DOCSLIB.ORG

Visual Estimations of Night Sky Brightness

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Visual Estimations of Night Sky Brightness Chadwick A. Moore Visual Estimations of Night Sky Brightness We can no longer avoid the issue of light pollution, because soon we will have nowhere left to go. The global problem of light pollution has never been so artfully expressed as in Woodruff T. Sullivan’s famous ‘Earth at Night’ satellite images.* Kosai and Isobe 1992 anagers of parks, preserves, refuges, and wilderness areas are becoming increasingly concerned over the loss in visibility of the night sky. Like the apocalyptic threat of Rachel Carson’s Silent Spring, those who cherish the night skies fear a night of no stars, with only the sallow glow of streetlights for inspira- Mtion. Encroaching city lights scatter light upward, bathing the otherwise dark sky and reducing the contrast to a point where stars are lost in urban glow. The effect of urban lighting, also known as light pollution, can reach surpris- ingly far. For example, from Death Valley National Park the lights of Las Ve- gas produce an obvious and obtrusive glow even though the city is 100 miles to the southeast. Los Angeles, 160 miles to the southwest, produces a dim but broad glow across the southern horizon (Moore and Duriscoe, in prep.). Astronomers at observatories contrast, and atmospheric extinction. were perhaps first to notice this However, less costly tools are avail- problem. As early as 1970, astrono- able to those interested in monitoring mers were scouring the USA for suit- their dark sky resource. The simplest able observing sites away from city and least costly monitoring methods lights; remaining opportunities were are visual estimations using the hu- few (Walker 1970; Garstang 1989). man eye. Today, astronomical observatories Under a pristine dark sky, per- employ multi-million-dollar equip- haps 14,000 stars in the celestial ment to measure sky brightness, sphere would be discretely visible _______________ * 46 The George Wright FORUM (Figure 1). Outdoor lighting tends to trast between the background and scatter light upward, brightening the fainter stars until they become invisi- background of space. This increase ble to the eye. Also lost with the stars in sky brightness reduces the con- are the diffuse objects in the sky— Volume 18 • Number 4 2001 47 nebulae, galaxies, comets, and the ever, what the eye lacks in precision, river of stars in our galaxy called the it makes up for in sensitivity and ease Milky Way. The visible loss of these of use. The scoptic (grayscale) vision faint and diffuse astronomical objects we use at night is surprisingly sensi- is what troubles amateur astronomers tive, able to detect as few as 200 so much. This group has been the photons per second falling on the most vocal in opposing light pollu- retina and transmitting a message to tion and promoting the conservation the brain (Russell 1917). The eye’s of dark night skies. rod cells are 1,000 times more sensi- Amateur astronomers and meteor tive than the color-detecting cone observers have made visual estima- cells (Carr et al. 1989b). Scoptic vi- tions of limiting magnitude for years. sion is most sensitive in the greens Limiting magnitude is a measure of and blues, and least sensitive to the the brightness of the faintest star one reds; thus the use of red-filtered can see. The astronomical magnitude flashlights to preserve night vision. scale increases with faintness. Mag- The star magnitudes used in this nitude zero represents bright stars method are measured in the “John- such as Vega, Antares, or Rigel, son V” spectrum, which closely while magnitude 7 stars would be matches the human eye’s scoptic vi- near the faint limit of most dark skies. sion, and are therefore an appropri- In exceptional cases, magnitude 8 ate analogue for brightness meas- stars have been observed with the urements. naked eye (Russell 1917; Bowen 1947). The number of visible stars, and the diversity of astronomical The visual estimation of limiting objects visible, decrease rapidly as magnitude is based on star counts of the limiting magnitude falls. It is not 25 established sample areas (similar uncommon for a remote area sur- to methods utilized by meteor ob- rounded by rapid urbanization to servers; Figure 2). Each area contains lose more than half the visible stars in a field of mapped stars with known a decade (Moore and Duriscoe, in brightness values. The observer prep.). scans the field using averted vision, The human eye is a somewhat trying to detect sequentially fainter imprecise instrument. Few people stars on the map. The faintest star have 20/20 vision without aid of observed becomes the sky’s limiting lenses, and the eye changes in light- magnitude (LM). By following the gathering capability and acuity with procedures for dark adaptation and age (Carr et al. 1989b). There is also counting, reasonable conformity can potential for bias in the eye’s central be attained between observers processing unit— the brain. How- (Blackwell 1946). 