Transcript Astronomy Part 1 - Malvern Troop 7

Astronomy
Merit Badge
Part I. Covered in the cabin
on Wednesday 16-Nov-2011
Review
Counselor Name: Niels Ryde
E-mail
[email protected]
We covered requirements 1 – 3 and 4 in part.
Scouts who are taking the Astronomy merit badge should start filling in the requirements
that we have covered. We will talk more about constellations next time, but everyone
should be able to do 1 – 3 in their workbooks.
The Astronomy merit badge booklet is available in Troop 7’s library in the cabin. Many
answers to the requirements can be found there.
Course curriculum
1. Describe the proper clothing and other precautions for safety making observations at night
In cold weather
How to safely observe the Sun, and objects near the Sun, and the Moon
Explain first aid for injuries or illnesses such as heat, cold reactions, dehydration, bites and
stings, and damage to your eyes that could occur during observation.
2. Explain what light pollution is
3. With the aid of diagrams (or real telescopes if available), do each of the following:
(a) Explain why binoculars and telescopes are important astronomical tools. Demonstrate
or explain how these tools are used.
(b) Describe the similarities and differences of several types of astronomical telescopes.
(c) Explain the purposes of at least three instruments used with astronomical telescopes.
Course curriculum
4. Do the following:
a) Identify in the sky at least 10 constellations, at least four of which are in the zodiac.
b) Identify at least eight conspicuous stars, five of which are of magnitude 1 or brighter.
c) Make two sketches of the Big Dipper. In one sketch, show the Big Dipper's
orientation in the early evening sky. In another sketch, show its position several
hours later. In both sketches, show the North Star and the horizon. Record the date
and time each sketch was made.
d) Explain what we see when we look at the Milky Way.
5. Do the following:
a) List the names of the five most visible planets. Explain which ones can appear in
phases similar to lunar phases and which ones cannot, and explain why.
b) Find out when each of the five most visible planets that you identified in
requirement 5a will be observable in the evening sky during the next 12 months,
then compile this information in the form of a chart or table. Update your chart
monthly to show whether each planet will be visible during the early morning or in
the evening sky.
Course curriculum
6. At approximately weekly intervals, sketch the position of Venus, Mars or Jupiter in relation
to the stars. Do this for at least four weeks and at the same time of night. On your sketch,
record the date and time next to the planet's position. Use your sketch to explain how
planets move.
7. Do the following:
a) Sketch the face of the moon and indicate at least five seas and five craters. Label
these landmarks.
b) Sketch the phase and the daily position of the Moon at the same hour and place, for
a week. Include landmarks on the horizon such as hills, trees, and buildings. Explain
the changes you observe.
c) List the factors that keep the Moon in orbit around Earth.
d) With the aid of diagrams, explain the relative positions of the Sun, Earth, and the
Moon at the times of lunar and solar eclipses, and at the times of new, first-quarter,
full, and last-quarter phases of the Moon.
8. Do the following:
a) Describe the composition of the Sun, its relationship to other stars, and some effects
of its radiation on Earth's weather. Define sunspots and describe some of the effects
they may have on solar radiation.
b) Identify at least one red star, one blue star, and one yellow star (other than the Sun).
Explain the meaning of these colors.
Course curriculum
9. With your counselor's approval and guidance, do ONE of the following:
a) Visit a planetarium or astronomical observatory. Submit a written report, a
scrapbook, or a video presentation afterward to your counselor that includes the
following information:
1. Activities occurring there
2. Exhibits and displays you saw
3. Telescopes and instruments being used
4. Celestial objects you observed.
b) Plan and participate in a three-hour observation session that includes using
binoculars or a telescope. List the celestial objects you want to observe, and find
each on a star chart or in a guidebook. Prepare an observing log or notebook. Show
your plan, charts, and log or notebook to your counselor before making your
observations. Review your log or notebook with your counselor afterward.
c) Plan and host a star party for your Scout troop or other group such as your class at
school. Use binoculars or a telescope to show and explain celestial objects to the
group.
d) Help an astronomy club in your community hold a star party that is open to the
public.
