The Dark Side of the Sky: Seeing, Protecting & Recovering the Night Sky
Shane L. Larson Department of Physics Utah State University
Cache Valley Stargazers Logan, UT 12 October 2012
1 First things first...
2 First things first...
2 Storyline
Why we care about the dark
The problem
Why everyone should care
Effective lighting
3 Why we love the dark...
The Milky Way
4 Why we love the dark...
The stars
5 Why we love the dark...
Aurora Borealis
Pic on Oct 9, by Mark Waegner, from Benson
6 Why we love the dark...
The Veil Nebula
7 Why we love the dark... Comet C/2012 S1 (ISON)
Will pass within 1.6 million miles of the Sun (about 3 solar radii)
Will heat tremendously
Will pass close to Earth before Christmas 2013
Bright as full Moon!
“Once in a civilization’s lifetime event” GREAT COMET OF 1680
8 The Earth at Night
Seeing the night sky is often at odds with the “lights of progress” ––– our civilization is visible from space
9 The US at Night
Every point of light is a city...
10 The US at Night
...but the light extends far outside the cities!
11 The Western US at Night
In the west, we still have vast tracks of land that are dark night skies
Natural Bridges was the first in the nation to be designated “Dark Sky Parks”
12 Bortle Scale
13 14 SQM
We can accurately measure the night sky brightness with simple handheld devices
Logan (USU) = 18.90
Palomar = 21.24
Paradise = 21.05
15 Why is the sky lit up?
We don’t need tools any more fancy than our eyes to tell us the sky is lit up.
The real questions are:
WHY is the sky lit up?
What can we do about it?
LOGAN SKYGLOW FROM PARADISE
16 Ineffective Lighting
Ineffective lighting is robbing us of our night skies!
We need/want light on the ground, so light directed upwards is wasted!
GLARE
17 We don’t realize it!
18 So what?
So is this just a bunch of astronomers grousing about seeing the stars?
Why should I care?
The United States spends $1 billion/year on electricity for the light that goes to the sky.
In Cache Valley, that is about $350,000/year
19 So what?
Noctural Animals are being disrupted by light
Bird migratory patterns disrupted by illuminated cities
Frogs cease their mating songs under artificial lights
Baby sea turtles turn toward cities rather than the reflected light on the sea.
20 So what?
In humans, excessive exposure to light (at night) decreases melatonin
Increases in cancer risk
LIGHT TRESPASS
21 Glare & Shielding
We want light on the ground, where we are.
Glare is sideways and upward light that can be seen far away
22 Glare & Shielding
Effective fixtures improves lighting where we need it, and also:
reduces glare
reduces upward waste
reduces light pollution
23 Fixtures
Choosing good fixtures is the first step to improving lighting.
You can do this, as can cities!
24 Fixtures @ Home
In principle, bad fixtures cost the same amount as good fixtures.
Finding them is not always easy!
We “reduced glare” but still don’t have full cutoff fixtures. :-(
25 Last thoughts...
We have all kinds of reasons to want to protect the night sky
It is easy to adopt good practices with new lighting; it costs nothing, and saves on energy costs
It costs money to fix bad lighting, but in the end there are good benefits THANK YOU!
26 Links
International Dark Sky Association (IDA)
http://www.darksky.org
Dark Skies Awareness
http://www.darkskiesawareness.org
Globe at Night
http://www.globeatnight.org
Dark Sky Finder
http://www.jshine.net/astronomy/dark_sky/
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