Author: rascvan

Correct Outdoor Lighting

Correct Outdoor Lighting

correct outdoor lighting
correct outdoor lighting

Kudos to the lighting designer for this building.

The lighting on the Davis County (Utah) Library is a model of correct outfoor lighting techniques. Nothing glares in your eyes, no light trespasses on to adjascent properites. It’s lit to appropriate levels. I tried to make sure that the image I saw on the camera LCD matched what I saw with my eyes. The only difference was that I could actually see the stars.

It’s not the number of photons, but where they are directed that makes effective lighting.

Source: http://www.flickr.com/photos/makelessnoise/306868193/

What Is Skyglow?

skyglow as seen from earth
skyglow as seen from earth

One important issue with observing artificial night lighting from space that needs to be addressed is a phenomenon known as skyglow. Even in its pristine state the night sky is not completely dark. Some light comes from the stars, some from sunlight scattered by space dust in the plane of the solar system, and some from atmospheric gases subject to radiation and particle fluxes mostly from the sun (Clark 2008). This is called natural skyglow. Light emitted from human settlements in the atmosphere is refracted or scattered by air and water molecules and suspended particles (atmospheric aerosol) caused by dust, pollen, salt from sea spray, and waste products from industry (House of Commons 2003). Artificially illuminating the sky over great distances this is called artificial skyglow. In particular in the field of astronomy skyglow obscuring the night sky is an issue of utmost importance with extensive scientific research being conducted in recent years. Baddiley’s guide ‘Towards Understanding Skyglow’ (2007a) lists different sources contributing to skyglow in urban and rural areas. Furthermore a mathematical model of skyglow is presented considering different skyglow mechanisms (i.e. directly radiated light above the horizontal; reflected light from the road, ground and other surfaces; light scattered by air molecules; light scattered by aerosols) and different types of luminaires. According to Clark (2008) the total artificial light flux emitted by a city tends to be proportional to the product of two quantities, (1) the
number of light sources and (2) their mean output of light. Related to a growing economy and urban population growth typically both of these quantities increase over time. Considering artificial skyglow entails that the DMSP satellite sensors record much larger areas than just the immediate location of the lighting sources. Using satellite observed nighttime lights for delineating urban areas (Small et al. 2005) and approximating impervious surfaces (Elvidge et al. 2007) requires eliminating skyglow from the data, i.e. by applying thresholds to the digital number values. When dealing with ecological issues skyglow is a significant factor of light pollution as already very low light intensities alter the natural environment. Following recent approaches of modeling ecological impact of artificial night lighting (Aubrecht et al. 2008a) for the present analysis skyglow is thus not modeled out but rather considered as important contribution.

Artificial night lighting – light pollution

Artificial night lighting – light pollution

artificial night lighting
artificial night lighting

The footprint of human occupation is uniquely visible from space in the form of artificial night lighting – ranging from the burning of the rainforest to massive offshore fisheries to the omnipresent lights of cities and
towns and related connecting road networks (Aubrecht et al. 2008b, Doll 2008). The National Oceanic and Atmospheric Administration, National Geophysical Data Center (NOAA-NGDC) processes and archives nighttime lights data acquired by the U.S. Air Force Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS) which was initially designed to monitor the global distribution of clouds using visible and thermal infrared spectral bands. The DMSP satellites are in a sun-synchronous, low altitude polar orbit. With 14 orbits collected per day and a 3,000 km swath width, each OLS is capable of collecting a
complete set of images of the earth every 24 hours. At night the visible band signal is intensified with a photomultiplier tube (PMT) to enable the detection of moonlit clouds. The boost in gain enables the unique
capability of observing lights present at the earth’s surface at night. Most of the lights are from human settlements (Elvidge et al. 1997) and ephemeral fires (Elvidge et al. 2001a). Furthermore gas flares and
offshore platforms as well as heavily lit fishing boats can be identified.
NOAA-NGDC archives the long-term DMSP data from 1992 to present. For this project individual orbits were processed with automatic algorithms (described in Elvidge et al. 1997, 2001b) identifying image features (such as lights and clouds) and quality of the nighttime data. A cloud-free composite of nighttime lights was produced for 2003 using data from DMSP satellite F-15 (see figure 2). To identify the best nighttime lights data for creating an annual composite we adhered to the following standards:
• Only the center half of the orbital swath was used (best geolocation and sharpest features)
• Sunlight and moonlight were not present
• No solar glare contamination was allowed
• Only cloud-free images were used (based on thermal detection of clouds)
Nighttime image data from individual orbits meeting these criteria are the basis for a global latitude-longitude grid with 30 arc second resolution cells. This grid cell size corresponds to approximately 1
kilometer at the equator. In order to estimate the frequency with which lighting was present the total number of coverages and number of cloud-free coverages are tallied. The nighttime lights product used in the
presented analysis is the average digital number in the visible band of cloud-free light detections multiplied by the percent frequency of light detection. The inclusion of the percent frequency of detection term
normalizes the resulting digital values for variations in the persistence of flaring. For instance the value for a gas flare only detected half the time is discounted by 50 %. Background noise and land based fires were
filtered out.

