Photometry, from Greek photo- and -metry, is a technique used in astronomy, concerned with measuring the flux or intensity of light radiated by astronomical objects. This light is measured through a telescope using a photometer made using electronic devices such as a CCD photometer or a photoelectric photometer that converts light into an electric current by the photoelectric effect; when calibrated against standard stars of known intensity and colour, photometers can measure the brightness or apparent magnitude of celestial objects. The methods used to perform photometry depend on the wavelength regime under study. At its most basic, photometry is conducted by gathering light and passing it through specialized photometric optical bandpass filters, capturing and recording the light energy with a photosensitive instrument. Standard sets of passbands are defined to allow accurate comparison of observations. A more advanced technique is spectrophotometry, measured with a spectrophotometer and observes both of the amount of radiation and its detailed spectral distribution.
Photometry is used in the observation of variable stars, by various techniques such as, differential photometry that measuring the brightness of a target object and nearby stars in the starfield or relative photometry by comparing the brightness of the target object to stars with known fixed magnitudes. Using multiple bandpass filters with relative photometry is termed absolute photometry. A plot of magnitude against time produces a light curve, yielding considerable information about the physical process causing the brightness changes. Precision photoelectric photometers can measure starlight around 0.001 magnitude. The technique of surface photometry can be used with extended objects like planets, nebulae or galaxies that measures the apparent magnitude in terms of magnitudes per square arcsecond. Knowing the area of the object and the average intensity of light across the astronomical object determines the surface brightness in terms of magnitudes per square arcsecond, while integrating the total light of the extended object can calculate brightness in terms of its total magnitude, energy output or luminosity per unit surface area.
Photometers employ the use of specialised standard passband filters across the ultraviolet and infrared wavelengths of the electromagnetic spectrum. Any adopted set of filters with known light transmission properties is called a photometric system, allows the establishment of particular properties about stars and other types of astronomical objects. Several important systems are used, such as the UBV system, near infrared JHK or the Strömgren uvbyβ system. Photometry in the near-infrared through short-wavelength ultra-violet was done with a photoelectric photometer, an instrument that measured the light intensity of a single object by directing its light onto a photosensitive cell like a photomultiplier tube; these have been replaced with CCD cameras that can image multiple objects, although photoelectric photometers are still used in special situations, such as where fine time resolution is required. Modern photometric methods define magnitudes and colours of astronomical objects using electronic photometers viewed through standard coloured bandpass filters.
This differs from other expressions of apparent visual magnitude observed by the human eye or obtained by photography: that appear in older astronomical texts and catalogues. Magnitudes measured by photometers in some commonplace photometric systems are expressed with a capital letter. E.g.'V", "B", etc. Other magnitudes estimated by the human eye are expressed using lower case letters. E.g. "v", "b" or "p", etc. e.g. Visual magnitudes as mv, while photographic magnitudes are mph / mp or photovisual magnitudes mp or mpv. Hence, a 6th magnitude star might be stated as 6.0V, 6.0B, 6.0v or 6.0p. Because starlight is measured over a different range of wavelengths across the electromagnetic spectrum and are affected by different instrumental photometric sensitivities to light, they are not equivalent in numerical value. For example, apparent magnitude in the UBV system for the solar-like star 51 Pegasi is 5.46V, 6.16B or 6.39U, corresponding to magnitudes observed through each of the visual'V', blue'B' or ultraviolet'U' filters.
Magnitude differences between filters indicate colour differences and are related to temperature. Using B and V filters in the UBV system produces the B–V colour index. For 51 Pegasi, the B–V = 6.16 – 5.46 = +0.70, suggesting a yellow coloured star that agrees with its G2IV spectral type. Knowing the B–V results determines the star's surface temperature, finding an effective surface temperature of 5768±8 K. Another important application of colour indices is graphically plotting star's apparent magnitude against the B–V colour index; this forms the important relationships found between sets of stars in colour–magnitude diagrams, which for stars is the observed version of the Hertzsprung-Russell diagram. Photometric measurements of multiple objects obtained through two filters will show, for example in an open cluster, the comparative stellar evolution between the component stars or to determine the cluster's relative age. Due to the large number of different photometric systems adopted by astronomers, there are many expressions of magnitudes and their indices.
