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A little check please
Hi guys. Well first of all, I have to say that after years of thinking that
I know one of the most common things, I just found out that I actually don't so that's why I am freaked out and require a check just to see if I am right for these basic astronomy questions. All this time I knew that the lines of longitude stretch from N to S and lines of latitude stretch from E to W. Then I just discovered that when latitude is measured, it's measured in a way that I thought that longitude was measured, meaning the measurement of altitude would be like 20* N and for longitude it would be like 64* E. It still doesn't make sense to me, why do you have these lines to go from N to S yet they measure coordinates in E and W. Anyhow here is my assignment, so can someone tell me if I am right or not. Thanks. Given resources: It's spring equinox, the Sun is on my meridian at 75* in the S, my UT clock says it 22:00 What is my longitude, latitude and where should I go in order to go to some land mass, instead of ice. 2. It's spring equinox meaning that the Sun's ecliptic will cross with the celestial equator on the celestial sphere. Since I have a watch, both my day and my night will last 12 hours each equally on this day, and today's date is most likely to be March 21. The Sun is on my meridian at altitude of 75* south, meaning that it's noon (12 p.m.) where I am standing at, and my latitude is 75* south. My watch, which is set to universal time, says it 's 22:00 meaning it's 10 p.m., so I must be behind 10 hours. This means that my longitude is 10hr times 15*/hr = 150* west of the prime meridian in Greenwich. My altitude is 75* south, meaning that my latitude is 75* south as well. Since I have a little map beside me, and since I have to sail to the nearest land, I should set sail northeast to Venezuela in South America. Thank you. |
#2
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For the land part, I meant Chile not Venezuela.
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#3
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For the land part, I meant Chile not Venezuela.
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#4
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"Zarkovic" wrote in news:y3Keb.2484$9l5.730@pd7tw2no:
Hi guys. Well first of all, I have to say that after years of thinking that I know one of the most common things, I just found out that I actually don't so that's why I am freaked out and require a check just to see if I am right for these basic astronomy questions. All this time I knew that the lines of longitude stretch from N to S and lines of latitude stretch from E to W. Then I just discovered that when latitude is measured, it's measured in a way that I thought that longitude was measured, meaning the measurement of altitude would be like 20* N and for longitude it would be like 64* E. Altitude is the angular measurement from your local horizon towards your local zenith. Azimuth is the compass bearing around your local horizon. The celestial equivalent to latitude and longitude are declination and right ascension. Declination is equivalent to latitude. i.e it is expressed in degrees north or south of the celestial equator, versus degress north or south of the Earth's equator. (The celestial equator is just the Earth's equator projected into the sky). Right ascension is similar to longitude but it is measured in time rather than degrees. I.e 24 hours versus 180 degrees east or west of Greenwich. The other difference is the start position (zero hours) is not measured from a point on the Earth's surface but from a point in the sky. In particular RA = 0, Dec = 0 is taken as the point on the celestial equator that the Sun crosses at the moment of the Vernal equinox (i.e marks the Northern hemisphere spring equinox). This point is sometimes just referred to as the Vernal Equinox but is also called "The first point of Aries". This is a historic definition as the Vernal Equinox is currently in Pisces due to the precession that has occurred since Ptolemy's day. It takes about 26,000 years for the Vernal Equinox to do a complete circuit. This is why the RA and DEC of a star are always only valid for a specific epoch. If you know what epoch (date) the RA and DEC were specified for, you can adjust (precess) the coordinates for the current date. Most planetarium programs do that automatically. Have a go at your homework question yourself :-). Llanzlan. SNIP |
#5
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"Zarkovic" wrote in news:y3Keb.2484$9l5.730@pd7tw2no:
Hi guys. Well first of all, I have to say that after years of thinking that I know one of the most common things, I just found out that I actually don't so that's why I am freaked out and require a check just to see if I am right for these basic astronomy questions. All this time I knew that the lines of longitude stretch from N to S and lines of latitude stretch from E to W. Then I just discovered that when latitude is measured, it's measured in a way that I thought that longitude was measured, meaning the measurement of altitude would be like 20* N and for longitude it would be like 64* E. Altitude is the angular measurement from your local horizon towards your local zenith. Azimuth is the compass bearing around your local horizon. The celestial equivalent to latitude and longitude are declination and right ascension. Declination is equivalent to latitude. i.e it is expressed in