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R.A direction?
Can someone enlighten me please?
I seem unable to find the answer to the following question. Where do you 'point' the R.A Drive when the Setting Circle is set to Zero? I have read it should point East to Aries and also due South. I know how to use the R.A but am stumped by the setting up. I have an EQ5 mount with a polar alignment scope. TIA Clear skies Martin A -- Remove star to reply |
#2
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Right Ascension corresponds to longitude on the Earth (east-west
measurement), with 0 hours R.A. being a _line_ that extends from the celestial poles through the point in Aries where the ecliptic crosses the equator. (It's like the 0° longitude line that was arbitrarily chosen to pass through Greenwich, England.) http://skyandtelescope.com/howto/bas...icle_562_1.asp When setting up an equatorially mounted telescope, the best procedure is to polar align it (get the scope's polar axis parallel to the Earth's), set the declination to +90 while the scope is still pointing toward Polaris, then point it at a bright star of known R.A. and Dec. and calibrate the other circle there. "Stargazer" wrote in message ... Can someone enlighten me please? I seem unable to find the answer to the following question. Where do you 'point' the R.A Drive when the Setting Circle is set to Zero? I have read it should point East to Aries and also due South. I know how to use the R.A but am stumped by the setting up. I have an EQ5 mount with a polar alignment scope. TIA Clear skies Martin A -- Remove star to reply |
#3
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Right Ascension corresponds to longitude on the Earth (east-west
measurement), with 0 hours R.A. being a _line_ that extends from the celestial poles through the point in Aries where the ecliptic crosses the equator. (It's like the 0° longitude line that was arbitrarily chosen to pass through Greenwich, England.) http://skyandtelescope.com/howto/bas...icle_562_1.asp When setting up an equatorially mounted telescope, the best procedure is to polar align it (get the scope's polar axis parallel to the Earth's), set the declination to +90 while the scope is still pointing toward Polaris, then point it at a bright star of known R.A. and Dec. and calibrate the other circle there. "Stargazer" wrote in message ... Can someone enlighten me please? I seem unable to find the answer to the following question. Where do you 'point' the R.A Drive when the Setting Circle is set to Zero? I have read it should point East to Aries and also due South. I know how to use the R.A but am stumped by the setting up. I have an EQ5 mount with a polar alignment scope. TIA Clear skies Martin A -- Remove star to reply |
#4
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Correction: the ecliptic crosses the celestial equator in Pisces now
instead of Aries, due to precession. So that's really the starting point for R.A. "Bill Nunnelee" wrote in message hlink.net... Right Ascension corresponds to longitude on the Earth (east-west measurement), with 0 hours R.A. being a _line_ that extends from the celestial poles through the point in Aries where the ecliptic crosses the equator. (It's like the 0° longitude line that was arbitrarily chosen to pass through Greenwich, England.) http://skyandtelescope.com/howto/bas...icle_562_1.asp When setting up an equatorially mounted telescope, the best procedure is to polar align it (get the scope's polar axis parallel to the Earth's), set the declination to +90 while the scope is still pointing toward Polaris, then point it at a bright star of known R.A. and Dec. and calibrate the other circle there. "Stargazer" wrote in message ... Can someone enlighten me please? I seem unable to find the answer to the following question. Where do you 'point' the R.A Drive when the Setting Circle is set to Zero? I have read it should point East to Aries and also due South. I know how to use the R.A but am stumped by the setting up. I have an EQ5 mount with a polar alignment scope. TIA Clear skies Martin A -- Remove star to reply |
#5
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Correction: the ecliptic crosses the celestial equator in Pisces now
