... Deriving the sine or cosine of an arbitrary angle takes a bit more math than is covered here. ... Note first of all that a right-angled triangle contains two angles. ... Because the side opposite to A is the one adjacent to (90њ- A), it follows that the sine of one angle is the cosine of the other, and vice versa: . ... Consider the triangle PQR (drawing) with all three angles equal to 60њ. ... If we want the angle A to grow in equal steps of 15 o , we still need the sine and cosine of 15њ and 75њ. ...

Hipparchus (and possibly Aristarchus before him) also derived the Moon's distance from the duration of a lunar eclipse . Because the Earth casts a much larger shadow than the Moon, such an eclipse usually darkens the entire Moon, for several hours. ... If the Sun is assumed to be very distant, and if the Moon crosses the middle of the shadow (if not, corrections must be made), the width of the shadow is expected to be about 2r , twice the Earth's radius r . ... Last updated 4 February 1999 Moon. ...

... Posts tagged ?signal processing? ... Posted by hlee . ... Category: Algorithms , arXiv , Cross-Cultural , Data Processing , Fitting , Imaging , Methods , Quotes , Spectral , Stat , Uncertainty | ... ArXiv] 2nd week, Mar. ... Algorithms arXiv Astro Bad AstroStat Bayesian CHASC Cross-Cultural Data Processing Fitting Frequentist Galaxies gamma-ray High-Energy Imaging Jargon Job Languages MC MCMC Meta Methods Misc News Nuggets Objects Optical Physics Quotes Spectral Stars Stat Timing Uncertainty X-ray ....

Astronotes Armagh Planetarium's Stellar Blog! ... Armagh Planetarium . ... Stars . Exoplanets . ... Space Flight . ... Posted on February 3, 2011 | No Comments Kepler-11 is an amazing, newly-discovered system of exoplanets. ... Continue Reading.. ... No Comments Don Pollacco, a research astronomer at Queens University Belfast, came to Armagh Planetarium to give a fascinating talk on exoplanets in January 2011. ... Posted on November 29, 2010 | ... Posted on September 22, 2010 | ...

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General Forum Message . Forums: . ... Post . ... Here Is Another Link To M13 . ... Post Message | ... I have put the image of M13 on my home Web site - along with another image of M13 (not sure where it's from, I think SEDs). http://mysite.verizon.net/respud62/id7.html . ... www.astronomy.net . About Astronomy Net | Advertise on Astronomy Net | ... Forum posts are Copyright their authors as specified in the heading above the post. "dbHTML," "AstroGuide," "ASTRONOMY.NET" & "VA.NET" . ...

... The Amateur Telescope Makers of Boston, Inc. ATMoB) is an amateur astronomy club devoted to telescope making, observing, and studying the heavens. ... In 1973, the Bond Astronomical Society, another long-standing club, merged with the ATMoB making the club one of the oldest and largest general interest astronomy clubs in the country. ... The Amateur Telescope Makers of Boston, Inc. is an IRS designated 501(c)3 public charity organization. ... Copyright (c) Amateur Telescope Makers of Boston, Inc. ...