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Breaking Down the “Cosine Fourth Power Law”
Breaking Down The “Cosine Fourth Power Law” By Ronian Siew, inopticalsolutions.com Why are the corners of the field of view in the image captured by a camera lens usually darker than the center? For one thing, camera lenses by design often introduce “vignetting” into the image, which is the deliberate clipping of rays at the corners of the field of view in order to cut away excessive lens aberrations. But, it is also known that corner areas in an image can get dark even without vignetting, due in part to the so-called “cosine fourth power law.” 1 According to this “law,” when a lens projects the image of a uniform source onto a screen, in the absence of vignetting, the illumination flux density (i.e., the optical power per unit area) across the screen from the center to the edge varies according to the fourth power of the cosine of the angle between the optic axis and the oblique ray striking the screen. Actually, optical designers know this “law” does not apply generally to all lens conditions.2 – 10 Fundamental principles of optical radiative flux transfer in lens systems allow one to tune the illumination distribution across the image by varying lens design characteristics. In this article, we take a tour into the fascinating physics governing the illumination of images in lens systems. Relative Illumination In Lens Systems In lens design, one characterizes the illumination distribution across the screen where the image resides in terms of a quantity known as the lens’ relative illumination — the ratio of the irradiance (i.e., the power per unit area) at any off-axis position of the image to the irradiance at the center of the image. -
Cosmos: a Spacetime Odyssey (2014) Episode Scripts Based On
Cosmos: A SpaceTime Odyssey (2014) Episode Scripts Based on Cosmos: A Personal Voyage by Carl Sagan, Ann Druyan & Steven Soter Directed by Brannon Braga, Bill Pope & Ann Druyan Presented by Neil deGrasse Tyson Composer(s) Alan Silvestri Country of origin United States Original language(s) English No. of episodes 13 (List of episodes) 1 - Standing Up in the Milky Way 2 - Some of the Things That Molecules Do 3 - When Knowledge Conquered Fear 4 - A Sky Full of Ghosts 5 - Hiding In The Light 6 - Deeper, Deeper, Deeper Still 7 - The Clean Room 8 - Sisters of the Sun 9 - The Lost Worlds of Planet Earth 10 - The Electric Boy 11 - The Immortals 12 - The World Set Free 13 - Unafraid Of The Dark 1 - Standing Up in the Milky Way The cosmos is all there is, or ever was, or ever will be. Come with me. A generation ago, the astronomer Carl Sagan stood here and launched hundreds of millions of us on a great adventure: the exploration of the universe revealed by science. It's time to get going again. We're about to begin a journey that will take us from the infinitesimal to the infinite, from the dawn of time to the distant future. We'll explore galaxies and suns and worlds, surf the gravity waves of space-time, encounter beings that live in fire and ice, explore the planets of stars that never die, discover atoms as massive as suns and universes smaller than atoms. Cosmos is also a story about us. It's the saga of how wandering bands of hunters and gatherers found their way to the stars, one adventure with many heroes. -
Moving Pictures: the History of Early Cinema by Brian Manley
Discovery Guides Moving Pictures: The History of Early Cinema By Brian Manley Introduction The history of film cannot be credited to one individual as an oversimplification of any his- tory often tries to do. Each inventor added to the progress of other inventors, culminating in progress for the entire art and industry. Often masked in mystery and fable, the beginnings of film and the silent era of motion pictures are usually marked by a stigma of crudeness and naiveté, both on the audience's and filmmakers' parts. However, with the landmark depiction of a train hurtling toward and past the camera, the Lumière Brothers’ 1895 picture “La Sortie de l’Usine Lumière à Lyon” (“Workers Leaving the Lumière Factory”), was only one of a series of simultaneous artistic and technological breakthroughs that began to culminate at the end of the nineteenth century. These triumphs that began with the creation of a machine that captured moving images led to one of the most celebrated and distinctive art forms at the start of the 20th century. Audiences had already reveled in Magic Lantern, 1818, Musée des Arts et Métiers motion pictures through clever uses of slides http://en.wikipedia.org/wiki/File:Magic-lantern.jpg and mechanisms creating "moving photographs" with such 16th-century inventions as magic lanterns. These basic concepts, combined with trial and error and the desire of audiences across the world to see entertainment projected onto a large screen in front of them, birthed the movies. From the “actualities” of penny arcades, the idea of telling a story in order to draw larger crowds through the use of differing scenes began to formulate in the minds of early pioneers such as Georges Melies and Edwin S. -
American Scientist the Magazine of Sigma Xi, the Scientific Research Society