48 The George Wright FORUM Initially, this star count is con- fying some light sources while sup- ducted at the zenith (straight over- pressing others. The effect of local head). Counts can also be conducted weather upon sky brightness is an in quadrants of the sky, and at vari- interesting study in itself, but such ous angular altitudes above the hori- conditions should be avoided to zon. The process can take as little as produce a baseline inventory to track 30 minutes to arrive at a zenith LM long-term changes. number. Observers have used this methodology to produce brightness maps of different parts of the night sky, or to take single measurements Light scattered upward is not the on multiple nights to capture the only factor affecting an LM meas- range of variation associated with urement. Pollutants in the atmos- weather, seasonal changes, or atmos- phere can substantially increase the pheric scattering. Observations are extinction of light as it is transmitted conducted under cloudless, moon- through the atmosphere. Airborne less nights. Even distant clouds or particulates, in the absence of light ground fog skew the results, ampli- pollution, can substantially reduce Volume 18 • Number 4 2001 49 the faintest stars visible, even thought notice that the stars look sharpest the sky background may appear very and brightest in the late hours just dark (Garstang 1991). In this case, before dawn. This trend is mostly the visibility of stars and astronomi- due to atmospheric turbulence which cal objects are lost to light scattering settles and diminishes as the night and absorption, not due to decreased progresses and the land cools. This contrast. Air pollution compounds trend may also be the result of re- the scattering of light pollution, fur- duced light pollution as people turn thering the degradation of night sky off their porch lights, park their cars, visibility. Finally, both factors are and outdoor athletic events come to a affected by humidity in the atmos- close. phere (Carr et al. 1989b). The growth and size of aerosol particles in the atmosphere is related to As with many natural resource moisture. Therefore, higher humid- measurements, much of the chal- ities are expected to exacerbate both lenge can be separating the natural the scattering of existing light pollu- and human components. Natural sky tion as well as the absorption of star- brightness does exist; the human- light (Garstang 1991). Conditions of made component of sky brightness is greater scattering tend to brighten light pollution. Moonlight is the most nearby light sources while dimming obvious natural source, but can eas- far-off light sources (Carr et al. ily be avoided by sampling when the 1989b). The corollary to this phe- moon has set. Zodiacal light, the nomenon is that dry, high-altitude spike of illuminated dust particles dark-sky sites are more susceptible to circling the inner solar system, can far-off light sources. be a significant natural light source. The lower atmosphere is turbu- It is most obvious in spring and lent, producing the common effect of autumn, but will set a few hours after twinkling stars. Turbulence scatters sunset and rise a few hours before light and reduces the LM. Those dawn. Like the moon, zodiacal light precious few photons will be de- is easily avoided and simply results flected away from a single retinal cell, in a shorter observing window at and the eye will fail to detect a star, night (International Dark-Sky Asso- even though the night is dark and ciation 2000). pollution-free (Bortle 2001). There- Airglow is an important consid- fore, LM estimations will integrate a eration at dark-sky locations. This measure of atmospheric stability, results from the excitation of air when perhaps we are less interested molecules in the upper atmosphere in its effects than that of scattered that emit faint light. Airglow varies light or air pollution. Observers often with solar activity, and tends to be 50 The George Wright FORUM highest during the solar maximum class 1 skies are so rare now that few (which varies on an 11-year cycle; have ever seen them. the most recent was in 2001). Lastly, The Bortle scale definitions are galactic light and starlight can be a included and cross–referenced with significant enough light source that LMs (Figure 3). The Bortle scale is they can affect both the eye’s ability suitable for a wide range of condi- to see faint objects and the brightness tions, from the brightest urban areas of the sky itself. Star counts within (LM lower than 4) to the darkest the Milky Way are more difficult due sites (LM up to 8)—an advantage to the glowing background of the over the LM star count method.
