Navigating the Night Sky Checklist. Observe Educate Have Fun

Transcription

1 Navigating the Night Sky Checklist Observe Educate Have Fun TAAS General Meeting April 4, 2015

2 Introduction I have been observing the night sky for many years. I am still learning what works best for me. I am going to share with you some basic techniques that have helped me learn to Navigate the Night Sky I do not have all the answers But there are many answers sitting around you here in the TAAS family.

3 My first real star book in 1958 at age 14

4 3 months later $$ = telescope

5 For 40 years I flew airplanes For 40 years I used a checklist. Now I have created a checklist To help me Navigate the Night Sky

6 Navigating the Night Sky Checklist 9 Procedures (P) P# 1. Before Observing P# 2. Establishing Sky Awareness As I take you through the checklist, I will add some Sky Lessons Sky Lesson 1 imaginary sky markers P# 3. Orient the Sky Map to the Night Sky P# 4. Visually Locating the Major Constellations P# 7. Locating Objects With Pointing Devices Sky Lesson 6 Types of pointing devices P# 5. Locating Objects With the naked Eye Sky Lesson 2 motion in the sky Sky Lesson 3 Angles in the sky P# 8. Locating Objects by Star Hopping Sky Lesson 7 How to star hop P# 9. Button Pushing Sky Lesson 4 Magnitude (brightness) P# 6. Locating Objects With Binoculars Sky Lesson 5 FOV and Geometric Method

7 P# 1. Before Observing Checklist 1. Select as dark a location as feasible. 2. Gather observing materials a. Sky Map, planisphere b. Red light flashlight c. Observing chair d. Observing equipment (naked eye, binoculars, telescope) 3. Dress appropriately for the weather

8 P# 2. Establishing Sky Awareness (establish your bearings). 1. Determine the direction NORTH. 2. Determine the other cardinal directions. 3. Locate the zenith 4. Locate the meridian 5. Approximate the celestial equator 6. Approximate the ecliptic (where the planets are)

9 Sky Lesson 1.0 Sky Lesson 1 Imaginary Sky Markers 1. What is the celestial sphere? 2. What are the celestial poles? These are markers 3. What is the celestial equator? 4. What is the ecliptic? that we place on the celestial sphere to help us get our bearings. 5. What is the Zenith? 6. What is the Meridian?

10 Sky Lesson 1.1 What is the celestial sphere? To help us navigate the night sky, we will place imaginary markers on this sphere It is the inside surface of an imaginary sphere that surrounds the earth on which we observe all the objects in the night sky Even though the stars are all at different distances from the earth, they all appear beside each other on the celestial sphere

11 Sky Lesson 1.2 The Imaginary Markers Celestial poles are a projection of the north and south poles on the sphere. Celestial equator is a projection of the equator onto the sphere. Ecliptic is where on the sphere we will see the sun and the planets throughout the year.

12 Sky Lesson 1.3 When an object is on the meridian, We say that it is transiting. It will be due south of your position. The Imaginary Markers (cont.) This will be the highest the object will ever get in the night sky. For objects that are far south this is the best time to observe them. The zenith is the point directly overhead on the sphere. The meridian is a line from the northern horizon through the zenith to the southern horizon.

13 P# 2. Establishing Sky Awareness (establish your bearings) (cont.). 1. Determine the direction NORTH. 2. Determine the other cardinal directions. We now know what these markers below are, but how do we find North? 3. Locate the zenith 4. Locate the meridian 5. Approximate the celestial equator 6. Approximate the ecliptic (where the planets are)

14 P# 2. Establishing Sky Awareness (establish your bearings)(cont.) 1. Determine the direction NORTH. Find the North Star Two stars of the bowl always point to Polaris (north)

15 Cassiopeia and the Big Dipper another stellar relationship to find North Cassiopeia is always opposite to the Big Dipper

16 A way to find south Westerly Easterly Orion s sword Points South South Most accurate In January at 10 pm

17 At other times and dates, the situation is different A little less accurate during other months at 10 pm Easterly Westerly Easterly Westerly December Orion is so prominently visible in the night sky that the relationship is still useful. March

18 Orion s belt is a good marker for the celestial equator

19 What are the Cardinal Headings? A compass rose showing the four cardinal directions, the four ordinal directions, plus eight further divisions.