A reprint from American Scientist the magazine of Sigma Xi, The Scientific Research Society This reprint is provided for personal and noncommercial use. For any other use, please send a request to Permissions, American Scientist, P.O. Box 13975, Research Triangle Park, NC, 27709, U.S.A., or by electronic mail to [email protected]. ©Sigma Xi, The Scientific Research Society and other rightsholders Engineering Next Slide, Please Henry Petroski n the course of preparing lectures years—against strong opposition from Ibased on the material in my books As the Kodak some in the artistic community—that and columns, I developed during the simple projection devices were used by closing decades of the 20th century a the masters to trace in near exactness good-sized library of 35-millimeter Carousel begins its intricate images, including portraits, that slides. These show structures large and the free hand could not do with fidelity. small, ranging from bridges and build- slide into history, ings to pencils and paperclips. As re- The Magic Lantern cently as about five years ago, when I it joins a series of The most immediate antecedent of the indicated to a host that I would need modern slide projector was the magic the use of a projector during a talk, just previous devices used lantern, a device that might be thought about everyone understood that to mean of as a camera obscura in reverse. Instead a Kodak 35-mm slide projector (or its to add images to talks of squeezing a life-size image through a equivalent), and just about every venue pinhole to produce an inverted minia- had one readily available. -
Interstellar Spaceflight
SPACEFLIGHT TOMORROW Interstellar Can We Travel to Other Stars? Small self-replicating probes could be launched on interstellar journeys. Creating a galactic Internet may yield even greater benefits by Timothy Ferris iving as we do in technologically triumphant times, we are inclined to NEAREST STARS to the solar system view interstellar spaceflight as a technical challenge, like breaking the are depicted in this view of the Milky Way galaxy as seen from 500 light- Lsound barrier or climbing Mount Everest—something that will no years above the galactic plane. The doubt be difficult but feasible, given the right resources and resourcefulness. green lines between the stars (inset) represent high-bandwidth radio This view has much to recommend it. Unmanned interstellar travel has, in a sense, beams in a hypothetical communi- already been achieved, by the Pioneer 10 and 11 and Voyager 1 and 2 probes, which cations network linking alien civiliza- were accelerated by their close encounters with Jupiter to speeds in excess of the sun’s tions. Such an interstellar network escape velocity and are outward-bound forever. By interstellar standards, these space- would allow intelligent species to craft are slow: Voyager 1, the speediest of the four at 62,000 kilometers per hour share knowledge without incurring (39,000 miles per hour), will wander for several tens of thousands of years before it the tremendous expense of traveling encounters another star. But the Wright brothers’ first airplane wasn’t particularly to other stars. speedy either. A manned interstellar spacecraft that improved on Voyager’s velocity by the same 1,000-fold increment by which Voyager improved on the Kitty Hawk flights could reach nearby stars in a matter of decades, if a way could be found to pay its exorbitant fuel bill. -
Lecture 4A: Cameras
CS6670: Computer Vision Noah Snavely Lecture 4a: Cameras Source: S. Lazebnik Reading • Szeliski chapter 2.2.3, 2.3 Image formation • Let’s design a camera – Idea 1: put a piece of film in front of an object – Do we get a reasonable image? Pinhole camera • Add a barrier to block off most of the rays – This reduces blurring – The opening known as the aperture – How does this transform the image? Camera Obscura • Basic principle known to Mozi (470‐390 BC), Aristotle (384‐322 BC) • Drawing aid for artists: described by Leonardo da Vinci (1452‐1519) Gemma Frisius, 1558 Source: A. Efros Camera Obscura Home‐made pinhole camera Why so blurry? Slide by A. Efros http://www.debevec.org/Pinhole/ Shrinking the aperture • Why not make the aperture as small as possible? • Less light gets through • Diffraction effects... Shrinking the aperture Adding a lens “circle of confusion” • A lens focuses light onto the film – There is a specific distance at which objects are “in focus” • other points project to a “circle of confusion” in the image – Changing the shape of the lens changes this distance Lenses F focal point • A lens focuses parallel rays onto a single focal point – focal point at a distance f beyond the plane of the lens (the focal length) • f is a function of the shape and index of refraction of the lens – Aperture restricts the range of rays • aperture may be on either side of the lens – Lenses are typically spherical (easier to produce) Thin lenses • Thin lens equation: – Any object point satisfying this equation is in focus – What is the shape -
Device-Independent Representation of Photometric Properties of a Camera
