Transcript Motions in the Night Sky

Navigating the Night Sky Checklist
Observe
Educate
Have Fun
TAAS General Meeting April 4, 2015
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
3 months later
$$ = telescope
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
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# 7. Locating Objects With Pointing Devices
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
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# 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
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)
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?
that we place on the celestial sphere
4. What is the ecliptic?
to help us get our bearings.
5. What is the Zenith?
6. What is the Meridian?
Sky Lesson 1.1
What is the celestial sphere?
It is the inside surface of
To help us navigate the night sky,
we will “place” imaginary markers
on this sphere
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
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.
Sky Lesson 1.3
The Imaginary Markers (cont.)
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.
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.
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)
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)
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
South
Most accurate
In January at
10 pm
At other times
and dates, the
situation is
different
A little less accurate during other months at 10 pm
Easterly
Easterly
Westerly
December
Westerly
March
Orion is so prominently visible in the night sky
that the relationship is still useful.
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?
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.
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.
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)
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.
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.
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.
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.
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.
P# 4. Visually Locate the Major Constellations
1. Select a constellation from TAAS Fab 50 seasonal list.
(see www.TAAS.org 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.
Spring
Leo
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.
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
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
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
This completes Checklist P# 4
P# 4. Visually Locate the Major Constellations
1. Select a constellation from TAAS Fab 50 seasonal list.
(see www.TAAS.org 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.
Spring
Leo
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.
Summer Scorpius
Fall Cassiopeia
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
Few
Many
All
Moon
X
X
X
Planets
X
X
X
X
X
Globular Clusters
Open Clusters
X
X
X
Galaxies
X
X
X
Nebulas
X
X
X
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 2.0
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
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
Sky Lesson 2.2
How far does a star move in 1 hour?
150 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.
Sky Lesson 2.3
How far does a star move in 1 hour? (cont.)
Looking North – motion counterclockwise
Looking South – motion clockwise
Sky Lesson 2.4
Yearly Motion
Different times of the year different constellations are visible
Yearly Motion (cont.)
Sky Lesson 2.5
Feb
May
Aug
Nov
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)
P# 5. Locating Objects With the Naked Eye (cont.)
We will try to locate M 44 the “Beehive”
P# 5. Locating Objects With the Naked Eye (cont.)
2. Identify the constellation that the naked
eye object is in.
Cancer
3. Using your sky map or planisphere , locate
the constellation in the night sky.
The stars in Cancer
are very dim
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
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
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.
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.)
Sky Lesson 3.2
We use angles to measure the distance across the night sky (cont.)
300
Sky Lesson 3.3
We use angles to measure the distance across the night sky (cont.)
Sky Lesson 3.4
Locating Polaris – our latitude is 350 N
Polaris’ altitude is 350
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.
Sky Lesson 4.1
Magnitude (brightness)
Sky Lesson 4.3
Magnitude (brightness) (cont.)
The “size” of the dot represents the brightness of the star
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. (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.
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.
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.
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.
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.
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
cardinal headings
meridian
cardinal headings
meridian
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
east
of the
Night sky
south
north
west
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.
2. Establishing Awareness (establish your bearings).
How to find the North Star
Two stars of the bowl always point to Polaris (north)
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# 7. Locating Objects With Pointing Devices
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
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