introduction. definition of light pollution. consequences of light

Željko Andreić: Introduction to light pollution, P1 1

Introduction to Light Pollution

Lecture 1

prof. Željko Andreić

Faculty of Mining, Geology and Petroleum EngineeringUniversity of Zagreb

[email protected]

http://rgn.hr/~zandreic/


Contents

1. introduction2. course overview3. literature4. consequences of light pollution5. measuring light pollution


What is light pollution?

Light pollution is any artificial light that spills into the environment.


thrown away -impacts the environment

trown away -brightens the night sky

The origin of light pollution

usefulllight

thrown away -impacts the environ-ment


The course owerview

Weakly schedule: 2+1 hours

The lecture time is flexible and is divided between lectures, pratical work

and the field work.

Main goal: to understand the light pollution and to be able to discern

between good and bad lighting habits.

Acessories: notebook and pencil, calculator


Criterion for signature: participating in course activities.

Exam: written seminar paper, optional oral exam.

Students can accept the seminar note, or attend the oral exam (subject of

the approval by the teacher).

The course owerview 2


1. Introduction. Radiometry and photometry basics. Definition of the

light pollution. Light in the nature at day and at night.

2. Bad impact of light pollution on the enviroment and humans.

Measuring the light pollution. Modelling tje ligh tpollution: ab-initio

physical model, its advantages and disadvantages.

3. Walker's law. Statistical model based on the walker's law. Setting

up the model and interpreting the results.

4. Sources of artificial light. Basig characteristics of light sources.

"Good" and "bad" lighting fictures.



5. Types of ligh tpollution and recomendations for limiting it.

6. Croatian legislation and comments on EU legislation concerning

light pollution.

7. Practical work: Statistical model of light pollution (computer lecture

room), measuring the light pollution in the field.

8. Field trip arround the city, discussing good and bad lighting

examples found on the way.



Literature:

1. presentations, course synopsis and other materials are at the web

adress:

http://rgn.hr/~zandreic/studenti/lp/lp_index.html

2. K. Narisada nad D. Screuder, Light pollution handbook, Springer 2004

3. B. Mizon, Light pollution, Springer 2002

4. Self-study manual on optical radiation measurements, NBS/NIST

5. scientific articles and other publications on LP



Consequences of light pollution

Light pollution degrades night landscapes. It increases the brigtness of the night sky and gives it unnatural yellow tint. It also changes night ecosystems.

UNESCO list of word heritage can also contain unique landscapes. Overlighting at night drastically degrades estetics of such night scenes.


Pravo na prirodno noćno nebo se smatra temeljnim ljudskim pravom

http://whc.unesco.org/en/astronomy/:

The sky, our common and universal

heritage, forms an integral part of the total

environment that is perceived by

mankind. Including the interpretation of

the sky as a theme in World Heritage is a

logical step towards taking into

consideration the relationship between

mankind and its environment. This step is

necessary for the recognition and

safeguarding of cultural properties and of

cultural or natural landscapes that

transcribe the relationship between

mankind and the sky.


Seneca, then and now...

"Da se zvijezde, umjesto što sjaju uvijek nad našim glavama, mogu vidjeti samo s jedne točke zemaljske kugle, ljudi ne bi prestali u hrpama onamo putovati, da motre nebo i da se dive čudesima neba." Seneca, prije oko 2000 god.

This is a sad truth today: those who can afford it travel far, even to another continents, just to see the natural night sky. European amateur astronomers today travel to Marko, Namibia, or, to see the southern skies, to Chile and Australia.


The night sky with little light pollution


The night sky with moderate light pollution


The night sky with strong light pollution


There is no natural darkness in Croatia anymore....


10%

40%30%

20%

fireflies live only here!

How much energy do we waste?



Plants: light impacts photosynthesis, regulates blooming, growth and rest periods. Artificial light can drastically changethis natural rhytm.

Too short nights can reduce or totally stop blooming.


Insects:

- most insect species can see UV light.

Experiment of catching insects with light:

HP mercury bulb: 8 400 insectsfluorescent bulb: 2 800HP natrium bulb: 1 760



Insects are massive victims

of light pollution


Birds:

- desorientation.

- changes of migration patterns, ending the migration and staying over winter in a wrong place.

- blinding and death by colisions with buildings or light sources.

- all night activity (gulls).



Airport Toronto, in a single night....


Animals:

- LP impacts orijentation (from improving it to total yeopardy).

- Lp affects atraction/repulsion and changes mating habits and cycles.

- LP changes or blocs byological rhytms and causes complex long-term consequences.

- LP changes habitat quality.



