... 2001 April 15 . Diffraction Spikes: When Stars Look Like Crosses . ... Light scatters away from the original destination point ending up elsewhere and appearing as " diffraction spikes ." These annoying spikes steal precious light from the central image and hide light from fainter, more interesting stars. Above , astronomers are more interested in the half-circled point near the image center, than the cool-looking diffraction spikes from the bright star at the bottom. ... About APOD | ...

... WFPC2 , HST , NASA Explanation: Unusual appendages around bright stars are commonplace, but never seem to be mentioned. ... First, a telescope brings starlight falling over a large area to a small area . ... Above , astronomers are more interested in the half-circled point near the image center, than the cool-looking diffraction spikes from the bright star at the bottom. ... NASA Official: Jay Norris. ... Publications with keywords: stars - diffraction spikes - astrophotography . ...

You Can Make Stellar Images Brighter . Articles | ... A few months ago I wrote an article titled "You Can’t Make Them Brighter". So why am I now writing that you can make them brighter. ... The image of a focused star is actually a small disk called the Airy disk, named after the 19 th century scientist Sir George Airy. ... For a given aperture, a smaller Airy disk means that the light is focused to a smaller disk and is therefore brighter. ... www.astronomy.net . About Astronomy Net | ...

... SEARCH ASP SITE: Match ALL words Match ANY word . ... ASP Conference Series . ... Accidental Astrophysics: The Devil's In the Magnitudes, Part II . ... The star second to the Sun in brilliance is Sirius. ... Recall the magnitude system, passed down to us through a hundred generations of sky watchers, as a means of quantifying stellar brightness ("Accidental Astrophysics," May/June, p. 9). ... Yes, it is a magnitude difference, but that difference is due to the distance between us and the star. ...

... Bad Astronomy . ... Bitesize Astronomy . ... Last week's Snack talked about how black holes can affect the environment around them in such a way as to be very bright . ... It's a common misconception that black holes always have matter swirling into them. ... As this matter gets closer and closer to the black hole it piles up and a large, fairly flat disk forms. This is called the accretion disk , because matter from this disk accretes (that is, falls in) on the black hole. ... 2008 Phil Plait. ...

... From Terry Moseley: "A very bright fireball was seen widely over Ireland, and even as far away as Liverpool, at about 00.30 on Sunday morning, 4 April. John McConnell saw it from Maghaberry, Co Antrim, and a woman saw it from her home in Newry, Co Down. The Liverpool observer reports that the fireball appeared at 30 - 40 degrees altitude in the western sky at 00:33 UT on 2009 April 05. ... I saw it) early Sunday morning at 00:32 BST. ... International Year of Astronomy, Ireland National Node . ...

Astronotes Armagh Planetarium's Stellar Blog! ... Space Flight . ... Earth Satellites . ... Leonid meteors seen from 13 km altitude aboard an aircraft during the 1999 Leonids Multi-Instrument Aircraft Campaign (Leonid-MAC). Comet Tempel-Tuttle provides the cometary debris for the Leonid meteor shower. ... Every 17-19 November Earth crosses Tempel-TuttleтАЩs orbit and the Leonids become visible. With clear, dark skies observers may see 10 to 15 Leonid meteors every hour on those mornings. ...

... The bright supernova (hereafter SN) in the galaxy NGC 4527 was first sighted by S. Knight (USA) on April 13.17UT at magnitude ~14.0v. The report of the sighting was subsequently forwarded by phone to the AAVSO. ... SN 1991T. The galaxy NGC 4527 is an Sb(s)II type galaxy with an apparent Blue magnitude of 11.32 (Shapley-Ames, 1981). ... An analysis of this event utilizing visual observations by amateurs, plus a light curve is presented.. ... THE LIGHT CURVE: . ... ISN SN 1991T web page . ...

... Bringing news from across the Universe to children all around the world . ... Have you ever walked down the street late a night and seen a point of light in the distance? ... This is because things look fainter when they're farther away. ... That s what astronomers did in 1995 when the Hubble Space Telescope was pointed at a region of the night sky about the size a tennis ball would look if it were a 100-metres away. ... One camera, called MUSE, was used to take a fresh look at the patch of sky. ...

... 2000 April 24 . Reflection Nebula M78 . ... Explanation: An eerie blue glow and ominous columns of dark dust highlight M78, a bright reflection nebula in the constellation of Orion . The dust not only absorbs light, but also reflects the light of several bright blue stars that formed recently in the nebula. ... M78 belongs to the larger Orion Molecular Cloud Complex that contains the Great Nebula in Orion and the Horsehead Nebula . ... About APOD | ...