Load more

Recommended publications
  • Lift Off to the International Space Station with Noggin!
    Lift Off to the International Space Station with Noggin! Activity Guide for Parents and Caregivers Developed in collaboration with NASA Learn About Earth Science Ask an Astronaut! Astronaut Shannon Children from across the country had a Walker unique opportunity to talk with astronauts aboard the International Space Station (ISS)! NASA (National Aeronautics and Space Administration) astronaut Shannon Astronaut Walker and JAXA (Japan Aerospace Soichi Noguchi Exploration Agency) astronaut Soichi Noguchi had all of the answers! View NASA/Noggin Downlink and then try some out-of-this- world activities with your child! Why is it important to learn about Space? ● Children are naturally curious about space and want to explore it! ● Space makes it easy and fun to learn STEM (Science, Technology, Engineering, and Math). ● Space inspires creativity, critical thinking and problem solving skills. Here is some helpful information to share with your child before you watch Ask an Astronaut! What is the International Space Station? The International Space Station (ISS) is a large spacecraft that orbits around Earth, approximately 250 miles up. Astronauts live and work there! The ISS brings together astronauts from different countries; they use it as a science lab to explore space. Learn Space Words! Astronauts Earth An astronaut is someone who is Earth is the only planet that people have trained to go into space and learn lived on. The Earth rotates - when it is day more about it. They have to wear here and our part of the Earth faces the special suits to help them breathe. Sun, it is night on the other side of the They get to space in a rocket.
    [Show full text]
  • Chapter 3: Familiarizing Yourself with the Night Sky
    Chapter 3: Familiarizing Yourself With the Night Sky Introduction People of ancient cultures viewed the sky as the inaccessible home of the gods. They observed the daily motion of the stars, and grouped them into patterns and images. They assigned stories to the stars, relating to themselves and their gods. They believed that human events and cycles were part of larger cosmic events and cycles. The night sky was part of the cycle. The steady progression of star patterns across the sky was related to the ebb and flow of the seasons, the cyclical migration of herds and hibernation of bears, the correct times to plant or harvest crops. Everywhere on Earth people watched and recorded this orderly and majestic celestial procession with writings and paintings, rock art, and rock and stone monuments or alignments. When the Great Pyramid in Egypt was constructed around 2650 BC, two shafts were built into it at an angle, running from the outside into the interior of the pyramid. The shafts coincide with the North-South passage of two stars important to the Egyptians: Thuban, the star closest to the North Pole at that time, and one of the stars of Orion’s belt. Orion was The Ishango Bone, thought to be a 20,000 year old associated with Osiris, one of the Egyptian gods of the lunar calendar underworld. The Bighorn Medicine Wheel in Wyoming, built by Plains Indians, consists of rocks in the shape of a large circle, with lines radiating from a central hub like the spokes of a bicycle wheel.
