Astronomical Observations

celestial sphere

imaginary sphere with infinite radius whose center is the earth and where all celestial bodies are contained

observer's horizon

great circle that is the intersection of observer's horizon and celestial sphere

observer's vertical

vertical that passes through observer's zenith and nadir, normal to the horizon

vertical circle

great circle passing through the observer's zenith and any celestial boxy, perpendicular to the horizon

celestial equator

great circle in the celestial sphere perpendicular to its axis of rotation

celestial axis

prolongation of earth's polar axis

hour circle

great circle passing through celestial poles and any celestial body, perpendicular to the celestial equator

observer's meridian

great circle passing through the zenith, nadir, and poles

east and west point

points of intersection of the prime vertical circle and the celestial horizon

celestial coordinate

used to define location or position of any celestial bodies by measuring angles based on 2 perpendicular reference planes that pass through the center of the celestial sphere

1. horizon system

2. right ascension equatorial system

3. hour angle system

4. ecliptic system

types of celestial coordinate systems

observer's horizon and vertical circle

except observer's meridian, great circles involved in the horizon system

azimuth, altitude, zenith distance

angles involved in the horizon system

azimuth

angle measured from the south to the star's horizontal position or the vertical center

altitude

angle measured from the horizon to the star

zenith distance

angle measured from the zenith to star

celestial equator and hour circle

except observer's meridian, great circles involved in the right ascension equatorial system

right ascension, declination, polar distance

angles involved in the right ascension equatorial system

right ascension

angle measured fromthe First Point of Aries to the star

declination

angle measured from the celestial equator to the star

polar distance

angle measured from North celestial pole to star

celestial equator and hour circle

except observer's meridian, great circles involved in the hour angle system

hour angle, declination, polar distance

angles involved in the hour angle system

upper branch

where the zenith is projected along the equator, looking from the north pole

hour angle

angle measured from the upper branch to the star

west, east

Earth rotates from to _

east, west

from the perspective of the Earth, the sun moves from ____ to ______

ecliptic

apparent motion of the Sun with respect to earth

obliquity

angle between the celestial equator and the ecliptic

23°27'-23°30'

range of obliquity

equinox

when ecliptic and celestial equator meets

solstice

when declination is the highest

21-Mar

vernal equinox date

23-Sep

autumnal equinox date

First Point of Aries

location of the vernal equinox in the celestial sphere

20-Jun

summer solstice date

21-Dec

winter solstice date

north polar distance

angle between ecliptic and north celestial pole; complementary of obliquity

+23°30'

obliquity at summer solstice

-23°30'

obliquity at winter solstice

ecliptic latitude

angle between ecliptic and the star, measured along the eliptic meridian

ecliptic longitude

angle from the vernal equinox to the star, measured along the ecliptic

ecliptic polar distance

angle between north celestial pole and star, measured along eliptic meridian

eastward

coming from the vernal equinox, how is the ecliptic longitude measured

equatorial stars

stars located along the equator

northern circumpolar stars

stars located along circles near the north poles

southern circumpolar stars

stars located along circles near the south poles

southern circumpolar stars

among the types of stars by position, which can't be seen by observer

rising or setting

when the star intersects the celestial horizon

prime vertical crossing

when the star intersects the prime vertical circle

culmination or transit

when the star intersects the celestial meridian

elongation

when the hour circle and vertical circle of the star are perpendicular to each other

wild T1 engineer's theodolite

instrument for astronomical observations

parallactic angle

angle between the vertical and hour circle of the str

tangency

observation of a star at its limbs instead of directly

Q1 and Q3; Q2 and Q4

at which quadrants should you observe star in direct? In reverse?

index error

when the initial vertical angle is not zero even if the telescope is set to be horizontally leveled

subtracted algebraically

how to apply index error correction

parallax

computations are based on the assumptions that all observations are done on the earth's center, even though they are done on its surface

added

how to apply parallax error

refraction

due to bending of light as it enters the atmosphere, causing the measurement to increase

subtracted

how to apply refraction error

hourly variation

distance of the sun from the north pole is only given at specific times when solar observation is best suited for azimuth determination, so variations per hour is added or subtracted to sun's given NPD value

north

in the PZS triangle, Az is measured from the

360-A; A

when measured in the morning, the azimuth of the sun with respect to A is ; in the afternoon?