CVPR CVPR #**** #**** CVPR 2010 Submission #****. CONFIDENTIAL REVIEW COPY. DO NOT DISTRIBUTE. 000 054 001 055 002 056 003 Device-Independent Representation of Photometric Properties of a Camera 057 004 058 005 059 006 Anonymous CVPR submission 060 007 061 008 062 009 Paper ID **** 063 010 064 011 065 012 Abstract era change smoothly across different device configurations. 066 013 The primary advantages of this representation are the fol- 067 014 In this paper we propose a compact device-independent lowing: (a) generation of an accurate representation using 068 015 representation of the photometric properties of a camera, the measured photometric properties at a few device config- 069 016 especially the vignetting effect. This representation can urations obtained by sparsely sampling the device settings 070 017 be computed by recovering the photometric parameters at space; (b) accurate prediction of the photometric parame- 071 018 sparsely sampled device configurations(defined by aper- ters from this representation at unsampled device configu- 072 019 ture, focal length and so on). More importantly, this can rations. To the best of our knowledge, we present the first 073 020 then be used for accurate prediction of the photometric device independent representation of photometric proper- 074 021 parameters at other new device configurations where they ties of cameras which has the capability of predicting device 075 022 have not been measured. parameters at configurations where it was not measured. 076 023 Our device independent representation opens up the op- 077 024 portunity of factory calibration of the camera and the data 078 025 1. Introduction then being stored in the camera itself. -
NASA Celebrates Voyager and NASA IBEX Study Reveals New Dynamics of the Heliospheric Boundary
NASA Celebrates Voyager and NASA IBEX Study Reveals New Dynamics of the Heliospheric Boundary September 5, 2017 marked the 40th anniversary of the 1977 Voyager 1 spacecraft launch. Voyager 2 was launched on August 20, 1977. Although Voyager 1 was launched a few weeks after Voyager 2, it quickly sped ahead of Voyager 2 in space and today is the farthest spacecraft from Earth at 13 billion miles. Voyager 2 is the second farthest, with both spacecraft venturing where no human-made object has ever gone: into interstellar space. Voyager 1 is already outside the heliosphere. Voyager 2 is not far behind, approaching the heliopause, the critical boundary separating the solar wind from interstellar space. The NASA Heliophysics Interstellar Boundary Explorer (IBEX) mission, launched in 2008, is the first spacecraft designed to collect data across the entire sky about the heliosphere and the solar system’s boundary with interstellar space. A recent analysis of IBEX data has shown how the heliosphere “reacts” to the changes in polar coronal holes, which change in size with the 11-year solar cycle. A study by a team of scientists led by Dr. Eric Zirnstein of Princeton University analyzed IBEX observations of Energetic Neutral Atoms (ENAs) collected between 2009 and 2015 over a range of energies (speeds of ~350 to 900 km/s). The team was able to track the Sun’s polar winds as they traveled out to the outer heliosphere, where they interacted with hydrogen atoms, creating ENA’s speeding back into the heliosphere towards the Sun. Analysis of IBEX data reveals it takes the solar wind near the Sun around two to three years to travel out to the heliosphere and then back toward the Sun to be seen in the data as ENAs. -
Single-Image Vignetting Correction Using Radial Gradient Symmetry
Single-Image Vignetting Correction Using Radial Gradient Symmetry Yuanjie Zheng1 Jingyi Yu1 Sing Bing Kang2 Stephen Lin3 Chandra Kambhamettu1 1 University of Delaware, Newark, DE, USA {zheng,yu,chandra}@eecis.udel.edu 2 Microsoft Research, Redmond, WA, USA [email protected] 3 Microsoft Research Asia, Beijing, P.R. China [email protected] Abstract lenge is to differentiate the global intensity variation of vi- gnetting from those caused by local texture and lighting. In this paper, we present a novel single-image vignetting Zheng et al.[25] treat intensity variation caused by texture method based on the symmetric distribution of the radial as “noise”; as such, they require some form of robust outlier gradient (RG). The radial gradient is the image gradient rejection in fitting the vignetting function. They also require along the radial direction with respect to the image center. segmentation and must explicitly account for local shading. We show that the RG distribution for natural images with- All these are susceptible to errors. out vignetting is generally symmetric. However, this dis- We are also interested in vignetting correction using a tribution is skewed by vignetting. We develop two variants single image. Our proposed approach is fundamentally dif- of this technique, both of which remove vignetting by min- ferent from Zheng et al.’s—we rely on the property of sym- imizing asymmetry of the RG distribution. Compared with metry of the radial gradient distribution. (By radial gradient, prior approaches to single-image vignetting correction, our we mean the gradient along the radial direction with respect method does not require segmentation and the results are to the image center.) We show that the radial gradient dis- generally better. -
