Topic 6 (Celestial Observations)

Question 1

What constellations do you need to recognise

Answer 1

Cassiopeia 
Cygnus 
Orion
Plough
Southern cross
Summer Triangle 
Square of Pegasus
(Look at constellations poster for diagrams)

Question 2

What is a constellation

Answer 2

A section of the sky with stars bearing no resemblance to their name

Question 3

What is an asterism

Answer 3

An asterism is an UNOFFICIAL set of stars that do bear close likeness to there name such as Orión’s belt

Question 4

What do planets slowly move across night after night

Answer 4

The zodiacal band

Question 5

What are the northern and southern lights at the poles called

Answer 5

Aurora borealis and aurora australis

Question 6

What does a supernova look like to the naked eye

Answer 6

A sudden appearance of a bright star that very slowly fades

Question 7

Comets are rare and appear as an…

Answer 7

Extended fuzzy object with one or two tails

Question 8

What do many asterisms contain

Answer 8

Pointers that lead to a specific object in the sky such as the Big Dipper and Polaris

Question 9

What is the celestial sphere

Answer 9

An imaginary sphere concentric its earth that acts as a similar system as latitude and longitude on earth but for space

Question 10

What is the ecliptic on the celestial sphere

Answer 10

A line around the earth that maps the suns path over a year

Question 11

What is the first point of Aries on the celestial sphere

Answer 11

where the ecliptic cuts across the celestial equator as it moves from south to north

Question 12

What is the equatorial co-ordinate system

Answer 12

A co-ordinate system for space in which latitude and longitude are replaced by declination and right ascension

Question 13

What is declination

Answer 13

Declination is the projection of latitude onto the celestial sphere
(- and + are equal to south and north)

Question 14

What is right ascension

Answer 14

Right ascension is measured eastwards form the first point of Aries it’s is measured in hours where and hour = 15 degrees

Question 15

What is the horizontal co-ordinate system

Answer 15

A more user friendly co-ordinate system using azimuth and Altitude instead of latitude and longitude

Question 16

What is azimuth

Answer 16

A simple bearing measured in degrees from due north (geographical) moving round eastwards to the point on the observers horizon directly under the star ,it ranges from 0 to 360 degrees

Question 17

What is altitude

Answer 17

Found by the angle from the observers horizon upwards to the star or other celestial object; it ranges from 0 to 90 degrees( the observers zenith)

Question 18

What is a sidereal day

Answer 18

How long it takes the earth to rotate 360degrees which takes (23hrs 56mins)

Question 19

What is a solar day

Answer 19

A solar day is a sidereal day + another 4 mins for the earth to align a given point on the surface with the sun.therefore It follows that the stars rise reach their highest point and set 4 minutes earlier each day

Question 20

What is local sidereal time

Answer 20

Local sidereal time is the right ascension of a star on the observers meridian - remember right ascension is measured in hours

Question 21

Observers often use hour angle what is it

Answer 21

Hour angle is the time in hours and mins since the object was last crossing over the meridian
If hour angle is negative it tells how much time before the star or other celestial object will cross their meridian

Question 22

What is polar distance

Answer 22

Polar distance is a useful measure of the angular distance of a celestial object from the NCP since the declination of the NCP is +90 it follows that
Polar distance =90degrees - declination

Question 23

What is a circumpolar star

Answer 23

When a stars polar distance is so small it remains visible all the time

Question 24

What makes a star circumpolar

Answer 24

For a star to be circumpolar, it’s polar distance must be less than the altitude of NCP(equal to the observers latitude)

Question 25

For a star to be circumpolar equation

Answer 25

90degrees - declination < latitude of the observer

Question 26

Example (circumpolar equation)

Answer 26

Thunan (dec=+64degrees) is circumpolar from ulaanbaatar (lat 48degrees) because 90-64=26<48

Question 27

When is the best time to observe a celestial objects with the naked eye

Answer 27

When it approaches culmination (their highest point)

Question 28

What must the eye be before any naked eye observing can be done

Answer 28

Dark adapted (this takes about 20-30mims of darkness)

Question 29

How should you look at faint objects such as the andromeda galaxy

Answer 29

Use averted vision (looking slightly to the side of it) as it is necessary to stimulate the rods to see this and not the cones

Question 30

What factors affect naked eye observing

Answer 30

.light pollution
.landscape
.cloud
.transparency(recent rain removes dust)
Steadiness of the atmosphere (measured from I-V on the Antoniadi scale)

Question 31

What are the prominent stars of Cygnus the swan

Answer 31

Deneb, top right

Question 32

What are the significant stars of Cassiopeia

Answer 32

Schedar

Question 33

What are the significant stars of the southern cross

Answer 33

Mimosa, left

Acrux, bottom

Question 34

What are the significant stars in the Summer Triangle asterism

Answer 34

Deneb, top left
Vega, top right
Altair, bottom

Question 35

What stars con be found from pointers in the Big Dipper

Answer 35

Arcturus, follow the handle

Polaris, follow the line from the two end stars upwards

Question 36

What stars can be found from following the Great square of pegasus

Answer 36

Fomalhaut, follow the right two stars down