    [Show full text]
  • Introduction to Astronomy from Darkness to Blazing Glory
    Introduction to Astronomy From Darkness to Blazing Glory Published by JAS Educational Publications Copyright Pending 2010 JAS Educational Publications All rights reserved. Including the right of reproduction in whole or in part in any form. Second Edition Author: Jeffrey Wright Scott Photographs and Diagrams: Credit NASA, Jet Propulsion Laboratory, USGS, NOAA, Aames Research Center JAS Educational Publications 2601 Oakdale Road, H2 P.O. Box 197 Modesto California 95355 1-888-586-6252 Website: http://.Introastro.com Printing by Minuteman Press, Berkley, California ISBN 978-0-9827200-0-4 1 Introduction to Astronomy From Darkness to Blazing Glory The moon Titan is in the forefront with the moon Tethys behind it. These are two of many of Saturn’s moons Credit: Cassini Imaging Team, ISS, JPL, ESA, NASA 2 Introduction to Astronomy Contents in Brief Chapter 1: Astronomy Basics: Pages 1 – 6 Workbook Pages 1 - 2 Chapter 2: Time: Pages 7 - 10 Workbook Pages 3 - 4 Chapter 3: Solar System Overview: Pages 11 - 14 Workbook Pages 5 - 8 Chapter 4: Our Sun: Pages 15 - 20 Workbook Pages 9 - 16 Chapter 5: The Terrestrial Planets: Page 21 - 39 Workbook Pages 17 - 36 Mercury: Pages 22 - 23 Venus: Pages 24 - 25 Earth: Pages 25 - 34 Mars: Pages 34 - 39 Chapter 6: Outer, Dwarf and Exoplanets Pages: 41-54 Workbook Pages 37 - 48 Jupiter: Pages 41 - 42 Saturn: Pages 42 - 44 Uranus: Pages 44 - 45 Neptune: Pages 45 - 46 Dwarf Planets, Plutoids and Exoplanets: Pages 47 -54 3 Chapter 7: The Moons: Pages: 55 - 66 Workbook Pages 49 - 56 Chapter 8: Rocks and Ice:
    [Show full text]
  • TAKE-HOME EXP. # 1 Naked-Eye Observations of Stars and Planets
    TAKE-HOME EXP. # 1 Naked-Eye Observations of Stars and Planets Naked-eye observations of some of the brightest stars, constellations, and planets can help us locate our place in the universe. Such observations—plus our imaginations—allow us to actively participate in the movements of the universe. During the last few thousand years, what humans have said about the universe based on naked-eye observations of the night and day skies reveals the tentativeness of physical models based solely on sensory perception. Create, in your mind's eye, the fixed celestial sphere. See yourself standing on the Earth at Observer's the center of this sphere. As you make the zenith + star-pattern drawings of this experiment, your perception may argue that the entire sphere of fixed star patterns is moving around the Earth and you. To break that illusion, you probably have to consciously shift your frame of º reference—your mental viewpoint, in this 50 up from the horizon case— to a point far above the Earth. From South there you can watch the globe of Earth slowly Observer on local horizon plane rotate you , while the universe remains essentially stationary during your viewing It is you that turns slowly underneath a fixed and unchanging pattern of lights. Naked eye observations and imagination has led to constellation names like "Big Bear" or "Big Dipper". These names don't change anything physically —except, and very importantly, they aid humans' memory and use of star patterns. A. Overview This experiment involves going outside to a location where you can observe a simple pattern of stars, including at least 2, but preferably 3 or 4 stars.
    [Show full text]
  • GLOBE at Night: Using Sky Quality Meters to Measure Sky Brightness
    GLOBE at Night: using Sky Quality Meters to measure sky brightness This document includes: • How to observe with the SQM o The SQM, finding latitude and longitude, when to observe, taking and reporting measurements, what do the numbers mean, comparing results • Demonstrating light pollution o Background in light pollution and lighting, materials needed for the shielding demo, doing the shielding demo • Capstone activities (and resources) • Appendix: An excel file for multiple measurements CREDITS This document on citizen-scientists using Sky Quality Meters to monitor light pollution levels in their community was a collaborative effort between Connie Walker at the National Optical Astronomy Observatory, Chuck Bueter of nightwise.org, Anna Hurst of ASP’s Astronomy from the Ground Up program, Vivian White and Marni Berendsen of ASP’s Night Sky Network and Kim Patten of the International Dark-Sky Association. Observations using the Sky Quality Meter (SQM) The Sky Quality Meters (SQMs) add a new twist to the GLOBE at Night program. They expand the citizen science experience by making it more scientific and more precise. The SQMs allow citizen-scientists to map a city at different locations to identify dark sky oases and even measure changes over time beyond the GLOBE at Night campaign. This document outlines how to make and report SQM observations. Important parts of the SQM ! Push start button here. ! Light enters here. ! Read out numbers here. The SQM Model The SQM-L Model Using the SQM There are two models of Sky Quality Meters. Information on the newer model, the SQM- L, can be found along with the instruction sheet at http://unihedron.com/projects/sqm-l/.
