Astronomy Flashcards
Explain the pinhole method
When the sky is clear. Put a hole through a piece of paper. Position a second piece of paper behind and adjust the distance between them to bring the sun into focus.
Describe the appearance of the milky way with the naked eye.
A faint patch of light.
Why are time zones used on Earth?
Time zones are used to standardise sunrise and sunset hours for people living in locations which receive light from the sun at different times.
What are sundials used for?
Sundials are the earliest type of clock and use the Sun and its position to indicate the time of day, commonly known as solar time.
What is the equation for equation of time.
EOT = AST - MST
How will a meteor appear across the sky?
A split second as a bright streak of light probably from the tail of a comet burning in the atmosphere.
How many constellations are there in the sky?
88
What is a asterism?
Unofficial popular patters of bright stars in a constellation.
What coordinate system do we use to find constellations or stars.
Equatorial coordinate system in which equivalents of our latitude are declination and Right ascension.
Where is Right Ascension measured?
Eastwards from the first point in Aries.
What is a coordinate system that is more observer friendly than the equatorial system?
Horizontal system using azimuth and altitude.
How long is a sidereal day?
23 hours 56 minutes 4 seconds
What is the equation for hour angle?
Hour angle = local sidereal time - right ascension.
What does NCP stand for astronomy.
North celestial pole.
What is a circumpolar star?
A star that never sets below the horizon due to its proximity to the poles.
How are stars circumpolar?
The polar distance must be less than the altitude of the NCP.
What is the equation for a star to be circumpolar?
90 - declination < latitude of observer
How long does it usually takes the eyes to become dark adapted?
20 - 30 minutes.
What is used to find out solar time?
Shadow stick practical or sundial
Why is there not a lunar eclipse every month?
Due to the Moons 5.1 degree orbital tilt
How much is the moon tilt on its axis
1.5 degrees
When do high and low neap tides occur
When the Earth Sun Moon are aligned
What is a annular solar eclipse and how does it occur?
An annular solar eclipse is a special kind of partial solar eclipse in which the Moon is silhouettier disc. is smaller than other times.
It occurs due to the moon being close to the apogee in its elliptical orbit.
When is it a new moon?
When the suns rays hit the moon before earth
When is it a full moon?
When the sun hits the earth before the moon
How long is a sidereal day
23h 56m
What is the equation for EOT
EOT - AST - MST
Why is the lunar phase 2.2 days longer then the sydonic month?
Due to the time taken for the moon to complete a orbit around earth, the earth moon system had moved an angle of 27*
What is averted vision?
Looking slightly to the side of the object allowing light to fall onto the rods and the object to be seen.
What part of the eye helps with dark adapted vision?
The rods
If you go down the great square of pegasus what do you find?
Formalhaut.
If you go down the great square of Pegasus what do you find?
Formalhaut.
Explain how to do the shadow stick practical
- Set up your experiment so you will have an equal number of readings before noon
and after noon. - Place a long shadow stick in the ground. Note the,
(a) Clock time.
(b) Shadow length. - Take readings of the shadow length and clock time every 1 or 2 minutes to ensure
a good accuracy. Make sure all readings are equally spaced apart. - Plot your results in a table.
- The shortest shadow occurs at your local noon.
- Remember 4 minutes = 1◦ and your longitude is given by
Number of minutes after true (GMT)
Number of minutes after true (GMT) noon / 4
What is apparent solar time?
Apparent solar time is the time that is kept with reference to the sun’s position in
the sky
What is mean solar time
Mean solar time is the time kept with respect to the average length of a solar day,
which on average is 24 hours.
How many minutes for the earth to rotate one degree
1 degree = 4 minutes
Why is there annual variation in EOT?
The Earth’s elliptical orbit causes the sun to move slower or faster in the sky at different dates due to earths different speeds.
Tilt of the earth’s axis - close to the solstices the real sun is travelling faster from east to west than when close to the equinoxes.
The sun therefore lags behind and leaps ahead of the mean sun in its east - west motion
Where is inferior conjunction?
When the planet is between the Earth and the sun.
Where is superior conjunction?
Where the sun is between the planet and earth.
What is parralax angle?
The parallax angle is the angle between the Earth at one time of year, and the Earth six months later, as measured from a nearby star.
What is parralax angle?
The parallax angle is the angle between the Earth at one time of year, and the Earth six months later, as measured from a nearby star.
What is the equation that links distance and parralax angle?
What is the formula for parallax angle and distance?
d = 1/p
d = parsecs = 3.26 ly
p = arc seconds
How many arc seconds in 1 arc minute?
60 arc seconds
How many arc seconds in 1 arc minute?
60 arc seconds
What star is above the Plough when following the right side?
Polaris
Where do you follow on the GREAT SQUARE OF PEGASUS TO FIND ANDROMEDA?
Move diagonally toward the top left star of the Great square of pegasus.
When does a transit occur?
When a planet passes between a star and its observer.