... Current APO Weather . ... Search Site . ... Information for New Users . ... Technical Staff pages . Night Logs and Mailing Lists (maintained by APO) . ... Technical Documents and Database Search . ... Observer's Documentation and Procedures . ... Problem Reporting and APO Technical Documents Database Search . ... APO Drawing/Document Management Procedures . ... APO Technical Documents Database Search . Home Astrophysical Research Consortium . ... Mail Lists (maintained by APO) . ...

... WFC3 Data Handbook > Chapter 5: WFC3-UVIS Sources of Error > 5.5 Image Anomalies . ... Ghosts appear as images of the pupil formed from the light of a bright target in, or near the UVIS detector FOV. ... Further details concerning these ghosts may be found in WFC3 ISR 2007-09. ... Specifically, in full-frame, unbinned UVIS readouts, the CT level is ~2x10 -4 of the source when the target is in quadrants A or C and about 8x10 -5 when the target is in quadrants B or D ( WFC3 ISR 2009-03 ). ...

... This program was created for correlating chosen regions in the series of fts images. ... Chosen regions' . ... In this section the program counts the integral for each region of the grid for each image. ... As a matter of fact, the integral is total brightness of the region and it is counted by 'int_tabulated' IDL function. ... In addition, the program will show the count of the regions which correlate with the corresponding region (the brighter region means the bigger count) and its contour. ...

... More information on books, telescopes, clubs, etc. is available in the Getting Started section. ... For more information call 617-495-7461. Boston University Astronomy Department - Public telescopic observing is held every clear Wednesday night. ... Boston Museum of Science - For more information and admission prices call 617-723-2500. ... For information and admission prices call 508-929-2700. ... Springfield Telescope Makers , VT. ... Copyright (c) Amateur Telescope Makers of Boston, Inc. ...

Gratteri Crater, 4.3 miles (6.9 km) across, has a ray pattern whose most distant rays reach about 450 miles (600 km) and perhaps farther. Lunar rays appear bright, but GratteriтАЩs look dark because the image was taken at night by thermal infrared light. In the infrared, rocky areas are bright because they still hold daytime warmth. ... Unlike other ray craters, Gratteri occurred in ancient terrain and may be the source of the oldest Mars meteorite, ALH84001. ...

... The Pleiades star cluster, also known as the Seven Sisters and Messier 45, is a conspicuous object in the night sky with a prominent place in ancient mythology . ... The stars in the Pleiades are thought to have formed together around 100 million years ago, making them 1/50th the age of our sun, and they lie some 130 parsecs (425 light years ) away. ... Data for these stars are listed in a table below. ... Yes . ... WEBDA Pleiades cluster data . ... M45: The Pleiades Star Cluster (2007 November 18) ...

... 2004: . ... An increase in star brightness is followed by a decrease in asphericity and wind velocity to the point where stationary and even accreting fraction of the wind appears in extremely bright objects together with a flowing out fraction. ... Based on an analysis of observations obtained with BTA and on the published data it was found that degree of abnormality of energy distribution in continuum of magnetic chemically peculiar stars increases with an increase of their rotation period. ...

... ATNF Home . ... About ATNF overview . ... Australia Telescope Steering Committee . ... Murchison Radio-astronomy Observatory . ... Parkes radio telescope . ... Visiting Parkes radio telescope . ... Parkes radio telescope webcam . ... Distances to the Stars . ... Astronomers actually use a unit of distance called the parsec (pc) to express distances to other stars and galaxies. ... When we determine the distance to each of the bright stars in Crux however we see that their distances vary greatly. ...

... Circumstellar disc of beta Pictoris: constraints on grain properties from polarization. To appear in the Astronomy & Astrophysics . abs , src , ps ] . ... Dust influx to Titan from Hyperion . ... abs ] . ... Characteristics of bulges and disks in interacting galaxies . ... Dust grains around Herbig Ae/Be stars: porous, cometary-like grains? ... To appear in the Astronomy & Astrophysics Supplement . ... Finally, Links may lead you to more options (e.g. via the LANL preprint system). ...

... Spherical aberration, coma, and astigmatism are also easily observed using the star test. ... Off-axis images are complex. ... Fig. ... Diffraction by a circular aperture as a function of defocus for no aberration Airy Disk 1 wave defocus Less than 1 wave defocus Fig. ... Diffraction by a circular aperture as a function of defocus for third-order spherical aberration Paraxial Focus Small distance inside paraxial focus Moderate distance from marginal focus Immediate neighborhood of marginal focus Fig...