    [Show full text]
  • The Midnight Sky: Familiar Notes on the Stars and Planets, Edward Durkin, July 15, 1869 a Good Way to Start – Find North
    The expression "dog days" refers to the period from July 3 through Aug. 11 when our brightest night star, SIRIUS (aka the dog star), rises in conjunction* with the sun. Conjunction, in astronomy, is defined as the apparent meeting or passing of two celestial bodies. TAAS Fabulous Fifty A program for those new to astronomy Friday Evening, July 20, 2018, 8:00 pm All TAAS and other new and not so new astronomers are welcome. What is the TAAS Fabulous 50 Program? It is a set of 4 meetings spread across a calendar year in which a beginner to astronomy learns to locate 50 of the most prominent night sky objects visible to the naked eye. These include stars, constellations, asterisms, and Messier objects. Methodology 1. Meeting dates for each season in year 2018 Winter Jan 19 Spring Apr 20 Summer Jul 20 Fall Oct 19 2. Locate the brightest and easiest to observe stars and associated constellations 3. Add new prominent constellations for each season Tonight’s Schedule 8:00 pm – We meet inside for a slide presentation overview of the Summer sky. 8:40 pm – View night sky outside The Midnight Sky: Familiar Notes on the Stars and Planets, Edward Durkin, July 15, 1869 A Good Way to Start – Find North Polaris North Star Polaris is about the 50th brightest star. It appears isolated making it easy to identify. Circumpolar Stars Polaris Horizon Line Albuquerque -- 35° N Circumpolar Stars Capella the Goat Star AS THE WORLD TURNS The Circle of Perpetual Apparition for Albuquerque Deneb 1 URSA MINOR 2 3 2 URSA MAJOR & Vega BIG DIPPER 1 3 Draco 4 Camelopardalis 6 4 Deneb 5 CASSIOPEIA 5 6 Cepheus Capella the Goat Star 2 3 1 Draco Ursa Minor Ursa Major 6 Camelopardalis 4 Cassiopeia 5 Cepheus Clock and Calendar A single map of the stars can show the places of the stars at different hours and months of the year in consequence of the earth’s two primary movements: Daily Clock The rotation of the earth on it's own axis amounts to 360 degrees in 24 hours, or 15 degrees per hour (360/24).
    [Show full text]
  • Night Sky Monitoring Program for the Southeast Utah Group, 2003
    NIGHT SKY United States Department of MONITORING Interior National Park Service PROGRAM Southeast Utah Group SOUTHEAST UTAH GROUP Resource Management Division Arches National Park Canyonlands National Park Moab Hovenweep National Monument Utah 84532 Natural Bridges National Monument General Technical Report SEUG-001-2003 2003 January 2004 Charles Schelz / SEUG Biologist Angie Richman / SEUG Physical Science Technician EXECUTIVE SUMMARY NIGHT SKY MONITORING PROGRAM Southeast Utah Group Arches and Canyonlands National Parks Hovenweep and Natural Bridges National Monuments Project Funded by the National Park Service and Canyonlands Natural History Association This report lays the foundation for a Night Sky Monitoring Program in all the park units of the Southeast Utah Group (SEUG). Long-term monitoring of night sky light levels at the units of the SEUG of the National Park Service (NPS) was initiated in 2001 and has evolved steadily through 2003. The Resource Management Division of the Southeast Utah Group (SEUG) performs all night sky monitoring and is based at NPS headquarters in Moab, Utah. All protocols are established in conjunction with the NPS National Night Sky Monitoring Team. This SEUG Night Sky Monitoring Program report contains a detailed description of the methodology and results of night sky monitoring at the four park units of the SEUG. This report also proposes a three pronged resource protection approach to night sky light pollution issues in the SEUG and the surrounding region. Phase 1 is the establishment of methodologies and permanent night sky monitoring locations in each unit of the SEUG. Phase 2 will be a Light Pollution Management Plan for the park units of the SEUG.