20 Why is this important to know the Cardinal Directions? On the Sky Map, notice that east and west are backward from a road map When you hold the map above your head to look at the night sky, the directions are correct The Sky Map we will use will use cardinal headings to orient your viewing of the night sky.

21 Why is this important to know the Cardinal Directions? (cont.) The Sky Wheel we will use will use cardinal headings to orient your viewing of the night sky.

22 This completes Checklist P# 2 P# 2. Establishing Sky Awareness (establish your bearings). 1. Determine the direction NORTH. 2. Determine the other cardinal directions. 3. Locate the zenith 4. Locate the meridian 5. Approximate the celestial equator 6. Approximate the ecliptic (where the planets are)

23 P# 3. Orient the Sky Map to the Night Sky 1. Locate the cardinal headings on your star map. 2. Face the direction you wish to view the sky. 3. Place the direction that you are viewing at the bottom of your star map. 4. Hold the star map on front of you and look from the sky map to the sky. 5. Look from the sky to the sky map.

24 P# 3. Orient the Sky Map to the Night Sky (cont.) Viewing to the south We will first look to the SOUTH. Make sure that SOUTH is at the bottom of the chart. Note, that the words are readable and not up-side down. Sirius, is easy to read.

25 P# 3. Orient the Sky Map to the Night Sky (cont.) Viewing to the north Make sure that NORTH is at the bottom of the chart. Note, that the words are readable and not up-side down. POLARIS is easy to read.

26 P# 3. Orient the Planisphere to the Night Sky (cont.) Viewing to the north Make sure that NORTH is at the bottom of the planisphere. Note, that the words are readable and not up-side down. POLARIS is easy to read.

27 This completes Checklist P# 3 P# 3. Orient the Sky Map to the Night Sky 1. Locate the cardinal headings on your star map. 2. Face the direction you wish to view the sky. 3. Place the direction that you are viewing at the bottom of your star map. He will probably buy a telescope with buttons. 4. Hold the star map in front of you and look from the sky map to the sky. 5. Look from the sky to the sky map.

28 P# 4. Visually Locate the Major Constellations 1. Select a constellation from TAAS Fab 50 seasonal list. (see for the list). Winter Orion 2. Locate the constellation on your star map. 3. Place the direction that you need to view to see the constellation at the bottom of the chart. 4. Hold the star map in front of you and look from the sky map to the sky to locate the constellation. Spring Leo 5. Look from the sky to the sky map to confirm you are viewing the correct constellation. Summer Scorpius I like to begin my constellation viewing as it gets dark. The brighter stars become visible first and it is easier to locate the major constellations Fall Cassiopeia

29 P# 4. Visually Locate the Major Constellations (cont.) Locating Ursa Major and the Big Dipper View map to the - sky View sky to the - map

30 P# 4. Visually Locate the Major Constellations (cont.) When I begin my viewing sessions 1. I take several minutes to view the entire sky. 2. I locate the major constellations. 3. I constantly reference my big view sky maps to stay oriented (keep my bearings). 4. Whenever I gest lost, I go back to a major constellation and re-establish my bearings. 5. The more I do this, the better I learn the sky. I like to begin my constellation viewing as it gets dark. The brighter stars become visible first and it is easier to locate the major constellations

31 This completes Checklist P# 4 P# 4. Visually Locate the Major Constellations 1. Select a constellation from TAAS Fab 50 seasonal list. (see for the list). Winter Orion 2. Locate the constellation on your star map. 3. Place the direction that you need to view to see the constellation at the bottom of the chart. 4. Hold the star map on front of you and look from the sky map to the sky to locate the constellation. Spring Leo 5. Look from the sky to the sky map to confirm you are viewing the correct constellation. Summer Scorpius Fall Cassiopeia

32 Transitioning from awareness to finding The first 4 procedures helped get our bearings to the night sky. Now we will look at procedures on how to find things in the sky.