Sea tutles and other night animals suffer...


Humans:

- LP changes diurnal rhytms (sleep, feed periods, awakness, perpetual exostion, etc.).

- LP impacts the melatonin cycles, esp. hits women.

- LP changes seasonal rhytms due to artificially long days in winter.

- children myopia due to sleeping in lighted rooms.

- and?



What about humans?

women insomnia,

children shortsightness,

and?


Satellite imaging (Cinzano at al.)Measuring light pollution - satellite images


Satellite imaging + modelling (Cinzano at al.)Measuring light pollution - model based on satellite data


Monitoring methods: Sky quality meterMeasuring light pollution - Sky Quality Meter (SQM)


Monitoring methods: Sky quality meter

Half-width angular sensitivity: 42o

sensitivity 90o from axis: 1% max.

Measuring light pollution - Sky Quality Meter (SQM)



Half-width angular sensitivity: 10o

sensitivity 20o from axis: 1% max.

Measuring light pollution - Sky Quality Meter L (SQM-L)


Monitoring methods: Sky quality meterMeasurements in different directions (with SQM-L)

Two wedges, with angles of 15o and 30o.



90o 75o 60o 45o

30o 15o

Measurements in different directions (with SQM-L)


Astronomical scale for measuring star brightness is logaritmic:

(m2 - m1)

m2-m1 = 2,5log(I1/I2) or I1/I2 = 2,512

Unit of brightness is called magnitude (mag, or m)

Standard: Star Vega is used as m = 0,00.

The brightness of the sky is measured in mag/arcsec2. This unit of measure represents the equivalent brightness of sky area of 1square arc second with no stars in it).

Conversion to linear units: brightness in cd/m2 = 1,08×105×10(-0,4×m)

The magnitude scale for night sky brightness


Monitoring methods: all-sky camerasMeasuring light pollution - all-sky photography


Monitoring methods: all-sky cameras 2

mirror + digital WA lens + 35 mm film

Measuring light pollution - all-sky photography


Results 3 - middle Istria

Kanfanar Savičenta

SQM: 20,8 21,0

Measuring light pollution - all-sky photography


Results 3 - middle Istria

Kanfanar Savičenta

SQM: 20,8 21,0

The report on light pollution measurements

The report contains:

- description of the site where measurements were taken- date and time of mesurements- description of meteorological and astronomical conditions atthat moment

- visual assesment of the night sky quality- results of the night sky brightness measurements- conclusions

- Names of persons that did the measurements or data reduction are quoted on the first page of the report, togetherwith a short summary of the most important facts about the site.


Site description

- a short description of the site and ways of reaching it.- geographic coordinates of the location (GPS, or taken from Google Earth)

- meteorological and astronomical conditions.- photos taken at day, horizon panorama, etc.


The site at day


Horizon panorama -

individual images


N E NS W

Horizon panorama - composite


Meteorological and astronomical conditions at the site

- A short description of meteorological conditions at the time ofmeasurements, like presence of clouds, temperature and humidity, assesment of atmospheric transparency and aerosols, etc.- presence/absence of the Moon and its phase (if present), sky conditions (clear, foggy, ciruss clouds, etc.)


Visual assesment of the sky quality

- the limiting magnitude.- sky quality according to the Bortle scale.- detailed description of the appearance of the night sky, depending on the observers experience. Unexperiencedobserver will not be able to do this assesment, in which case it is left out of the report.


The limiting magnitude

- is the brightness of the faintest star one can see near zenith.


SQM-L measurements

- details and short comments (if needed) are given.

a. sky brightness at zenith, often the only data nedded:

21,3522:40

21,4221:44

21,3621:29

21,4321:15

sky brightnessmag/arcsec2

local time

mean value: 21,39


b. detailed measurements - better assesment of light pollutionnear horizon. Measurements are taken in several directions,for each 15o in height.

18,8817,9315

20,1419,1030

20,4219,8245

20,5620,1560

20,5820,4175

20,46zenith

ENW Sheight\direction

SQM-L measurements


Graphical presentation:

zone borders at:

7,5o

22,5o

37,5o

52,5o

67,5o

82,5o

max. 29 measurements

N

S

W E


N

S

W E20,46

20,41

20,15

19,82

19,10

17,93

18,88

20,14

20,42

20,56

20,58

Graphical presentation:


All-sky

photography


N

S

EW

60o

30o

0o

All-sky

photography


20% izofote od svjetline u zenitu

N

S

E W

60o

30o

0o

All-sky photography - isophotes

isophote step 20% of

the brightness in the zenith

introduction. definition of light pollution. consequences of light

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