Navigating the Night Sky Checklist · Navigating the Night Sky Checklist 9 Procedures (P) P# 1....

transcript

Navigating the Night Sky Checklist

TAAS General Meeting April 4, 2015

Observe Educate Have Fun

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.

My first “real star” book in 1958 at age 14

$$ = telescope

3 months later

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

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 P# 4. Visually Locating the Major Constellations P# 5. Locating Objects With the naked Eye Sky Lesson 2 – motion in the sky

Sky Lesson 3 – Angles in the sky

Sky Lesson 4 – Magnitude (brightness)

P# 6. Locating Objects With Binoculars Sky Lesson 5 – FOV and Geometric Method

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

As I take you through the checklist, I will add some “Sky Lessons”

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

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)

P# 2. Establishing Sky Awareness (establish your bearings).

Sky Lesson 1 Imaginary Sky Markers

1. What is the celestial sphere? 2. What are the celestial poles? 3. What is the celestial equator? 4. What is the ecliptic? 5. What is the Zenith? 6. What is the Meridian?

These are “markers” that we place on the celestial sphere to help us get our bearings.

Sky Lesson 1.0

What is the celestial 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

To help us navigate the night sky, we will “place” imaginary markers on this sphere

Sky Lesson 1.1

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.

Sky Lesson 1.2

The Imaginary Markers (cont.)

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.

When an object is on the meridian, We say that it is transiting. It will be “due south” of your position.

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.

Sky Lesson 1.3

P# 2. Establishing Sky Awareness (establish your bearings) (cont.).

We now know what these markers below are, but how do we find North?

1. Determine the direction NORTH.

P# 2. Establishing Sky Awareness (establish your bearings)(cont.)

Find the North Star

Two stars of the bowl always point to Polaris (north)

Cassiopeia and the Big Dipper another stellar relationship to find North

Cassiopeia is always opposite to the Big Dipper

A way to find south

Westerly

Easterly

Orion’s sword Points South

Most accurate In January at 10 pm

A little less accurate during other months at 10 pm

Easterly Easterly

Westerly Westerly

December March

Orion is so prominently visible in the night sky that the relationship is still useful.

At other times and dates, the situation is different

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

What are the Cardinal Headings?

A compass rose showing the four cardinal directions, the four ordinal directions, plus eight further divisions.

Why is this important to know the Cardinal Directions?

The Sky Map we will use will use cardinal headings to orient your viewing of the night sky.

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 Wheel we will use will use cardinal headings to orient your viewing of the night sky.

Why is this important to know the Cardinal Directions? (cont.)

P# 2. Establishing Sky Awareness (establish your bearings).

This completes Checklist P# 2

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.

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.

P# 3. Orient the Sky Map to the Night Sky (cont.)

Viewing to the south

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.

P# 3. Orient the Sky Map to the Night Sky (cont.)

Viewing to the north

P# 3. Orient the Planisphere to the Night Sky (cont.)

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.

Viewing to the north

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 in front of you and look from the sky map to the sky. 5. Look from the sky to the sky map.

P# 3. Orient the Sky Map to the Night Sky

He will probably buy a telescope with “buttons.”

P# 4. Visually Locate the Major Constellations

1. Select a constellation from TAAS Fab 50 seasonal list. (see www.TAAS.org for the list). 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. 5. Look from the sky to the sky map to confirm you are viewing the correct constellation.

Fall Cassiopeia

Summer Scorpius

Spring Leo

Winter Orion

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

P# 4. Visually Locate the Major Constellations (cont.)

View map – to – the - sky

View sky – to – the - map

Locating Ursa Major and the ‘Big Dipper”

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

P# 4. Visually Locate the Major Constellations

1. Select a constellation from TAAS Fab 50 seasonal list. (see www.TAAS.org for the list). 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. 5. Look from the sky to the sky map to confirm you are viewing the correct constellation.

Fall Cassiopeia

Summer Scorpius

Spring Leo

Winter Orion

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.

What are we looking for in the night sky?

Object Naked eye Binocular Telescope 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

Few Many All

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. (www.TAAS.org) 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.

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

Sky Lesson 2.0

Looking south

Looking north

Apparent Daily Motions of the Night sky

To us the sky appears to rotate east to west

It is the earth that actually rotates west to east

Apparent motion right – to - left

Apparent motion left – to - right

Sky Lesson 2.1

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.

How far does a star move in 1 hour?

150 per hour

Sky Lesson 2.2

How far does a star move in 1 hour? (cont.) Sky Lesson 2.3

Looking North – motion counterclockwise Looking South – motion clockwise

Yearly Motion

Different times of the year different constellations are visible

Sky Lesson 2.4

Yearly Motion (cont.) Sky Lesson 2.5

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. (www.TAAS.org)

We will try to locate M 44 the “Beehive”

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

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.

The stars in Cancer are very dim

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

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

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.

Sky Lesson 3.0

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.)

Sky Lesson 3.1

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

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

Locating Polaris – our latitude is 350 N Polaris’ altitude is 350

Sky Lesson 3.4

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.

Sky Lesson 4.0

Magnitude (brightness) Sky Lesson 4.1

Magnitude (brightness) (cont.) Sky Lesson 4.3

The “size” of the dot represents the brightness of the star

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. (www.TAAS.org) 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.

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

We use angles to measure the distance across the night sky

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.

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.)

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.

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.

What is the Zenith?

The point in the sky directly above an observer.

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

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

Sky Lesson Two

1. Daily motion of the sky 2. Annual motion of the sky

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

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.

How far does a star move in 1 hour?

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.

Daily movement of the moon

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

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.)

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.”

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.

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.

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.

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

http://earthsky.org/space/what-is-the-ecliptic

cardinal headings

meridian

cardinal headings

meridian

zenith

meridian

zenith

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.

A way to find north

The pointer stars of the BIG DIPPER point to the north star

Apparent Motion of the Night sky

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.

Movement Between Nights The Earth orbits the Sun once every 365.25 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 365.25 days later. So, at the same time of night, a star moves its apparent position 360 / 365.25 = 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.

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.

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.

How to find the North Star

Two stars of the bowl always point to Polaris (north)

2. Establishing Awareness (establish your bearings).

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# 6. Locating Objects With Binoculars Sky Lesson 5 – FOV and Geometric Method

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

Navigating the Night Sky Checklist · Navigating the Night Sky Checklist 9 Procedures (P) P# 1....

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