33 What are we looking for in the night sky? Object Naked eye Binocular Telescope Few Many All Moon X X X Planets X X X Globular Clusters X X Open Clusters X X X Galaxies X X X Nebulas X X X

34 P# 5. Locating Objects With the Naked Eye 1. Reference a sky map, chart or other lists to identify the objects that are visible to the naked eye. A very good source is the monthly Sky Map available on the TAAS Fab 50 website. ( 2. Identify the constellation that the naked eye object is in. 3. Using your sky map or planisphere, locate the constellation in the night sky. 4. Identify a bright star(s) in the constellation that is near the naked eye object. 5. Reference your sky map to determine a distance and direction from the bright star to find the naked eye object. 6. If the naked eye object is not in a major constellation, create a path to the object using two or more bright stars.

35 Sky Lesson 2.0 Sky Lesson 2 Motion in the Night Sky 1. Objects in the night sky do not stay in one place. 2. During the night they move across the night sky. 3. As observers, we have to keep up with their motion if we wish to observe them for any length of time. 4. We will consider two different motion: a. daily motion b. yearly motion

36 Sky Lesson 2.1 Apparent Daily Motions of the Night sky Apparent motion right to - left Looking north Apparent motion left to - right Looking south To us the sky appears to rotate east to west It is the earth that actually rotates west to east

37 Sky Lesson 2.2 How far does a star move in 1 hour? 15 0 per hour The Earth rotates every 24 hours, 360 degrees in 24 hours is 360/24 = 15 degrees per hour, or 15/60 = 0.25 degrees per minute.

38 Sky Lesson 2.3 How far does a star move in 1 hour? (cont.) Looking North motion counterclockwise Looking South motion clockwise

39 Sky Lesson 2.4 Yearly Motion Different times of the year different constellations are visible

40 Sky Lesson 2.5 Yearly Motion (cont.) Feb May Aug Nov

41 P# 5. Locating Objects With the Naked Eye (cont.) 1. Reference a sky map, chart or other lists to identify the objects that are visible to the naked eye. A very good source is the monthly Sky Map available on the TAAS Fab 50 website. (

42 P# 5. Locating Objects With the Naked Eye (cont.) We will try to locate M 44 the Beehive

43 P# 5. Locating Objects With the Naked Eye (cont.) 2. Identify the constellation that the naked eye object is in. 3. Using your sky map or planisphere, locate the constellation in the night sky. Cancer The stars in Cancer are very dim

44 P# 5. Locating Objects With the Naked Eye (cont.) The stars in Cancer are very dim 4. Identify a bright star(s) in the constellation that is near the naked eye object. 5. Reference your sky map to determine a distance and direction from the bright star to find the naked eye object. This year we have Jupiter very close, so we can use it as the bright star. We look just to the right of Jupiter to find M 44

45 P# 5. Locating Objects With the Naked Eye (cont.) 6. If the naked eye object is not in a major constellation, create a path to the object using two or more bright stars. Regulus Pollux About half way between and slightly to the right

46 Sky Lesson 3.0 Sky Lesson 3 Angles in the Sky When we observe objects in the night sky (on the inside of the celestial sphere), we use angles to measure the distance between the objects.

47 Sky Lesson 3.1 We use angles to measure the distance across the night sky We subdivide each degree into 60 arcminutes and each arcminute into 60 arcseconds. (The figure is not drawn to scale.)

48 Sky Lesson 3.2 We use angles to measure the distance across the night sky (cont.) 30 0

49 Sky Lesson 3.3 We use angles to measure the distance across the night sky (cont.)

50 Sky Lesson 3.4 Locating Polaris our latitude is 35 0 N Polaris altitude is 35 0

51 Sky Lesson 4.0 Sky Lesson 4 Magnitude (brightness) When we observe objects in the night sky We very quickly observe that not all objects are of the Same brightness.

52 Sky Lesson 4.1 Magnitude (brightness)

53 Sky Lesson 4.3 Magnitude (brightness) (cont.) The size of the dot represents the brightness of the star

54 This completes Checklist P# 5 P# 5. Locating Objects With the Naked Eye 1. Reference a sky map, chart or other lists to identify the objects that are visible to the naked eye. A very good source is the monthly Sky Map available on the TAAS Fab 50 website. ( 2. Identify the constellation that the naked eye object is in. 3. Using your sky map or planisphere, locate the constellation in the night sky. 4. Identify a bright star(s) in the constellation that is near the naked eye object. 5. Reference your sky map to determine a distance and direction from the bright star to find the naked eye object. 6. If the naked eye object is not in a major constellation, create a path to the object using two or more bright stars.