degrees north or south of the celestial equator, versus degress north or south of the Earth's equator. (The celestial equator is just the Earth's equator projected into the sky). Right ascension is similar to longitude but it is measured in time rather than degrees. I.e 24 hours versus 180 degrees east or west of Greenwich. The other difference is the start position (zero hours) is not measured from a point on the Earth's surface but from a point in the sky. In particular RA = 0, Dec = 0 is taken as the point on the celestial equator that the Sun crosses at the moment of the Vernal equinox (i.e marks the Northern hemisphere spring equinox). This point is sometimes just referred to as the Vernal Equinox but is also called "The first point of Aries". This is a historic definition as the Vernal Equinox is currently in Pisces due to the precession that has occurred since Ptolemy's day. It takes about 26,000 years for the Vernal Equinox to do a complete circuit. This is why the RA and DEC of a star are always only valid for a specific epoch. If you know what epoch (date) the RA and DEC were specified for, you can adjust (precess) the coordinates for the current date. Most planetarium programs do that automatically. Have a go at your homework question yourself :-). Llanzlan. SNIP |
#6
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Only one line of latitude is a great circle, meaning that its center
coincides with the center of the earth, and that is the zero degree line, or the equator. Every line of longitude is, however, a great circle, again with its center coincident with the center of the earth. Latitude varies from 90 deg N, through 0 deg at the equator, to 90 deg S. These lines form a locus of points that coincide with the earth's axis. Longitude varies from Greenwich, 0 deg, to 180 deg at the International Date Line, back to 0 deg. Hope this helped, although it didn't assist with the homework. . . Neal "Zarkovic" wrote in message news:y3Keb.2484$9l5.730@pd7tw2no... Hi guys. Well first of all, I have to say that after years of thinking that I know one of the most common things, I just found out that I actually don't so that's why I am freaked out and require a check just to see if I am right for these basic astronomy questions. All this time I knew that the lines of longitude stretch from N to S and lines of latitude stretch from E to W. Then I just discovered that when latitude is measured, it's measured in a way that I thought that longitude was measured, meaning the measurement of altitude would be like 20* N and for longitude it would be like 64* E. It still doesn't make sense to me, why do you have these lines to go from N to S yet they measure coordinates in E and W. Anyhow here is my assignment, so can someone tell me if I am right or not. Thanks. Given resources: It's spring equinox, the Sun is on my meridian at 75* in the S, my UT clock says it 22:00 What is my longitude, latitude and where should I go in order to go to some land mass, instead of ice. 2. It's spring equinox meaning that the Sun's ecliptic will cross with the celestial equator on the celestial sphere. Since I have a watch, both my day and my night will last 12 hours each equally on this day, and today's date is most likely to be March 21. The Sun is on my meridian at altitude of 75* south, meaning that it's noon (12 p.m.) where I am standing at, and my latitude is 75* south. My watch, which is set to universal time, says it 's 22:00 meaning it's 10 p.m., so I must be behind 10 hours. This means that my longitude is 10hr times 15*/hr = 150* west of the prime meridian in Greenwich. My altitude is 75* south, meaning that my latitude is 75* south as well. Since I have a little map beside me, and since I have to sail to the nearest land, I should set sail northeast to Venezuela in South America. Thank you. |
#7
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Only one line of latitude is a great circle, meaning that its center
coincides with the center of the earth, and that is the zero degree line, or the equator. Every line of longitude is, however, a great circle, again with its center coincident with the center of the earth. Latitude varies from 90 deg N, through 0 deg at the equator, to 90 deg S. These lines form a locus of points that coincide with the earth's axis. Longitude varies from Greenwich, 0 deg, to 180 deg at the International Date Line, back to 0 deg. Hope this helped, although it didn't assist with the homework. . . Neal "Zarkovic" wrote in message news:y3Keb.2484$9l5.730@pd7tw2no... Hi guys. Well first of all, I have to say that after years of thinking that I know one of the most common things, I just found out that I actually don't so that's why I am freaked out and require a check just to see if I am right for these basic astronomy questions. All this time I knew that the lines of longitude stretch from N to S and lines of latitude stretch from E to W. Then I just discovered that when latitude is measured, it's measured in a way that I thought that longitude was measured, meaning the measurement of altitude would be like 20* N and for longitude it would be like 64* E. It still doesn't make sense to me, why do you have these lines to go from N to S yet they measure coordinates in E and W. Anyhow here is my assignment, so can someone tell me if I am right or not. Thanks. Given resources: It's spring equinox, the Sun is on my meridian at 75* in the S, my UT clock says it 22:00 What is my longitude, latitude and where should I go in order to go