instead of Aries, due to precession. So that's really the starting point for R.A. "Bill Nunnelee" wrote in message hlink.net... Right Ascension corresponds to longitude on the Earth (east-west measurement), with 0 hours R.A. being a _line_ that extends from the celestial poles through the point in Aries where the ecliptic crosses the equator. (It's like the 0° longitude line that was arbitrarily chosen to pass through Greenwich, England.) http://skyandtelescope.com/howto/bas...icle_562_1.asp When setting up an equatorially mounted telescope, the best procedure is to polar align it (get the scope's polar axis parallel to the Earth's), set the declination to +90 while the scope is still pointing toward Polaris, then point it at a bright star of known R.A. and Dec. and calibrate the other circle there. "Stargazer" wrote in message ... Can someone enlighten me please? I seem unable to find the answer to the following question. Where do you 'point' the R.A Drive when the Setting Circle is set to Zero? I have read it should point East to Aries and also due South. I know how to use the R.A but am stumped by the setting up. I have an EQ5 mount with a polar alignment scope. TIA Clear skies Martin A -- Remove star to reply |
#6
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Thanks Bill
Now i understand a lot more. Funny how you spend ages wondering about something and then WHAM!! the understanding sinks in :-) Clear skies Martin A "Bill Nunnelee" wrote in message hlink.net... Correction: the ecliptic crosses the celestial equator in Pisces now instead of Aries, due to precession. So that's really the starting point for R.A. "Bill Nunnelee" wrote in message hlink.net... Right Ascension corresponds to longitude on the Earth (east-west measurement), with 0 hours R.A. being a _line_ that extends from the celestial poles through the point in Aries where the ecliptic crosses the equator. (It's like the 0° longitude line that was arbitrarily chosen to pass through Greenwich, England.) http://skyandtelescope.com/howto/bas...icle_562_1.asp When setting up an equatorially mounted telescope, the best procedure is to polar align it (get the scope's polar axis parallel to the Earth's), set the declination to +90 while the scope is still pointing toward Polaris, then point it at a bright star of known R.A. and Dec. and calibrate the other circle there. "Stargazer" wrote in message ... Can someone enlighten me please? I seem unable to find the answer to the following question. Where do you 'point' the R.A Drive when the Setting Circle is set to Zero? I have read it should point East to Aries and also due South. I know how to use the R.A but am stumped by the setting up. I have an EQ5 mount with a polar alignment scope. TIA Clear skies Martin A -- Remove star to reply |
#7
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Thanks Bill
Now i understand a lot more. Funny how you spend ages wondering about something and then WHAM!! the understanding sinks in :-) Clear skies Martin A "Bill Nunnelee" wrote in message hlink.net... Correction: the ecliptic crosses the celestial equator in Pisces now instead of Aries, due to precession. So that's really the starting point for R.A. "Bill Nunnelee" wrote in message hlink.net... Right Ascension corresponds to longitude on the Earth (east-west measurement), with 0 hours R.A. being a _line_ that extends from the celestial poles through the point in Aries where the ecliptic crosses the equator. (It's like the 0° longitude line that was arbitrarily chosen to pass through Greenwich, England.) http://skyandtelescope.com/howto/bas...icle_562_1.asp When setting up an equatorially mounted telescope, the best procedure is to polar align it (get the scope's polar axis parallel to the Earth's), set the declination to +90 while the scope is still pointing toward Polaris, then point it at a bright star of known R.A. and Dec. and calibrate the other circle there. "Stargazer" wrote in message ... Can someone enlighten me please? I seem unable to find the answer to the following question. Where do you 'point' the R.A Drive when the Setting Circle is set to Zero? I have read it should point East to Aries and also due South. I know how to use the R.A but am stumped by the setting up. I have an EQ5 mount with a polar alignment scope. TIA Clear skies Martin A -- Remove star to reply |
#8
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Bill Nunnelee wrote:
Correction: the ecliptic crosses the celestial equator in Pisces now instead of Aries, due to precession. So that's really the starting point for R.A. The vernal equinox is often called the "first point of Aries", though, also marking the starting point for the "tropical zodiac" and serving as the reference for positions in "ecliptic longitude". -- Odysseus |
#9
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Bill Nunnelee wrote:
Correction: the ecliptic crosses the celestial equator in Pisces now instead of Aries, due to precession. So that's really the starting point for R.A. The vernal equinox is often called the "first point of Aries", though, also marking the starting point for the "tropical zodiac" and serving as the reference for positions in "ecliptic longitude". -- Odysseus |
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