Introducing "What's Up?", a new prelude to our monthly meetings

Starting at 7pm , half an hour before each monthly meeting, “What’s Up?” features a brief presentation of things to see in the sky that month.  Usually the presenter will also speak a few words on a topic of interest to new astronomers, especially young ones.

Our first “What’s Up?” presentation will take place at 7pm on February 10, 2011.  The topic will be ““Where’s the centre of the universe? What’s it expanding into? And where is the limit of our vision into space?” RASC President and SFU Professor Howard Trottier will demonstrate a do-it-yourself expanding universe and take questions from the audience.  He’ll also tell you how to find the Orion nebula and the moons of Jupiter!

Whats Up? February2011-PDF

SUPERnova Episodes 1-6

Episode 1 – “Telescopes and Orion”

Episode 2 – “The Stars, Our Sun & Ursa Major”

Episode 3 – “Light Pollution, Messier Marathons & Böotes”

Episode 04 – “The Moon, Astronomy for Kids & Lyra”

Episode 05 – “Cosmology, Deep Sky Observing & Aquila”

Episode 06 – “Imaging & Cassiopeia”

President’s Message for January 2011

On behalf of the Council of the Vancouver Centre of the RASC, and as its new President, I would like to take this opportunity to welcome you to the exciting start of a New Year of activities that is sure to inform our membership, reach out to the public, and provide many opportunities to experience the cosmos! I would also like to look ahead to a new set of opportunities for us to collectively strengthen our Vancouver Centre (VC).

I first wish to extend my warmest personal appreciation and affection to our Immediate Past President, Ron Jerome. At our 2010 AGM, Ron was publicly recognized by council for “his kind stewardship, and sage advice in directing our centre over the last two years as president” (to quote from Secretary Alan Jones’ AGM report). His leadership has set the stage for many of the new initiatives that will be brought forward by council this year, in concert with you, our membership.

We start off the year with a truly exceptional “catch” for our public meeting on January 13, when (thanks to our resourceful Speakers Chair, Barry Shanko) we host Dr. John Mather of the Goddard Space Flight Centre, co-recipient of the 2006 Nobel Prize in physics! Dr. Mather is currently a principal investigator for the James Webb Space Telescope (set for launch by 2015). He will talk about his work from the early 1990’s that led to his Nobel Prize, and will look ahead to the potential for the discovery of alien life by the new space telescope! (Looking for a short backgrounder on Dr. Mather’s Nobel Prize work? I give my take below ;). Our speaker line-up for the rest of 2011 already includes a noted amateur telescope maker and astro-imager, and a science writer with an intriguing story to tell, long-forgotten until now, of one man’s (impossible) dream to build the world’s largest telescope, on Grouse Mountain!

Look forward as well to a wide range of community events and star parties! VC is partnering with several groups committed to astronomy outreach, to put on events throughout the year and across the Greater Vancouver area and beyond. These groups already include Metro-Vancouver Parks, Simon Fraser University, the International Lunar Observatory Association, the NRC/Herzberg Institute of Astrophysics, the Vancouver Telescope Centre, and of course the HR MacMillan Space Centre.