Course curriculum
9. With your counselor's approval and guidance, do ONE of the following:
e) Personally take a series of photographs or digital images of the movement of the
Moon, a planet, an asteroid or meteoroid, or a comet. In your visual display, label
each image and include the date and time it was taken. Show all positions on a star
chart or map. Show your display at school or at a troop meeting. Explain the changes
you observed.
10. List at least three different career opportunities in astronomy. Pick the one you in which
are most interested and explain how to prepare for such a career. Discuss with your
counselor what courses might be useful for such a career
1. Precautions for making observations at
night
Dress appropriately
You will be standing relatively still for possible a long time. In cold weather, dress as if it
was 10 – 20 F colder than it actually is. In the summer, make sure to wear insect
repellant, no open toe shoes (sandals). Ideally, survey the area you are going to be
observing in during daylight. Bring flashlights and red covered flashlights.
Safety
Never observe the sun directly, never look at the sun through binoculars, sunglasses are
not sufficient protection. Very dark filters such as welders glass are adequate for looking
at the sun. The best way is through indirect projection. For objects near the sun (such as
Mercury), only observe as long as the sun is entirely below the horizon. The same
precaution would apply to a new moon.
Recognize the signs of heat stroke. Best way to avoid, bring water on warm summer
nights (see scout book first aid section, 150-152).
2. Light Pollution
Sky glow over Manhattan
Rural town (top)
Metropolitan area (bottom)
http://www.cleardarksky.com/c/WstChstrPAkey.html?1
2. Light Pollution, cont’d
What it is
Light pollution (for astronomers), is the result of too much artificial light. This is
usually caused by the glare of street lights, parking lights, outdoor signs, etc. A
full moon will also contribute to sky glow (light pollution) at an intensity similar
to that of urban lights.
Light pollution reduces ones ability to see faint objects such as faint stars,
nebulas and galaxies.
What to do about it
Choose your location
Observe the skies late at night (as businesses close and people go to be, lights
tends to be less intrusive).
Avoid observing near the times of a full moon (unless you want to observe the
moon of course)
Choose objects fairly high in the sky.
Choose brighter objects (there are many that offer spectacular viewing)
2. Light Pollution, cont’d
2. Light Pollution, cont’d
Show coords:
On
click: N40.793, W75.81
link
roadmap
link
topomap
Open in
find new
charts window/tab
Get this map as a Google Earth image overlay.
(Download full map130meg after decompression.)
mi
mi
http://www.cleardarksky.com
2. Light Pollution, cont’d
Bortle
Color Scale
Description (Descriptions are approximate. Your sky may vary.)
approx
1
Gegenschein visible. Zodiacal light annoyingly bright. Rising milkyway confuses some into thinking it's
dawn. Limiting magnitude 7.6 to 8.0 for people with exceptional vision. Users of large dobsonian
telescopes are very happy.
2
Faint shadows cast by milkyway visible on white objects. Clouds are black holes in the sky. No light
domes. The milky way has faint extentions making it 50 degrees thick. Limiting magntiude 7.1 to 7.5.
3
Low light domes (10 to 15 degrees) on horizon. M33 easy with averted vision. M15 is naked eye. Milky
way shows bulge into Ophiuchus. Limiting magnitude 6.6 to 7.0.
4
Zodiacal light seen on best nights. Milkyway shows much dark lane structure with beginnings of faint bulge
into Ophiuchus. M33 difficult even when above 50 degrees. Limiting magnitude about 6.2 to 6.5.
4.5
Some dark lanes in milkyway but no bulge into Ophiuchus. Washed out milkyway visible near horizon.
Zodiacal light very rare. Light domes up to 45 degrees. Limiting magnitude about 5.9 to 6.2.
