5/26/2023 0 Comments Star chart date![]() ![]() Generally every half month you have to remove one hour from the clock and it is identically valid. Or it could be the sky at 21h in 14 days or 20h in a month. Just as you state: it could be from 22h today. OLD ANSWER where the time was not yet given:Ī star chart is not unique, it's ambiguous for date vs. Depending on accuracy and possibly further details given in the task, you will also have to consider the equation of time. You then have to find the date where the sidereal time matches your given mean solar time. Given your chart, it's no problem as it shows the sky for a location near or even exactly at the equator.Īs it's a question from a competition I will only sketch the path briefly: The stellar coordinates allows you to calculate the local hour angle of it and from that the sidereal time. You need to obtain the coordinates of a well-recognized star in equatorial coordinates (right ascension and declination), not too near the celestial pole. The other principal directions follow from that. They must have done something very clever.įirst determine the North (South) direction by drawing a line from the center through Polaris (Sigma Octantis). The celestial equator, the ecliptic, or the galactic plane?Īnd you might want to figure out how ancient astronomers figured out which constellations the Sun was in at a specific date, and even it's coordinates, if they couldn't see any stars near the Sun during daylight. You need to figure out what the dotted line represents. I am not very good a recognizing constellations but I do recognize a few. So you need to recognize as many of the constellations in the sky chart as you can. ![]() If stars at one edge of the chart are at the norther horizon at that time and date, stars at the opposite edge of the chart will be at the southern horizon at that time and date. If stars at one edge of the charat will be at the eastern horizon at that time and date, stars on the opposite side of the chart will be at the western horizon at that time and date. Stars and constellations about halfway between the center and the edge will be about 45 degress above the horizon. Stars and constellations in the center of the chart will be near the zenith of the sky at that time and date. Stars and constellations near the edges of the sky chart will be low on the horizon at that time and date. ![]() So you need to recognize some of the stars and constellations in the sky chart. Thus the hemisphere which once faceed toward the Sun will now face away from the Sun and it will be possible to see stars in the night time in that hemisphere, while the hemisphere of the sky which used to face away from the Sun will now face toward the Sun and it will be impossible to see stars in the day time in that hemisphere.Īs the Earth orbits the Sun, the stars visible at night slowly change, until after 6 months a whole different half of the sky is visible at night. So today one hemisphere of the sky will pointed toward the Sun, and it will be imposible to see stars in the daylight in that hemisphere, while the opposite hemisphere of the sky will be pointed away from the Sun and with will be possible to see stars in the night time in that hemisphere.Īnd 6 months from now the Earth will be on the opposite side of the Sun. It takes one year to orbit around the sun. The night sky is the hemisphere of the sky which is pointed away from the Sun. There may be other questions about the chart that relate to it. The dotted line has nothing to do with this specific problem. Even if you're not competing, keep in mind this is a public forum. Considering that the Olympiad is a competition, I'm sure that the rules prohibit getting the answer from a consultant. That should be all you need to solve the problem. You'll have to wade through some astrology to find the one you need. Those two references are both obvious if you look at an online star chart. The star furthest right in Casseopeia is very close to the vernal equinox, also known as the first point of Aries, which is the right ascension 0 degree reference. The constellation appropriately labeled W is Casseopeia. (Orion is the constellation labeled B.) North is, therefore, the point labeled 2. The tip-off is that a line between them passes through Orion, the top-right star in Orion's belt, which is very close to the celestial equator. The way the star chart is drawn, the points labeled 1 and 3 are on the celestial equator, the 0 degree declination reference. ![]()
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