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If the fixed point is the intersection of the celestial equator and the hour circle that intersects the body's position on the celestial sphere, it is declination.
The only line that runs parallel through the equator is THE EQUATOR. [The Tropic of Cancer and the Tropic of Capricorn are parallel to the equator, but are north and south of it (respectively) at 23.5 degrees. So they do not run through the equator.] The lines of longitude all run through the equator, but they are not parallel to each other since they all meet up at both the North and South Poles.
The locus of all points of zero latitude ... sometimes also known as the "Equator" ... is the longest parallel of constant latitude. It's length is the equatorial circumference of the earth ... roughly 24,900 miles (40,073 km) .
A single line cannot be perpendicular or parallel. These are attributes of two (or more) lines.
Lines of latitude.
'Declination' of +30
Yes. "Declination" on the celestial coordinate system is the counterpart of "latitude" on the terrestrial coordinate system. Positive and negative declination correspond respectively to north and south latitude.
If the fixed point is the intersection of the celestial equator and the hour circle that intersects the body's position on the celestial sphere, it is declination.
Declination (positive and negative respectively) is the angular distance between north and south of the Celestial Equator.
You measure the angles from east from the first point of Aries (which is the place in the sky where the Sun crosses the celestial equator at the March equinox) and north from the ecliptic (declination).
Astronomers use the coordinate system of RA right ascension also called hour angle, and Declination (Dec)RA is the celestial equivalent of terrestrial longitude. Both RA and longitude measure an east-west angle along the equator; and both measure from a zero point on the equator. For longitude, the zero point is the Prime Meridian; for RA, the zero point is known as the First Point of Aries, which is the place in the sky where the Sun crosses the celestial equator at the March equinox. RA is always zero on the meridian of the celestial sphere which passes through the celestial poles and first point of Aries. Declination is comparable to latitude, projected onto the celestial sphere, and is measured in degrees north and south of thecelestial equator. Therefore, points north of the celestial equator have positive declinations, while those to the south have negative declinations. * An object on the celestial equator has a dec of 0°. * An object at the celestial north pole has a dec of +90°. * An object at the celestial south pole has a dec of −90°.
Declination is the angular measurement of a celestial body north or south of the "celestial equator". You can think of it as the equivalent of "celestial latitude". The "fixed stars" don't have any change in declination. (Well, they _DO_, but only very slightly and VERY slowly.) The Sun, Moon, and planets all have their own paths within the solar system, so their declinations will change on a day-to-day basis. The Sun is at a declination of zero precisely at the time of the equinox. In September, the Sun's declination is decreasing, and it goes negative immediately after the moment of the equinox. This is generally on September 21, but this can vary a day either way depending on the cycle of leap years.
Celestial Equator
Depends on the declination in question. There are 24 hours of right ascension in 360 degrees, so at the celestial equator (declination = 0 degrees) 1 hour of right ascension is equal to 15 degrees. But as you increase or decrease declination the right ascension lines converge to the celestial pole (like longitude lines on a globe). The angle covered by 1 hour of right ascension is therefore equal to (15 degrees x cos(declination) ), so at the celestial poles (declination = +/- 90 degrees) 1 hour of RA is 0 degrees.
This is true. The celestial equator ... the line of zero declination ... crosses the horizon due east and due west. However, the ecliptic ... the apparent path of the sun through the stars ... is inclined to the celestial equator, and can hit the horizon anywhere within 23.5 degrees north or south of the east-west directions, depending on the time of day and day of the year.
That's the point in the sky called the "Vernal Equinox" ... the point where the sun appears to cross the celestial equator on its way north, on March 21 each year.
Declination is.