5
Milkyway washed out at zenith and invisible at horizon. Many light domes. Clouds are brighter than sky.
M31 easily visible. Limiting magnitude about 5.6 to 5.9.
6 or 7
Milkyway at best very faint at zenith. M31 difficult and indestinct. Sky is grey up to 35 degrees. Limiting
magntidue 5.0 to 5.5.
8 or 9
Entire sky is grayish or brighter. Familliar constellations are missing stars. Fainter constellations are absent.
Less than 20 stars visible over 30 degrees elevation in brigher areas. Limiting magntude from 3 to 4. Most
people don't look up. CCD imaging is still possible. But telescopic visual observation is usually limited to
the moon, planets, double stars
2. Light Pollution, cont’d
French Creek State Gamelands Light Pollution Map
Light pollution limits the visibility of milky way to the unaided eye, the visiblity of nebulae and
galaxies seen in telescopes, and raises the noise on CCD astrophotographs. Only the observation
of planets and double stars is unaffected. Low light pollution conditions, or dark skies, is one of
the most important properties of a good astronmical observing site.
Observations indicate that the lightpollution color code for this site is closer to:
mi
http://www.cleardarksky.com
mi
Some dark lanes in milkyway but no bulge into Ophiuchus. Washed out milkyway visible near
horizon. Zodiacal light very rare. Light domes up to 45 degrees. Limiting magnitude about 5.9 to
6.2.
2. Light Pollution, cont’d
Blue Mountain Vista Observatory Light Pollution Map
Light pollution limits the visibility of milky way to the unaided eye, the visiblity of nebulae and
galaxies seen in telescopes, and raises the noise on CCD astrophotographs. Only the observation of
planets and double stars is unaffected. Low light pollution conditions, or dark skies, is one of the
most important properties of a good astronmical observing site.
Get this map as a Google Earth image overlay.
(Download full map130meg after decompression.)
http://www.cleardarksky.com
3.a Tools of the Trade
Magnitude
Why are binoculars and telescopes important tools for astronomers?
The ability to see faint objects, larger aperture means more light.
Magnification, higher magnification means more detail.
f1 = focal length of objective
Limiting magnitude = 1.9 + 2.5 * Log10(D2)
f2 = focal length of eye piece
Aperture
50 mm
100 mm
200 mm
400 mm
Limiting magnitude, mc = 5, E = 6 mm
11.2
12.1
13.3
14.9
3.b Types of Telescopes
3.b.a Refracting telescopes
Lenses only
3.b.b Reflecting telescopes
Mirrors (and eye piece)
3.b.c. Catadioptic telescopes
Lens and mirrors (and eye piece)
3.b.a Refracting Telescopes
Advantages
Dissadvantages
Robust design, good images.
Tend to be expensive for apertures
larger than 120 mm
Easy to use, rarely needs collimation
Telescopes with long focal length are
difficult to work with, and requires
extremely sturdy mount.
Longer focal length gives better
contrast while APO/ED telescopes are
shorter and are more portable
All refractors, except very pricy APO
designs, exhibit some level of
chromatic aberration.
Smaller refractors are more affordable.
These are common entry level
telescopes
Smaller refractors are not ideal for faint
objects, such as nebulas and galaxies.
3.b.a Refracting Telescopes
3.b.b Reflecting Telescopes
Newton Reflector
Advantages
Dissadvantages
Best value per inch of aperture
Not good for terrestrial observation.
No chromatic aberration. Larger field of Coma effect at edge of field of view.
view than other telescopes of similar
focal length.
Conveniently located eye piece
The eye piece may be difficult to reach
on larger scopes.
Reasonably compact up to 1000 mm
focal length
Need to collimate the scope from time
to time
Excellent for faint objects
Open tube means that dust can readily
reach the mirror.
