all elevations Skyglow at all
elevations, the sum of all the scattering along the path. Scatter
at low angles is from aerosols. Scatter at large angles it is
mostly by air molecules, maximally in the blue. Little is from the
upper parts of the path, as there the scattering is near orthogonal
and the aerosol density is much lower. All large scatter angles,
scatter from molecules only View elevation Forward scatter from
aerosols Scatter peak from aerosols Direct radiance (SOX) Ground
reflection All large scatter angles, scatter from molecules only
but at low level
Slide 54
Scatter components into line of sight for all elevations Total
line of sight scatter vs elevation view. Thin lines represent the
scatter due to air molecules, while the dots are those from
aerosols. The broad lines are the combination. The case of the low
pressure sodium and the horizontal cutoff lights are shown,
together was a reference curve fit to one of the measured data sets
discussed earlier. For the purpose of this calculation sixteen
light sources were evenly distributed about the horizon
representing the contribution from a number of towns, here also to
15 km distance. A crude correlation function was also applied to
cover the effect of multiple scattering. Aerosols (dots) dominate
at all but high elevations. The reduction in skygkkow from well
directed SON is a factor of up to 10. The relative brightness from
integrating along the full slant path from 16 ground sources equi-
spaced about the horizon, 15 km away, for elevations from
horizontal to the zenith. Luminaires types SOX LPS (orange) and
horizontal cutoff SON (pink). (obstruction of reflected rays up to
15 degrees, normal incidence reflectivity 0.1). Scatter just from
aerosols (dots) and molecules (lower thin curves) respectively.
Aerosols dominate at low elevations. Red thin curve is a
measurement.
Slide 55
Scatter for alll luminaires into line of sight for all
elevations The relative brightness from integrating along the full
slant path from 16 ground sources equi- spaced about the horizon,
15 km away, for elevations from horizontal to the zenith.
Luminaires types SOX LPS (deep orange), shallow bowls SON (light
orange), horizontal cutoff SON (pink), horizontal cutoff white
(grey) and shallow bowls white (pale blue). The relative brightness
from integrating along the full slant path from 16 ground sources
equi- spaced about the horizon, 15 km away, for elevations from
horizontal to the zenith. Luminaires types SOX LPS (deep orange),
shallow bowls SON (light orange), horizontal cutoff SON (pink),
horizontal cutoff white (grey) and shallow bowls white (pale
blue).
Slide 56
Scatter for grass and snow comparison Reflection off grass as
before, and reflection off snow, increases the brightness from the
HCOs and well directed types, as it is all from ground
reflections
Slide 57
Diagram of scatter into line of sight, at 45 degs elevation, as
function of distance from the source. 45 deg. View elevation
Scatter from Aerosols dominate Air molecules scatter but there are
few of them Skyglow at 45 deg. elevation, as a function of distance
form the source. Ground reflection Direct radiance (SOX)
Slide 58
Scatter into line of sight, at 45 degs elevation, as function
of distance from the source. The relative brightness contribution
of scatter at each point along a 45 degree elevation path in the
direction of a source as a function of source distance. Reflection
for grass. Luminaires types SOX LPS (orange) and horizontal cutoff
SON (pink). (obstruction of reflected rays up to 15 degrees).
Scatter just from aerosols (dots) and molecules (lower thin curves)
respectively. Walkers law has the brightness fall as 1/distance^2.5
(a constant slope on this plot), but here the slope increases with
distance.
Slide 59
Table of skyglow cause and effect Table of dominant and
secondary scattering for high and low elevations
Slide 60
Simulation and Summary
Slide 61
Light Pollution from different luminare types simulation The
next frame follows the same simulation scheme as was the sunset
sequence. but here we are just looking at the effects of the
different types of light previously discussed. Again from left or
right we have Rayleigh molecular scattering, Mie aerosol
scattering, and the combination. From top to bottom we have
luminaire types low pressure sodium, shallow bowl, and full cut
off, then HCO white, and shallow bowl white. This is only
indicative Sky scatter from type of luminaires (light source
omitted), from horizon upwards. Rayleigh scatter air molecules Mie
scatter from aerosols Total Scatter NOT HCO LPS Shallow bowls HCO
HPS HCO white Shallow bowls white
Slide 62
Summary Skyglow in the countryside is dominated by stray light
from towns, even 30Km away. This is still mostly from road lights.
Beams from unshielded luminaires just above the horizontal travel
though long path lengths and it is this that is mostly responsible
for rural skyglow in rural areas. These low angle beams of light
that and are scattered by aerosols in the forwards direction within
a few degrees. They illuminate the clouds and cause sky glow at
great distances, even 30Km away. Air molecule scattering only
dominates at high elevations The reduction in skyglow from adopting
horizontal cutoff lighting in all areas outside of town centres can
be a factor of 10 at 15 Km. Shallow bowls cause more skyglow then
HCOs due to the larger ground area of illuminance at angles closer
to horizontal and this is reflected into the sky. They are visually
more obtrusive too. If white light is adopted rather than HPS, then
the skyglow increases slightly though Rayleigh scattering by the
air at high elevations. This reduces some of the advantage in
running them at lower intensity levels for acceptable visual
scotopic perception, but only slightly.
Slide 63
Concluding points Glare and skyglow can be reduced in the
countryside by adoption of well controlled shielded lighting. Big
benefits local to the lights from cutting out glare and controlling
light spillage. Especially from sports facilities and amenities.
The best way to reduce skyglow is the adoption of HCOs in
preference to other types, even if this means more per road length.
But all measures are needed, such as dimming, as is now being
tried, and switching off when not necessary. Government funds are
available for improved quality lighting. But there is more and more
lighting for new housing and amenities. using HCOs alone may not
reduce sky glow sufficiently, against this growing amount of
lighting in the UK. There is soon to be a Government requirement on
all Councils to have lighting control measures in their planning
requirements (ODPM PPS23). The sale of domestic high power
intensity insecurity lights may also be restricted or banned (DEFRA
consultation).
Slide 64
Comet Ikeya Zhang in skyglow.2002. (anon) Comet Ikeya Zhang and
tree from a dark site. 2002 (Chris Baddiley). Ikeya Zhang
Slide 65
Hale Bopp Two pictures under dark sky conditions, comet Hale
Bopp (50mm lens), and The Milky Way Cygnus region (35 mm lens),..
CJB
Slide 66
Milky Way from La Palma Milky Way Cygnus and North American
nebula from La Palma (Chris Baddiley).
Slide 67
Information Addresses :- The British Astronomical Association
Campaign for Dark Skies, Burlington House, Piccadilly, London, W1J
0DU. Tel +44 120 7734 4145 CfDS Website
www.dark-skies.orgwww.dark-skies.org or. The Coordinator, CfDS, Bob
Mizon, 38 The Vineries, Colehill, Wimborne, Dorset BH21 2PX Email:
For the CD ROM image library . of good and bad lighting and its
effect on the environment(roads / security/ amenity/ building
floodlighting / Towns and countryside skyglow, views for space,
information and resources. . compiled by Chris Baddiley, Email:
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