    [Show full text]
  • The Dawn Sky Brightness Observations in the Preliminary Shubuh Prayer Time Determination
    QIJIS: Qudus International Journal of Islamic Studies Volume 6, Issue 1, February 2018 THE DAWN SKY BRIGHTNESS OBSERVATIONS IN THE PRELIMINARY SHUBUH PRAYER TIME DETERMINATION Laksmiyanti Annake Harijadi Noor Bandung Institute of Technology (ITB) Bandung, West Java [email protected] Fahmi Fatwa Rosyadi Satria Hamdani Bandung Islamic University (UNISBA) Bandung, West Java [email protected] Abstract The indication of began to enter the shubuh prayer time is when emerge the morning dawn and lasted until the sun rises. The sun position when emerge the morning dawn is below the intrinsic horizon marked with a minus sign (-) with the value of a certain height. The Ministry of Religious Affairs has set the sun altitudes of dawn in the shubuh prayer time with minus (-) 19° + sunrise/sunset altitudes as standard is the reference time of dawn prayers in Indonesia. However, this provision in fact reap discourse in some quarters because it is not in accordance with the phenomenon of morning dawn emergence at the beginning of the shubuh prayer time empirically. This study aims to decide the morning dawn, as the beginning of dawn determinant. The tool used in this study is the Sky Quality Meter (SQM), to detecting the morning dawn emergence as a sign of the beginning of the shubuh prayer time. The results of this study found that the brightness of the sky throughout Fahmi Fatwa Rosyadi Satria Hamdani the night or the morning dawn in Tayu Beach, Pati, Central Java, in the span of four days of observation that is at 04.31 A.M. with an average altitude of the sun is -17°(17° below the horizon).
    [Show full text]
  • Daytime Sky Brightness Characterization for Persistent GEO SSA
    Daytime sky brightness characterization for persistent GEO SSA Grant M. Thomas Air Force Institute of Technology, Wright-Patterson AFB, Ohio Richard G. Cobb Air Force Institute of Technology, Wright-Patterson AFB, Ohio ABSTRACT Space Situational Awareness (SSA) is fundamental to operating in space. SSA for collision avoidance ensures safety of flight for both government and commercial spacecraft through persistent monitoring. A worldwide network of optical and radar sensors gather satellite ephemeris data from the nighttime sky. Current practice for daytime satellite tracking is limited exclusively to radar as the brightening daytime sky prevents the use of visible-band optical sensors. Radar coverage is not pervasive and results in significant daytime coverage gaps in SSA. To mitigate these gaps, optical telescopes equipped with sensors in the near-infrared band (0.75-0.9µm) may be used. The diminished intensity of the background sky radiance in the near-infrared band may allow for daylight tracking further into the twilight hours. To determine the performance of a near-infrared sensor for daylight custody, the sky background radiance must first be characterized spectrally as a function of wavelength. Using a physics-based atmospheric model with access to near-real time weather, we developed a generalized model for the apparent sky brightness of the Geostationary satellite belt. The model results are then compared to measured data collected from Dayton, OH through various look and Sun angles for model validation and spectral sky radiance quantification in the visible and near-infrared bands. 1 INTRODUCTION Spectral sky radiance or spectral sky brightness is a measure of the radiant intensity at each wavelength of the atmosphere.
    [Show full text]
  • NATURE [Nov. 22, R877 Addressed to Dr
    66 NATURE [Nov. 22, r877 addressed to Dr. J annetaz, Secretaire-general, rue des the accuracy to which observers had attained. by the old Grands Augustins, 7, Paris, France; and all moneys sent method; but in the rude nature of the telescope itself in to Dr. Bioche, at the same address. the early times, before the introductio.n of the micrometer ; the modern accuracy has been arnved at step by step. THE MODERN TELESCOPE HE gain to astronomy from the discovery of the T telescope has been twofold. We. first, the. gain to physical astronomy from the magmficauon of obJects; and secondly, the gain to astronomy of position from the magnification, so to speak, of space, which enables minute ·portions of it to be most accurately quantified. FtG. 1.-A portion of the constellation Gemini seen with the naked eye. Looking back, nothing is more curious in the history of astronomy than the rooted objection which Revel and Let us see what the telescope does for us in the others showed to apply the telescope to the pointers and domain of that grand physical astronomy which deals pinnules of the instruments used in their day ; but doubt- with the number and appearances of the various bodies less we must look for the explanation of this not only in 1 which people space . FJG. 2.-The same region, as seeu through a large telescope. Let us, to begin with, try to see how the telescope helps the moon with a telescope of that magnifying power pretty us in the matter of observations of the sun.
