![]() Yet, simply using a standard value assumes the true conditions at these disparately different sites are the same. Air behaves very differently, say, on a still January morning over the Great Lakes versus a hot dusty July morning off the west coast of Africa. However, this value is an approximation, and does not account for local meteorological conditions. Wilson notes in the study that this value is cited as far back as 1865, and its use may go all the way back to that 17 th century master of optics, Isaac Newton. ![]() ![]() Most standard sunrise calculations assume a refraction angle of 34′ arcminutes, a little larger than the apparent diameter of the Sun. Of course, your actual horizon is probably cluttered with foreground objects that the Sun needs to clear, unless you live on a remote mountaintop or are lucky enough to observe sunrise and sunset from the beach. Most calculations assume local sunrise and sunset time as when the center of the Sun’s disk clears the horizon. This size also changes very slightly from perihelion in January to aphelion in July, as the Sun seems to grow then shrink from a value of 31.6′ 32.7′ arc minutes. Also, like the Moon, the Sun’s apparent diameter is about half a degree across, meaning you could line the local horizon with 720 Suns end to end, or 180 Suns from horizon to zenith. Along with the Moon, the Sun is one of the few celestial objects that is large and close enough to appear as more than a point of light to the naked eye. Air bends light, meaning we see the Sun slightly offset from its true position on the horizon due to the atmosphere. If we lived on an airless word, the calculated and observed moment of sunrise would be easy… but as air-breathing mammals, we’d have other problems to contend with. Follow us on Twitter (opens in new tab) and on Facebook (opens in new tab). He writes about astronomy for Natural History magazine (opens in new tab), the Farmers' Almanac (opens in new tab) and other publications. Saturn's rings open to 15 degrees - the most they'll be tipped until 2027.Įditor's Note: If you snap a photo of the planets in September and would like to share it with 's readers, send your photo(s), comments, and your name and location to Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium (opens in new tab). Saturn shines markedly brighter than the 1st-magnitude bluish-white star Fomalhaut, which sparkles 20 degrees to the lower left. The ringed world is an easy and obvious sight in the evening sky a bright yellow-white starlike object in the southeast at nightfall and in the south during the mid-to-late evening. Saturn appears a half dozen degrees to the moon's upper right on the evening of Oct. (Image credit: Starry Night Software) (opens in new tab) ![]() Saturn's rings are now about as open as we'll see them until 2027. Related: Best telescopes for seeing planets 2022 Jupiter ![]() This month, as the distance from Mars decreases from 73 to 58 million miles (117 to 93 million km), it nearly doubles in brightness from magnitude minus 0.6 to minus 1.2, as we hurtle toward it at an average speed of 5.5 miles (8.8 km) per second. Throughout October Mars is positioned between the horns of Taurus the Bull about 10 to 15 degrees to the northeast of Aldebaran, which it greatly outshines, with the Pleiades looking on. But at the end of the month, it rises at around 8:25 p.m. local daylight time at the beginning of October and gets 30 degrees up, high enough for excellent observing, around 1 a.m. It rises well north of east around 10 p.m. The Red Planet is the planetary superstar this fall, but we still have to wait up a bit for it. Mars will be located about 3 degrees to the moon's lower right. Mars shining with a brilliant fiery orange light will be readily visible as the waning gibbous moon rises during the late evening hours of Oct. Mars will continue to gain in brilliance from now through early December. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |