astronomy gear for beginners

Astronomy Gear for BeginnersAstronomy Gear for Beginners

Nate Perkins and Greg HalacNate Perkins and Greg HalacNorthern Colorado Astronomical SocietyNorthern Colorado Astronomical Society7 December 20067 December 2006

7 December 20067 December 2006 22

Goals for the TalkGoals for the Talk

How to get startedHow to get startedWhat are the What are the ““justjust--startingstarting”” essentials?essentials?Learn about basic telescope designsLearn about basic telescope designsLearn about useful accessoriesLearn about useful accessoriesWhat will I be able to see?What will I be able to see?Common misconceptions & pitfallsCommon misconceptions & pitfalls


OutlineOutlineInitial considerationsInitial considerationsBasic opticsBasic opticsBinoculars and TelescopesBinoculars and TelescopesTelescope mountsTelescope mountsEyepiecesEyepiecesBasic Basic ““mustmust--havehave”” itemsitemsBuying a first telescope Buying a first telescope Support from othersSupport from others


Initial ConsiderationsInitial Considerations


Initial ConsiderationsInitial ConsiderationsAge, ability & patienceAge, ability & patience

How much weight can be comfortably lifted?How much weight can be comfortably lifted?Can user operate the scope without assistance?Can user operate the scope without assistance?Expected duration of observing sessions Expected duration of observing sessions ––minutes to all night?minutes to all night?

Lou Church, 17Lou Church, 17””Meade refractor, Meade refractor, Prairie Skies 2005Prairie Skies 2005

1818”” Obsession Obsession reflectorreflector

1010”” Orion Orion reflectorreflector

80mm refractor 80mm refractor on camera tripodon camera tripod

50mm binoculars50mm binoculars


Initial ConsiderationsInitial ConsiderationsUser BackgroundUser Background

Interest & Interest & experienceexperience

Has user developed Has user developed a basic knowledge of a basic knowledge of astronomy?astronomy?Has astronomy been Has astronomy been a longa long--term interest term interest (1 year or more)?(1 year or more)?Enjoys observing Enjoys observing even if only looking even if only looking at previously seen at previously seen objectsobjects


Initial ConsiderationsInitial ConsiderationsUser BackgroundUser Background

Technical aptitudeTechnical aptitudeBuy or build a scope?Buy or build a scope?Comfortable using basic tools?Comfortable using basic tools?

Commercially Commercially avaliableavaliable 80mm refractor 80mm refractor on camera tripod (Orion Telescopes)on camera tripod (Orion Telescopes)

A Dobsonian telescope under A Dobsonian telescope under construction (NCAS)construction (NCAS)

An enterprising young An enterprising young telescope maker (telescope maker (StellafaneStellafane))


Initial ConsiderationsInitial ConsiderationsViewing EnvironmentViewing Environment

Viewing sitesViewing sitesDistance, facilities?Distance, facilities?Dark, suburban, urban skies?Dark, suburban, urban skies?

Weather conditionsWeather conditionsTemperature throughout the yearTemperature throughout the yearHumidityHumidityWind

CheyenneCheyenne

Fort CollinsFort Collins

GreeleyGreeley

DenverDenver

WindDark Sky map centered on Fort CollinsDark Sky map centered on Fort Collins

Viewing from a Dark Sky site is like adding an extra 2-4 inches to your telescope size!

NCAS NCAS ““darkdark”” sky site at Pawnee Grasslandssky site at Pawnee Grasslands


Initial ConsiderationsInitial Considerations

Weekend Under the Stars, summer 2006Weekend Under the Stars, summer 2006

Support available?Support available?ExpertsExpertsWeb accessWeb access

Group or solo activityGroup or solo activity

Rocky Mountain National Park Rocky Mountain National Park StarwatchStarwatch, , summer 2006summer 2006 RMNP, summer 2006RMNP, summer 2006


Optics Optics -- BasicsBasics


Optics Optics –– BasicsBasicsA telescopeA telescope’’s main lens / mirror is called the s main lens / mirror is called the ““ObjectiveObjective”” / / ““PrimaryPrimary””The objective lens is designed to:The objective lens is designed to:

Collect light from faint objects (galaxies, nebula, star clusterCollect light from faint objects (galaxies, nebula, star clusters)s)Observe fine details (moon, planets, closelyObserve fine details (moon, planets, closely--spaced stars)spaced stars)

RefractorRefractor objective Reflector objective

Reflector


Optics Optics –– BasicsBasicsWithout optical aid, the eye collects light through the Without optical aid, the eye collects light through the pupil (~5pupil (~5--7mm in diameter fully dilated)7mm in diameter fully dilated)Compared to the unaided eye (~6mm pupil diameter):Compared to the unaided eye (~6mm pupil diameter):

88””=200mm objective collects ~1000x more light =200mm objective collects ~1000x more light –– LightLight gathering gathering is proportional to area of the objectiveis proportional to area of the objective88””=200mm objective can resolve features ~30x smaller =200mm objective can resolve features ~30x smaller ––Resolving power is inversely proportional to diameterResolving power is inversely proportional to diameter

Some light (~0.5 Some light (~0.5 –– 5 %) is lost at 5 %) is lost at everyevery optical surfaceoptical surface

88”” mirror mirror –– 1000x the eye1000x the eye 1414”” mirror mirror –– 3500x the eye3500x the eyeHuman eye ~ 6mm darkHuman eye ~ 6mm dark


Optics Optics –– BasicsBasicsThe The ““Focal LengthFocal Length”” of an objective/primary is the of an objective/primary is the distance to the point where light from a star focusesdistance to the point where light from a star focuses

The The ““ff--ratioratio”” of an objective/primary is the focal length of an objective/primary is the focal length divided by the diameter. (As in photography, the image divided by the diameter. (As in photography, the image brightness increases as the fbrightness increases as the f--ratio decreases.)ratio decreases.)Small fSmall f--ratio (< f/5) optics usually show more distortion ratio (< f/5) optics usually show more distortion and/or cost more than large fand/or cost more than large f--ratio (> f/8) designsratio (> f/8) designs


Optics Optics –– BasicsBasicsMagnification of a telescope isMagnification of a telescope is

Maximum useable magnification is ~50x the Maximum useable magnification is ~50x the objective diameter (in inches) with objective diameter (in inches) with GREATGREATconditions conditions …… ~20x more common~20x more commonOptical imperfections/obstructions degrade Optical imperfections/obstructions degrade image sharpness and contrastimage sharpness and contrastAtmospheric turbulence critically affects image Atmospheric turbulence critically affects image quality for the moon, planets, and double starsquality for the moon, planets, and double stars

calLengthEyepieceFoocalLengthObjectiveFionMagnificat =

Magnification is one of the LEAST important things to look for in a telescope! Too much magnification always results in worse images.

Jupiter, with Jupiter, with appropriate appropriate

magnificationmagnification

Jupiter, with Jupiter, with excessive excessive

magnificationmagnification


Types of Astronomy GearTypes of Astronomy Gear


BinocularsBinocularsHighly recommended for learning Highly recommended for learning

the night sky. Gorgeous views of the night sky. Gorgeous views of Milky Way from darkMilky Way from dark--sky sites.sky sites.

Pros:Pros:Inexpensive for usable qualityInexpensive for usable qualityVery wide field viewsVery wide field views22--eye viewingeye viewing““CorrectCorrect”” (non(non--inverted) viewsinverted) views

Cons:Cons:Hard to handHard to hand--hold at >10X powerhold at >10X powerLimited lightLimited light--gatheringgathering


Telescopes Telescopes -- RefractorRefractor

Example of chromatic Example of chromatic abberationabberation

First astronomical telescope design First astronomical telescope design ––applied by Galileo, 1609 ~20mm, 8xapplied by Galileo, 1609 ~20mm, 8x

Common types:Common types:AchromatAchromat –– ““approximatelyapproximately”” color color correct, worse in short focal lengthscorrect, worse in short focal lengthsApochromatApochromat –– uses low dispersion uses low dispersion lenses, very expensivelenses, very expensive