Each of these newer photometric systems, excluding UBV, UBVRI or JHK systems, assigns an upper or lower case letter to the filter used. E.g. Magnitudes used by Gaia are'G' or the Strömgren photometric system having
Foon Yew High School is the largest Chinese independent high school in Malaysia. It is the only Chinese independent high school with two campuses: one in Stulang Laut, the other in Kulai. Foon Yew High School has two semesters each year. An academic year begins in January and finishes at the end of November, with a near two-week holiday in June. Foon Yew High School is the largest Chinese independent high school in Malaysia in terms of both students and campus size; the main school, with its 13-acre campus, is located in Stulang Laut, Johor Bahru while the school's Kulai branch, with its 30-acre campus, is located in Taman Indahpura, Kulai. The school enrolls the most students among the Chinese independent high schools in Malaysia. In Jan 2007, there were 5326 registered students in the main campus and 2684 registered students in its Kulai campus. Foon Yew High School is named after a quote in the Doctrine of the Mean: "宽柔以教，不报无道，南方之强也，君子居之。" A Confucius statue stands at the centre of the main school campus.
A quote by Confucius can be found below the statue: 学而不思则罔，思而不学则殆。 The current principal is Ms. Tee Bee Tin. On 18 May 1913, Foon Yew Chinese Primary School was founded by Huang Xichu, Luo Yusheng, Zheng Yaji and Chen Yingxiang. During World War II, the school was forced to close down. After World War II, the school was re-constructed by Shi Liandui. In 1951, the school established Foon Yew High School. In 1963, the number of students reached 1500. In 1980, the school implemented an entrance examination for new students. There were over 4000 students in the school at the time. In 2005, the school's branch, Foon Yew-Kulai High School, in Kulai, Johor was opened. In 2015, Foon Yew High School-Kulai celebrated the school's 10th anniversary; the current students in both high schools had reached 12000. Penny Tai - a popular singer and songwriter in the Mandopop music arena Chen Hanwei - an actor from MediaCorp known as Singapore Broadcasting Corporation Yao Wenlong- an actor from MediaCorp known as Singapore Broadcasting Corporation Apple Hong - an actress from MediaCorp known as Singapore Broadcasting Corporation Chew Sin Huey - a singer, the first runner-up in the female category of Project SuperStar 2005 Dr. Boo Cheng Hau - a Johor state assemblyman of the political party DAP.
Won in the Skudai zone of the 12th Malaysia General Election over fellow Foon Yew Alumni Dr. Kee Keh Kooi - a professor in medicine faculty of Tsing Hua University, China; the only Malaysian-Chinese in the China "Tianzhou 1" research team Dato' Siow Kuang Ling - an inventor and medical surgeon. His inventions have won more than 20 awards from International Innovation competitions. Quek See Ling - a poet, Chinese ink painter and editor. Education in Malaysia "Johor Bahru Foon Yew High School 2007 new academic year ceremony", 3 January 2007. Accessed 26 April 2007. "2007 Foon Yew-Kulai High School new enrolled students". Accessed 26 April 2007. "Chinese version of the Doctrine of the Mean", Wikisource. Accessed 26 April 2007. Muller, Charles. "The Doctrine of the Mean", 23 March 2005. Accessed 26 April 2007. Foon Yew High School Foon Yew-Kulai High School Foon Yew Alumni Information Office Foon Yew Alumni Association
Penelope Skinner is a British playwright who came to prominence after her play Fucked was first produced in 2008 at the Old Red Lion Theatre and the Edinburgh Festival to huge critical acclaim and has had successive plays staged in London including at the Bush Theatre, National Theatre and Royal Court Theatre, where she is a member of the Young Writers Programme. Her play Eigengrau staged at the Bush Theatre in 2010 was a critical and box office hit and Skinner was nominated for the Evening Standard Award for Most Promising Playwright in 2010. Skinner's play The Village Bike was her first play to be staged at the Royal Court Theatre where it had a sell out, twice-extended run starring Romola Garai and directed by Joe Hill-Gibbins, winning her the George Devine Award and the Evening Standard Award for Most Promising Playwright in 2011. In 2011 she wrote episodes for the Channel 4 series Fresh Meat. In 2011, her play The Sound of Heavy Rain was produced by Paines Plough and Sheffield Theatres touring in Roundabout.
Her play Fred's Diner was staged at the Chichester Festival Theatre's pop-up stage, following which The Independent newspaper described Skinner as "Our leading young feminist writer."In 2013 Skinner co-wrote the screenplay for the film How I Live Now. 2018 Meek premiered at Traverse Theatre directed by Amy Hodge 2017 Linda Manhattan Theatre Club, New York.