|
|
|
Pierre Brunet |
|
Association Nationale pour la Protection du Ciel
Nocturne |
|
www.astrosurf.com/anpcn |
|
01 60 82 75 55 |
|
|
|
|
|
|
Aims |
|
Means |
|
A typical result |
|
Sensibility to the location : correlation to the
Cinzano/Falchi/Elvidge/Baugh Atlas of the artificial night sky brightness |
|
Sensibility to the location : moving a few
kilometers away |
|
Sensibility to the night hour : 3 hours apart |
|
Sensibility to the time of the year |
|
Sensibility to the meteorological conditions |
|
Conclusion and perspectives |
|
|
|
|
|
To show how the light pollution intensity
compares to the stars light |
|
To show the extent of light pollution domes |
|
To show how light pollution domes compare
between themselves (cities vs cities) |
|
To show how light pollution compare between
regions |
|
To give quantitative values (Ü digital camera) (to
come) |
|
To give an evolution with time (to come) |
|
|
|
|
|
|
|
|
|
The need for a fast and simple procedure : |
|
shooting the whole celestial vault in a single
operation |
|
|
|
|
|
|
|
Then |
|
A Single Lens Reflex with a f/1.8-50mm lens, |
|
A stainless steel hemi-spherical bowl (»360° field of view), |
|
|
|
|
|
|
|
|
|
|
|
|
|
And now |
|
A digital camera (Nikon Coolpix 5400) with a
f/2.8-5.6mm fish-eye lens (Nikon FC-E9) (190° field of view). |
|
|
|
|
|
|
|
|
|
Digital camera (1): |
|
5 megapixels |
|
100 ASA |
|
f/2.8 |
|
3 minutes exposure |
|
Noise reduction (dark frame) |
|
Full resolution in TIF format » 15 Mo. |
|
White balance : daylight |
|
Adobe Photoshop Elements LE 2.0 processing : |
|
Rotating (2) : North to the top |
|
Croping (3) |
|
Filtering (4) : |
|
polar coordinates → |
|
cartesian coordinates |
|
Scaling to 95°´360° (5) |
|
|
|
|
September 25th, 2003, 01h26AM, 5 km
NW of Livernon on D2 : Figeac-Livernon airport. |
|
Height 300 m. |
|
Clear. |
|
Level 4 on Bortle scale. |
|
|
|
|
|
|
September 25th, 2003, 01h26AM, 5 km
NW of Livernon on D2 : Figeac-Livernon airport. |
|
Height 300 m. |
|
Clear. |
|
Level 4 on Bortle scale. |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Agreement between the Cinzano & al. night
sky brightness atlas and the field situation (height must be accounted for)
; fair homogeneity of the field situation within each proposed pollution
level (white, red,…,grey). |
|
In a given location, there is not much to expect
from the time of the year, and quite nothing from the hour in the night. |
|
Meteorological conditions are a key feature, but
sky transparency exhibit an asymptotic value according to the pollution
levels defined by Cinzano & al. |
|
Digital data may lead to quantitative values for
the night sky brightness (to come). |
|
Keeping a same data acquisition procedure give
access to the evolution with time of light pollution (to come). |
|
|
|
|
|
|
A small village brightly lit all through the
night… |
|
Poznámky