55 Understanding the use of measured angles in the night sky gives us a feel for distance across the sky.

56 We use angles to measure the distance across the night sky

57 Red lines mark official borders of several constellations near Orion. Yellow lines connect recognizable patterns of stars within constellations. Sirius, Procyon, and Betelgeuse form a pattern that spans several constellations and is called the Winter Triangle. It is easy to find on clear winter evenings. Stars appear to lie on a great celestial sphere that surrounds the Earth.

58 From any place on Earth, the local sky looks like a dome (hemisphere). This diagram shows key reference points in the local sky. It also shows how we can describe any position in the local sky by its altitude and direction. We subdivide each degree into 60 arcminutes and each arcminute into 60 arcseconds. (The figure is not drawn to scale.)

59 This diagram shows why the Sun appears to move steadily eastward along the ecliptic, through the constellations of the zodiac. As Earth orbits the Sun, we see the Sun against the background of different zodiac constellations at different times of year. For example, on August 21 the Sun appears to be in Leo, because it is between us and the much more distant stars that make up Leo.

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61 This diagram shows the Sun s path on the solstices and equinoxes for the Northern Hemisphere sky (latitude 40 N). Notice that the Sun rises exactly due east and sets exactly due west only on the equinoxes. The summer solstice occurs on the day that the Sun rises and sets farthest to the north and reaches its highest point in the sky. The winter solstice occurs on the day that the Sun rises and sets farthest to the south and traces its lowest path through the sky.

62 What is the Zenith? The point in the sky directly above an observer.

63 What is the Meridian? The arc that goes through the north point on the horizon, the zenith, and south point on the horizon is called the meridian

64 In the Southern Hemisphere, there is no easily visible South Star

65 Sky Lesson Two 1. Daily motion of the sky 2. Annual motion of the sky

66 The Zodiac is defined by 13 constellations that lie along the annual path of the sun across the sky.

67 How far does a star move in 1 hour? The Earth rotates every 24 hours, 360 degrees in 24 hours is 360/24 = 15 degrees per hour, or 15/60 = 0.25 degrees per minute.

68 Daily movement of the moon The Moon orbits the Earth every 27.3 days. 360 degrees / 27.3 days = 13 degrees per day. the moon will appear to have moved 13 degrees in the sky from one day to the next.

69 Five basic steps 1. Situational awareness 2. Basic motions of the night sky 3. Angular measurements 4. Basic object locating 5. Using the celestial coordinate system

70 Objectives 1. As an observer understand the basics of navigating the night sky. 2. Gain confidence as an observer to use your equipment (maps, binoculars, telescopes). 3. Become an experienced observer and participate in observing exercises a. TAAS observing events (GNTO Messier Marathon) b. Astronomical League observing programs). c. Star party programs (Okie-Tex, TSP, etc.)

71 Situational Awareness This means that you know: 1. the Cardinal Headings. 2. the Meridian 3. the Zenith In other words, you know your directions well enough to be able to use a basic sky map which is the first fundamental step to being able to navigate the night sky.

72 Motions in the Night Sky Two motions are apparent over time as we view the night sky 1. Daily (diurnal) motion 2. Annual motion Diurnal motion is the daily motion of stars and other celestial bodies across the sky. This motion is due to the Earth's rotation from west to east, which causes celestial bodies to have an apparent motion from east to west.

73 Motions in the Night Sky Two motions are apparent over time as we view the night sky 1. Daily (diurnal) motion 2. Annual motion Diurnal motion is the daily motion of stars and other celestial bodies across the sky. This motion is due to the Earth's rotation from west to east, which causes celestial bodies to have an apparent motion from east to west.

74 As Earth orbits the sun, the sun appears to drift across the background stars. The ecliptic marks out the path of this motion on the sky. Credit: Wikipedia The ecliptic marks the path of the sun. It s the projection of Earth s orbit onto the sky. And it s an essential part of any stargazer s vocabulary.

