isros propsed aditya mission study magellanic clouds.
isros propsed aditya mission study magellanic clouds.
which celestial body will isros propsed aditya mission study?
magellanic clouds
longitude by chronometer is a method, in navigation, of determining longitude using a marine chronometer, which was developed by john harrison during the first half of the eighteenth century. it is an astronomical method of calculating the longitude at which a position line, drawn from a sight by sextant of any celestial body, crosses the observer's assumed latitude. in order to calculate the position line, the time of the sight must be known so that the celestial position i.e. the greenwich hour angle (celestial longitude - measured in a westerly direction from greenwich) and declination (celestial latitude - measured north or south of the equational or celestial equator), of the observed celestial body is known. all that can be derived from a single sight is a single position line, which can be achieved at any time during daylight when both the sea horizon and the sun are visible. to achieve a fix, more than one celestial body and the sea horizon must be visible. this is usually only possible at dawn and dusk.
longitude by chronometer
the measured angle between the celestial body and the visible horizon is directly related to the distance between the celestial body's gp and the observer's position. after some computations, referred to as sight reduction, this measurement is used to plot a line of position (lop) on a navigational chart or plotting work sheet, the observer's position being somewhere on that line. (the lop is actually a short segment of a very large circle on earth that surrounds the gp of the observed celestial body. an observer located anywhere on the circumference of this circle on earth, measuring the angle of the same celestial body above the horizon at that instant of time, would observe that body to be at the same angle above the horizon.) sights on two celestial bodies give two such lines on the chart, intersecting at the observer's position (actually, the two circles would result in two points of intersection arising from sights on two stars described above, but one can be discarded since it will be far from the estimated position—see the figure at example below). most navigators will use sights of three to five stars, if available, since that will result in only one common intersection and minimizes the chance of error. that premise is the basis for the most commonly used method of celestial navigation, referred to as the 'altitude-intercept method'.
celestial navigation