to some land mass, instead of ice. 2. It's spring equinox meaning that the Sun's ecliptic will cross with the celestial equator on the celestial sphere. Since I have a watch, both my day and my night will last 12 hours each equally on this day, and today's date is most likely to be March 21. The Sun is on my meridian at altitude of 75* south, meaning that it's noon (12 p.m.) where I am standing at, and my latitude is 75* south. My watch, which is set to universal time, says it 's 22:00 meaning it's 10 p.m., so I must be behind 10 hours. This means that my longitude is 10hr times 15*/hr = 150* west of the prime meridian in Greenwich. My altitude is 75* south, meaning that my latitude is 75* south as well. Since I have a little map beside me, and since I have to sail to the nearest land, I should set sail northeast to Venezuela in South America. Thank you. |
#8
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"Zarkovic" wrote in news:y3Keb.2484$9l5.730@pd7tw2no:
Hi guys. Well first of all, I have to say that after years of thinking that I know one of the most common things, I just found out that I actually don't so that's why I am freaked out and require a check just to see if I am right for these basic astronomy questions. All this time I knew that the lines of longitude stretch from N to S and lines of latitude stretch from E to W. Then I just discovered that when latitude is measured, it's measured in a way that I thought that longitude was measured, meaning the measurement of altitude would be like 20* N and for longitude it would be like 64* E. It still doesn't make sense to me, why do you have these lines to go from N to S yet they measure coordinates in E and W. Anyhow here is my assignment, so can someone tell me if I am right or not. Thanks. Given resources: It's spring equinox, the Sun is on my meridian at 75* in the S, my UT clock says it 22:00 What is my longitude, latitude and where should I go in order to go to some land mass, instead of ice. 2. It's spring equinox meaning that the Sun's ecliptic will cross with the celestial equator on the celestial sphere. Since I have a watch, both my day and my night will last 12 hours each equally on this day, and today's date is most likely to be March 21. The Sun is on my meridian at altitude of 75* south, meaning that it's noon (12 p.m.) where I am standing at, and my latitude is 75* south. My watch, which is set to universal time, says it 's 22:00 meaning it's 10 p.m., so I must be behind 10 hours. This means that my longitude is 10hr times 15*/hr = 150* west of the prime meridian in Greenwich. My altitude is 75* south, meaning that my latitude is 75* south as well. Since I have a little map beside me, and since I have to sail to the nearest land, I should set sail northeast to Venezuela in South America. Thank you. Yes. You are 150W 75S. Head NW (to Chile as you say). Martin Lewicki |
#9
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"Zarkovic" wrote in news:y3Keb.2484$9l5.730@pd7tw2no:
Hi guys. Well first of all, I have to say that after years of thinking that I know one of the most common things, I just found out that I actually don't so that's why I am freaked out and require a check just to see if I am right for these basic astronomy questions. All this time I knew that the lines of longitude stretch from N to S and lines of latitude stretch from E to W. Then I just discovered that when latitude is measured, it's measured in a way that I thought that longitude was measured, meaning the measurement of altitude would be like 20* N and for longitude it would be like 64* E. It still doesn't make sense to me, why do you have these lines to go from N to S yet they measure coordinates in E and W. Anyhow here is my assignment, so can someone tell me if I am right or not. Thanks. Given resources: It's spring equinox, the Sun is on my meridian at 75* in the S, my UT clock says it 22:00 What is my longitude, latitude and where should I go in order to go to some land mass, instead of ice. 2. It's spring equinox meaning that the Sun's ecliptic will cross with the celestial equator on the celestial sphere. Since I have a watch, both my day and my night will last 12 hours each equally on this day, and today's date is most likely to be March 21. The Sun is on my meridian at altitude of 75* south, meaning that it's noon (12 p.m.) where I am standing at, and my latitude is 75* south. My watch, which is set to universal time, says it 's 22:00 meaning it's 10 p.m., so I must be behind 10 hours. This means that my longitude is 10hr times 15*/hr = 150* west of the prime meridian in Greenwich. My altitude is 75* south, meaning that my latitude is 75* south as well. Since I have a little map beside me, and since I have to sail to the nearest land, I should set sail northeast to Venezuela in South America. Thank you. Yes. You are 150W 75S. Head NW (to Chile as you say). Martin Lewicki |
#10
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Llanzlan Klazmon The 15th wrote:
Altitude is the angular measurement from your local horizon towards your local zenith. Azimuth is the compass bearing around your local horizon. Quibble: A compass bearing is measured from magnetic north, while azimuth is measured from geographic/celestial north, i.e. the point where the meridian crosses the horizon. A compass bearing must be corrected for "variation" (and also "deviation" caused by local magnetic fields) in order to derive the "true" bearing. -- Odysseus |
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