Pros:Pros:AdjustmentAdjustment--free, sealed tubefree, sealed tube

Cons:Cons:Expensive for high quality opticsExpensive for high quality opticsExpensive for large (>4Expensive for large (>4””) aperture) apertureColor fringing on Color fringing on ““cheapcheap”” opticsopticsLarge apertures not very portable Modern refractorModern refractorGalileoGalileo’’s s

telescopestelescopes

Large apertures not very portable


Telescopes Telescopes -- ReflectorReflectorSecond type of astronomical telescope Second type of astronomical telescope

–– Sir Sir IssacIssac Newton, 1671Newton, 1671

Pro:Pro:Largest aperture for moneyLargest aperture for moneyNo chromatic aberrationNo chromatic aberration

Con:Con:Precise alignment (Precise alignment (““collimationcollimation””) ) required for optimal imagingrequired for optimal imagingInherent coma, worse at short focal Inherent coma, worse at short focal lengthslengthsEyepiece position for highEyepiece position for high--up objects up objects may require ladder for large scopesmay require ladder for large scopesOptics exposed to environmentOptics exposed to environmentNot suitable for terrestrial viewingNot suitable for terrestrial viewing

Modern Dobsonian (Newtonian)Modern Dobsonian (Newtonian)

NewtonNewton’’s 6s 6”” reflector reflector


Telescopes Telescopes -- CatadioptricCatadioptricCombination of mirrors and lenses Combination of mirrors and lenses ––

many different variantsmany different variants

Pros:Pros:Compact tubeCompact tubeTube is closedTube is closedNeeds little collimationNeeds little collimation

Cons:Cons:Relatively expensive for apertureRelatively expensive for apertureDew condenses easily on front Dew condenses easily on front correctorcorrectorProne to Prone to ““image shiftimage shift””Relatively large central obstruction

SchmidtSchmidt--CassegrainCassegrain

Relatively large central obstruction MaksutovMaksutov--CassegrainCassegrain


““SmallSmall”” Aperture TelescopesAperture TelescopesFeatureFeature

RefractorRefractor33”” –– 44””

ReflectorReflector33”” –– 66””

CatadioptricCatadioptric3.53.5”” -- 55””

Price RangePrice Range $200 $200 -- $800$800 $120 $120 -- $1000$1000 $500$500--$4300$4300

PortabilityPortability Excellent Excellent Excellent

Ease of setupEase of setup Good Very good Very good

Ease of useEase of use Good Very good Good

Moon viewsMoon views Excellent Excellent Excellent

Planet viewsPlanet views Very good Very good Good

Galaxy/Nebula view Galaxy/Nebula view Fair Fair Fair

Double star viewsDouble star views Very good Very good Good

Comet viewsComet views Fair Fair Fair


““MediumMedium”” Aperture TelescopesAperture TelescopesFeatureFeature

RefractorRefractor44”” –– 55””

ReflectorReflector88”” –– 12.512.5””

CatadioptricCatadioptric66”” –– 88””

Price RangePrice Range $700 $700 -- $10,000$10,000 $400 $400 -- $14,000$14,000 $1000 $1000 -- $4000$4000

PortabilityPortability Very good Fair Very good

Ease of setupEase of setup Excellent Fair Very good

Ease of useEase of use Very good Very good Very good

Moon viewsMoon views Excellent Excellent Excellent

Planet viewsPlanet views Very good Very good Good

Galaxy/Nebula view Galaxy/Nebula view Good Very good Good

Double star viewsDouble star views Very good Very good Very good

Comet viewsComet views Very good Very good Good


““LargeLarge”” Aperture TelescopesAperture TelescopesFeatureFeature RefractorRefractor

55”” -- 88””ReflectorReflector

1313”” and upand upCatadioptricCatadioptric

99”” -- 1414””

Price RangePrice RangeAchromat: $800Achromat: $800--$3200$3200Apochromat: $5000+Apochromat: $5000+

