AstronomyMerit Badge

Part I. Covered in the cabin on Wednesday 16-Nov-2011

Review

Counselor Name: Niels RydeE-mail ryde@comcast.net

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 curriculum1. Describe the proper clothing and other precautions for safety making observations at night

In cold weatherHow to safely observe the Sun, and objects near the Sun, and the MoonExplain 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 curriculum4. 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 curriculum6. 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 curriculum9. 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 curriculum9. 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 appropriatelyYou 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.

SafetyNever 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 isLight 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 itChoose your locationObserve 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

On click:

Show coords: N40.793, W75.81

link roadmap

link topomap

find charts

Open in new window/tab

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Get this map as a Google Earth image overlay. (Download full map130meg after decompression.)

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http://www.cleardarksky.com

2. Light Pollution, cont’d

Color Bortle Scale approx

Description (Descriptions are approximate. Your sky may vary.)

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’dFrench 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:

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http://www.cleardarksky.com

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’dBlue 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

f1 = focal length of objective

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

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.

Limiting magnitude = 1.9 + 2.5 * Log10(D2)

Microsoft Word DocumentMagnitude

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

Advantages Dissadvantages

Best value per inch of aperture Not good for terrestrial observation.

No chromatic aberration. Larger field of view than other telescopes of similar focal length.

Coma effect at edge of field of view.

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.

Newton Reflector

3.b.b Reflecting TelescopesNewton 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

SpectroscopePresents the spectrum from a star

Filar micrometerSpecial eye piece that measures the distance between

double stars.

PhotometerMeasures the brightness of light from a star.

First Time Telescope Buyers

FYI only. Not required for merit badge

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.

First Time Telescope Buyers

FYI only. Not required for merit badge

( 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.

Which Scope to Buy

FYI only. Not required for merit badge

Telescopes

Celestron AstroMaster 90AZ Meade StarNavigator 102

Starter scopes

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

SeasonalSpring Summer Autumn WinterLeo Lyra Pegasus OrionVirgo Cygnus Andromeda Canis MajorLibra Aquila Perseus GeminiCancer Scorpius Aries Auriga

Sagittarius Pisces TaurusCapricorneusAquarius

№ 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 Sea-Goat)

11 ♒ 300° Aquarius The Water-Bearer

12 ♓ 330° Pisces The Fish

Zodiac signs

Constellations in a band (± 8 deg) around the ecliptic