    [Show full text]
  • Measuring Night Sky Brightness: Methods and Challenges
    Measuring night sky brightness: methods and challenges Andreas H¨anel1, Thomas Posch2, Salvador J. Ribas3,4, Martin Aub´e5, Dan Duriscoe6, Andreas Jechow7,13, Zolt´anKollath8, Dorien E. Lolkema9, Chadwick Moore6, Norbert Schmidt10, Henk Spoelstra11, G¨unther Wuchterl12, and Christopher C. M. Kyba13,7 1Planetarium Osnabr¨uck,Klaus-Strick-Weg 10, D-49082 Osnabr¨uck,Germany 2Universit¨atWien, Institut f¨urAstrophysik, T¨urkenschanzstraße 17, 1180 Wien, Austria tel: +43 1 4277 53800, e-mail: [email protected] (corresponding author) 3Parc Astron`omicMontsec, Comarcal de la Noguera, Pg. Angel Guimer`a28-30, 25600 Balaguer, Lleida, Spain 4Institut de Ci`encies del Cosmos (ICCUB), Universitat de Barcelona, C.Mart´ıi Franqu´es 1, 08028 Barcelona, Spain 5D´epartement de physique, C´egep de Sherbrooke, Sherbrooke, Qu´ebec, J1E 4K1, Canada 6Formerly with US National Park Service, Natural Sounds & Night Skies Division, 1201 Oakridge Dr, Suite 100, Fort Collins, CO 80525, USA 7Leibniz-Institute of Freshwater Ecology and Inland Fisheries, 12587 Berlin, Germany 8E¨otv¨osLor´andUniversity, Savaria Department of Physics, K´arolyi G´asp´ar t´er4, 9700 Szombathely, Hungary 9National Institute for Public Health and the Environment, 3720 Bilthoven, The Netherlands 10DDQ Apps, Webservices, Project Management, Maastricht, The Netherlands 11LightPollutionMonitoring.Net, Urb. Ve¨ınatVerneda 101 (Bustia 49), 17244 Cass`ade la Selva, Girona, Spain 12Kuffner-Sternwarte,Johann-Staud-Straße 10, A-1160 Wien, Austria 13Deutsches GeoForschungsZentrum Potsdam, Telegrafenberg, 14473 Potsdam, Germany Abstract Measuring the brightness of the night sky has become an increasingly impor- tant topic in recent years, as artificial lights and their scattering by the Earth’s atmosphere continue spreading around the globe.
    [Show full text]
  • AM205: Syllabus
    AM205: Data fitting for imaging Comet NEOWISE In late July 2020, Comet NEOWISE was visible from Earth. From a dark sky location, the comet was easily visible to the naked eye, and there were many superb photos that were taken showing the intricate structure of its tail. Chris has been fascinated by astronomy since an early age. His homewown of Keswick in the United Kingdom has very little light pollution, and he was able to appreciate won- ders of the night sky. However, from his current home near Central Square in Cambridge, Massachusetts there are high levels of light pollution and the sky usually appears a dim grey with all but the brightest stars washed out. On the Bortle scale that is used to measure light pollution [1], Cambridge ranks at roughly 7–8. Chris has a Fuji XT-4 digital camera, which has excellent image quality, but typical pictures of the night sky have a bright grey background. Figure1 shows a typical raw camera image, and it is difficult to make out any detail beyond the brightest stars. Further problems like aircraft lights and brightly lit clouds are also visible. As students of AM205, we can ask ourselves if it is possible to do better. The light pollution adds a smooth, but spatially varying, background to the image. Can we use our data fitting skills to subtract this out and reveal more detail? Figure 1: An example of the difficulty of night sky imaging from an urban area. This image with a 6.5 s exposure was taken near the MIT sports fields on August 11, 2020.
    [Show full text]