3.b.b Reflecting Telescopes
Newton Reflector
Cassegrain Reflector
Ritchey Cretien
3.b.c Catadioptic Telescopes
The Schmidt–Cassegrain design is very
popular with consumer telescope
manufacturers because it combines easy
to manufacture spherical optical surfaces
to create an instrument with the long
focal length of a refracting telescope with
the lower cost per aperture of a
reflecting telescope.
3.c Instruments in Astronomy
Spectroscope
Presents the spectrum from a star
Filar micrometer
Special eye piece that measures the distance between
double stars.
Photometer
Measures the brightness of light from a star.
First Time Telescope Buyers
FYI only. Not required for merit badge
First Time Telescope Buyers
Advice for First Time Telescope Buyers (http://www.skiesunlimited.net/)
1. Will you be satisfied with just the moon and planets? Does your passion include
deep space objects such as star clusters, nebulae and distant galaxies? Would
you favor a dual purpose instrument that also allows you to observe birds and
other wildlife or boats out on the water?
2. Does the telescope need to be portable enough to transport to a dark site? Some
types of telescopes are inherently more portable than others. Don't buy more
telescope than you can comfortably handle.
3. Are you the type of person who has the patience to track down celestial targets
on your own, or do you require the assistance of a computerized "go-to"
telescope to locate objects for you? If you are a beginner or live in a highly light
polluted urban environment, then a go-to telescope may well be your best
option.
FYI only. Not required for merit badge
Which Scope to Buy
( From Ed. Ting’s web page http://www.scopereviews.com/begin.html)
4.5" or 6" reflectors make excellent beginner's instruments. For $300-$650,
you get a decent aperture and a scope that's relatively portable. On the
refractor side, look for an 80 mm scope on a stable mount.
Avoid department store, toy store, and "Nature/Science" store telescopes.
The primary purpose of a telescope is to gather light. Thus, all other things
being equal, beginners should buy the largest aperture telescope they can
afford. A 6" Dobsonian reflector is an excellent first telescope.
BUT, if the instrument is too large, you may never use it. Be realistic about
what you're willing to lug around.
You don't need more than 3 or 4 carefully chosen eyepieces in your
collection at first. The minimum quality you should consider are Kellners
(and their offshoots). A barlow is useful tool for doubling your collection at
minimal cost.
FYI only. Not required for merit badge
Telescopes
Starter scopes
Celestron AstroMaster 90AZ
Meade StarNavigator 102
FYI only. Not required for merit badge
Celestron NexStar 5SE
Useful links
http://www.cleardarksky.com/c/WstChstrPAkey.html?1
http://www.cruxis.com/scope/limitingmagnitude.htm
http://www.skiesunlimited.net
http://www.scopereviews.com/begin.html
4.a Constellations
Identify at least 10 constellations in the sky, of which at
least four are in the zodiac.
All year round constellations (circumpolar) {Decl ≥90-Lat.}
Ursa Major, Ursa Minor, Cassiopeia, Draco, Cepheus
Seasonal
Spring
Summer Autumn Winter
Leo
Virgo
Libra
Cancer
Lyra
Pegasus Orion
Cygnus Andromeda
Aquila Perseus Gemini
Scorpius Aries
Auriga
Sagittarius
Pisces
Capricorneus
Aquarius
Canis Major
Taurus
Zodiac signs
Constellations in a band (± 8 deg) around the ecliptic
№ Symbol Long. Latin name
English translation
1
♈
0°
Aries
The Ram
2
♉
30°
Taurus
The Bull
3
♊
60°
Gemini
The Twins
4
♋
90°
Cancer
The Crab
5
♌
120°
Leo
The Lion
6
♍
150°
Virgo
The Maiden
7
♎
180°
Libra
The Scales
8
♏
210°
Scorpio
The Scorpion
9
♐
240°
Sagittarius
The (Centaur) Archer
10 ♑
270°
Capricorn
"Goat-horned" (The SeaGoat)
11 ♒
300°
Aquarius
The Water-Bearer
12 ♓
330°
Pisces
The Fish