75 The planets Mercury, Venus, Mars, and Saturn lined up along the ecliptic (red line) shortly after sunset. Credit: Jia Hao (via Wikipedia)

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81 cardinal headings

82 meridian cardinal headings

83 meridian cardinal headings

84 meridian zenith

85 meridian zenith

86 Aviation in itself is not inherently dangerous. But to an even greater degree than the sea, it is terribly unforgiving of any carelessness, incapacity or neglect.

87 A way to find north The pointer stars of the BIG DIPPER point to the north star

88 Apparent Motion east of the Night sky south north west

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90 Movement in One Night Since the Earth rotates every 24 hours, any given star must move completely around the sky in 24 hours. A complete circle around the sky is 360 degrees. 360 degrees in 24 hours is 360/24 = 15 degrees per hour, or 15/60 = 0.25 degrees per minute. You can do a lot with those figures. Some examples: 1. The angular diameter of the Moon is about 0.5 degrees. This means that a star will travel a distance in the sky equivalent to the apparent width of the moon in about 2 minutes. (Stars don't "overtake and pass" the moon, since the moon is moving too. You need to compare to a stationary object like a chimney to see this motion.) 2. Suppose Jupiter has just risen, but it's so close to the horizon that you can't easily observe it yet. When will it be higher? Suppose we'd like to wait till it travels about 45 degrees across the sky. That will take about 45 / 15 = 3 hours. 3. A typical amateur telescope with a typical eyepiece (say, a 200 mm Dobsonian reflector with a 20mm Plossl eyepiece) shows you a piece of sky about 1 degree wide. So, stars will drift completely through this field of view in about 4 minutes. Or, if you centre a star, it will drift out of your field of view in about 2 minutes. 4. Observing planets is worse. We like to use high power, with a narrower field of view. That same telescope, set up for 200x magnification, only shows about 1/2 degree of sky, so Saturn or Jupiter will drift out of your field of view in about a minute. This is why owners of non-motorized telescopes appreciate the wider-field eyepieces like Naglers or Radians, to keep objects in their field of view longer.

91 Movement Between Nights The Earth orbits the Sun once every days. So, at some fixed time of night (say, midnight) any given star will be in a given position one day, slightly moved from that position the next day, and so on, returning to the same position days later. So, at the same time of night, a star moves its apparent position 360 / = 0.99 degrees each day. Let's call it 1 degree. So if a star - say, Sirius - is just at the horizon at 9:00 PM on a given day, it will be about 30 degrees higher at 9:00 PM about 30 days later. If the Big Dipper is sitting flat in the sky at midnight on a given day (i.e. horizontal and able to hold water), at midnight 180 days later it will be upside down, on the other side of the North Star.

92 The Moon The Moon orbits the Earth every 27.3 days. 360 degrees / 27.3 days = approximately 13 degrees per day. So at any given time of night, the moon will appear to have moved 13 degrees in the sky from one day to the next.

93 The bowl of the Big Dipper is about 10 wide and 5 deep. The entire handle is 16 long, and the whole Dipper is 26 long. Angle estimates using fist and fingers, with arm outstretched. The angle between two points in the sky is defined as the angle between two imaginary lines running from you out to those points. For the two stars shown, the angle is about 16 degrees.

94 2. Establishing Awareness (establish your bearings). How to find the North Star Two stars of the bowl always point to Polaris (north)

95 Navigating the Night Sky Checklist 9 Procedures (P) P# 1. Before Observing P# 2. Establishing Sky Awareness Sky Lesson 1 imaginary sky markers P# 3. Orient the Sky Map to the Night Sky Sky Lesson 2 motion in the sky P# 4. Visually Locating the Major Constellations Sky Lesson 3 Angles in the sky P# 5. Locating Objects With the naked Eye Sky Lesson 4 Magnitude (brightness) P# 7. Locating Objects With Pointing Devices Sky Lesson 6 Types of pointing devices P# 8. Locating Objects by Star Hopping Sky Lesson 7 How to star hop P# 9. Button Pushing P# 6. Locating Objects With Binoculars Sky Lesson 5 FOV and Geometric Method