Photographic Printing Enlarger
Photographic printing From Wikipedia, the free encyclopedia Photographic printing is the process of producing a final image on paper for viewing, using chemically sensitized paper. The paper is exposed to a photographic negative, a positive transparency (or slide), or a digital image file projected using an enlarger or digital exposure unit such as a LightJet printer. Alternatively, the negative or transparency may be placed atop the paper and directly exposed, creating a contact print. Photographs are more commonly printed on plain paper, for example by a color printer, but this is not considered "photographic printing". Following exposure, the paper is processed to reveal and make permanent the latent image. Printing on black-and-white paper The process consists of four major steps, performed in a photographic darkroom or within an automated photo printing machine. These steps are: Exposure of the image onto the sensitized paper using a contact printer or enlarger; Processing of the latent image using the following chemical process: o Development of the exposed image reduces the silver halide in the latent image to metallic silver; o Stopping development by neutralising, diluting or removing the developing chemicals; o Fixing the image by dissolving undeveloped silver halide from the light-sensitive emulsion: o Washing thoroughly to remove processing chemicals protects the finished print from fading and deterioration. Optionally, after fixing, the print is treated with a hypo clearing agent to ensure complete removal of the fixer, which would otherwise compromise the long term stability of the image. Prints can be chemically toned or hand coloured after processing.[ Enlarger From Wikipedia, the free encyclopedia An enlarger is a specialized transparency projector used to produce photographic prints from film or glass negatives using the gelatin silver process, or from transparencies. -
Dr. Kevin Grazier
Carl Sagan Center for Earth and Space Science Education Dr. Kevin Grazier Planetary Scientist NASA Jet Propulsion Laboratory Research Specialty: Large scale computational simulations of the Solar System Comfortable with the following age ranges: all Comfortable with the following audience sizes: all Dr. Kevin Grazier is a planetary scientist at NASA’s Jet Propulsion Laboratory (JPL). He did his doctoral research in planetary physics at UCLA, performing long-term large-scale computer simulations of early Solar System evolution. He started at JPL in 1995 as an academic part-time student, finishing his Ph.D. dissertation in 1997. At JPL, Dr. Grazier has written mission planning and analysis software that won JPL- and NASA-wide awards. He currently holds the duel titles of Investigation Scientist and Science Planning Engineer for the Cassini/Huygens Mission to Saturn and Titan. Dr. Grazier also continues research involving computer simulations of Solar System dynamics, evolution, and chaos with collaborators at UCLA, Los Alamos National Laboratory, Purdue University, and the University of Auckland. In addition to his JPL duties, Dr. Grazier teaches classes in basic astronomy, planetary science, cosmology, and the search for extraterrestrial life at UCLA and Santa Monica College. On a lighter note, Dr. Grazier also currently serves as the science advisor for the PBS educational animated series The Zula Patrol, and also for the SciFi Channel series Battlestar Galactica. Presentation Overviews and AV Requirements: Classroom Visits Our Solar System Grades K-6 What do the planets look like, and what makes each planet special? We examine each planet in the Solar System, and answer some of these questions. -
The Farthest — Voyager in Space
Q2 3 Program Guide KENW-TV/FM Eastern New Mexico University August 2017 The Farthest — Voyager in Space 1 When to watch from Channel 3-2 – August 2017 A to Z listings for 3-1 are on pages 18 & 19 American Woodshop – Saturdays, 6:30 a.m.; Thursdays, 11:00 a.m. Nova (continued) – America’s Heartland – Saturdays, 6:30 p.m. “Emperor’s Ghost Army” – Wednesday, 16th, 8:00 p.m.; America’s Test Kitchen – Saturdays, 7:30 a.m.; Saturday, 19th, 10:00 p.m.; Sunday, 20th, 12:30 a.m. Mondays, 11:30 a.m. (ends 14th) “Eclipse Over America” – Monday, 21st, 8:00 p.m.; Antiques Roadshow – Wednesday, 23rd, 7:00 p.m.; Saturday, 26th, 10:00 p.m.; Mondays, 7:00 p.m. (except 7th)/8:00 p.m. (except 7th, 21st)/11:00 p.m.; Sunday, 28th, 12:00 midnight Sundays, 7:00 a.m. “Zeppelin Terror Attack” – Wednesday, 20th, 8:00 p.m. Are You Being Served? Again! – Saturdays, 8:00 p.m. (19th, 26th only) P. Allen Smith’s Garden Home – Saturdays, 10:00 a.m. (except 12th) Ask This Old House – Saturdays, 4:00 p.m. (except 5th) Painting and Travel – Sundays, 6:00 a.m. (begins 13th) Austin City Limits – Paint This with Jerry Yarnell – Saturdays, 11:00 a.m. (except 12th) Saturdays, 9:00 p.m. (except 5th, 12th)/12:00 midnight PBS NewsHour – Weekdays, 6:00 p.m./12:00 midnight BBC World News – Weekdays, 6:30 a.m./4:30 p.m.; Fridays, 5:00 p.m.