Council has also set an ambitious set of goals to strengthen VC in 2011. First among these is to increase the value of VC for our membership. In particular, in February we will change the format of our monthly public meetings at the Space Centre, to include a short new “What’s Up?” segment, geared especially to newer and/or less experienced members, including practical tips on observing the night sky, and accessible segments on new developments in cutting edge astronomy and space science. This content should also help to attract new members, and might even be entertaining for more seasoned members ;).

Of prime importance is to increase membership, especially young families and university-age students. To this end, council aims to increase the presence of VC on the web, which will also increase service to our existing membership. This includes a revamped and higher-profile web site, with content to attract the public and of interest to our members. And we aim to connect VC to the public, and our members to each other, through Facebook and Twitter, including real-time postings from our events, and messages on anything astronomical that happens to grab the interest of our members! We also aim to capitalize on VC involvement with the successful Simon Fraser University outreach program for young families (on this I’m wearing two hats: see below).

Council also aims to establish new ways to encourage our members to volunteer, and to better coordinate our public events; to build on the recent successes of our Light Pollution Abatement campaign; to increase our media exposure (see our web site for my appearance as the new President of VC on the GlobalBC morning news show in December!); to make improvements to our observatory in Maple Ridge (the Antony Overton Memorial Observatory), and encourage use of that facility by our members, as well as by invitation to local university students; and to improve our telescope loaner program for VC members.
This might also be a good time to answer the questions “Who the heck am I?”, and “How the heck did I get on Vancouver Centre council?”, for the many members who I have yet to meet ;). While my day job is as a Professor of Physics at Simon Fraser University, my nighttime identity has for sometime been best described as Obsessive Amateur Astro-Imager (more on that in a future NOVA article!). But over the past two years my obsession for astronomy has fused with my day job, with SFU hosting a program of public outreach that has welcomed over 2,500 grade-school age kids at daytime astronomy workshops on the Burnaby campus, along with hundreds of their teachers, parents, and guardians. SFU has also hosted some 2,000 members of the public at evening star parties and special “theme” events over the past two years. And here’s the rub: None of this would have been remotely possible without the extraordinary support provided by Vancouver Centre, in the form of the many dedicated RASCal volunteers who assist at SFU events, and financial support that has provided educational resources through SFU to kids, teachers, and schools. Joining Vancouver Centre council began as a way for me to return a small part of that support. But this has turned into a wonderful avenue for doing more of what I love: sharing experiences with fellow amateur astronomers, and reaching out to the public. As President, I hope to help realize the many exciting new initiatives of Vancouver Centre, with my number one personal goal being to recruit new members, especially young people, who represent the future of VC.

Here finally is the backgrounder I promised on the work that won Dr. Mather the Nobel Prize ;). In 2006 the Nobel committee recognized Dr. Mather and Dr. George Smoot “for their discovery of the blackbody form and anisotropy of the cosmic microwave background radiation.” Their work as principal investigators of the COBE satellite mission in the early 1990s dramatically established the presence of very small variations, or anisotropies, in the temperature of the cosmic microwave background (CMB) radiation, the leftover “heat” of the Big Bang. These variations trace the tiny contrasts that were present in the distribution of matter in the early universe, and which grew to become the large-scale structures (immense galaxy clusters and super-clusters) that we see in the universe today. The detection of the anisotropies in the CMB (which “had” to be there) had been a “holy grail” of astrophysics ever since the discovery of the CMB itself in 1964, by Arno Penzias and Robert Wilson, for which they received the 1974 Nobel Prize. More precise measurements of the anisotropies in the CMB, to more deeply probe the physics of the early universe, continue to be an extremely hot pursuit in space science. These include stunning measurements of the age and geometry of the universe obtained by the NASA WMAP satellite, launched in 2001, and with still more penetrating results expected to come from the Planck satellite mission of the European Space Agency, launched in 2009.
In closing, I look forward to getting to know many more of our members, and I hope to encourage you to come forward and volunteer for any one of our many activities and initiatives. Please contact me, or any other member of council. Our contact information can be found on the VC web site.

Here’s to clear skies and more time under the stars!

Howard Trottier
President, RASC-VC
Professor of Physics, SFU

Resources

[rascvan]
This page has links to astronomy-related websites.