$1200 $1200 -- $36,000+$36,000+ $1700 $1700 -- $20,000+$20,000+

PortabilityPortability Fair Fair Poor

Ease of setupEase of setup Good -- Fair Poor Fair

Ease of useEase of use Very good Good Good

Moon viewsMoon views Excellent Very good Very good

Planet viewsPlanet views Excellent Excellent Very good

Galaxy/Nebula view Galaxy/Nebula view Good Excellent Very good

Double star viewsDouble star views Excellent Excellent Very good

Comet viewsComet views Very good Excellent Very good


Telescope MountsTelescope Mounts


Telescope MountsTelescope MountsA bad mount makes the best optics useless:A bad mount makes the best optics useless:

Movement magnified by scope powerMovement magnified by scope powerFlimsy mount vibrates in the wind or after being touchedFlimsy mount vibrates in the wind or after being touchedPoorly damped vibration blurs out detailsPoorly damped vibration blurs out detailsConsider range of viewing heights/positions for objects Consider range of viewing heights/positions for objects near horizon and near zenith near horizon and near zenith –– most scope/mount most scope/mount combinations make viewing some part of the sky combinations make viewing some part of the sky awkward.awkward.


Telescope Mounts Telescope Mounts –– AltAlt--azimuthazimuth

Classic altClassic alt--azaz mountmount

““AltitudeAltitude”” axis used to point up axis used to point up and downand down““AzimuthAzimuth”” axis rotates scope axis rotates scope from side to sidefrom side to sideStandard mount for Standard mount for ““DobsonianDobsonian”” reflectorsreflectorsCommon for catadioptric Common for catadioptric scopes scopes Tracking celestial objects Tracking celestial objects requires motion in both axesrequires motion in both axesConvenient for terrestrial Convenient for terrestrial viewingviewing

Dobsonian mountDobsonian mount


Telescope Mounts Telescope Mounts –– EquatorialEquatorialOne axis (One axis (““Right AscensionRight Ascension””) ) aligned parallel to earthaligned parallel to earth’’s axis s axis ––enables the scope to track with the enables the scope to track with the rotation of the starsrotation of the starsTracking celestial objects requires Tracking celestial objects requires motion in right ascension only motion in right ascension only ––easy to driveeasy to driveSecond axis (Second axis (““DeclinationDeclination””) used ) used to rotate scope away from celestial to rotate scope away from celestial pole (<1pole (<1°° from the North Star)from the North Star)Requires some familiarity to use

Classic German equatorialClassic German equatorial

Requires some familiarity to use

WedgeWedge--fork for equatorial drivefork for equatorial drive


Telescope Mounts Telescope Mounts –– ““GoGo--ToTo””Typically require manual centering Typically require manual centering on ~3 known objectson ~3 known objects““CheapCheap”” mounts not known for mounts not known for accuracyaccuracyIf on a first scope, owners tend to If on a first scope, owners tend to not learn their way around night not learn their way around night skyskyGood mounts enable seeing a lot Good mounts enable seeing a lot of objects in a relatively short time

SCT goto fork mount

of objects in a relatively short time

High end refractor equatorial mount


Eyepieces and AccessoriesEyepieces and AccessoriesEyepiecesEyepieces -- many designs, many designs, some costing hundreds of some costing hundreds of dollars!dollars!

Eyepieces such as Eyepieces such as KellnerKellner or or RamsdenRamsden are not usually advisedare not usually advisedPlosslsPlossls and and orthoscopicsorthoscopics are are good budget eyepiecesgood budget eyepieces

Barlow lensBarlow lens -- increases increases magnification from 2x to 3x. magnification from 2x to 3x. Doubles your effective number Doubles your effective number of eyepieces!of eyepieces!Colored filtersColored filters -- for enhanced for enhanced views of the planets and moonviews of the planets and moonLight pollution filtersLight pollution filters -- make make some nebulae more distinctsome nebulae more distinct


Basic Basic ““MustMust--HaveHave”” ItemsItems

Clothing for Clothing for 2020°°F colderF colder than the forecast than the forecast low:low:Gloves Gloves –– especially the type that have thin fingers or especially the type that have thin fingers or removable fingertipsremovable fingertipsHat! Hat! …… and something to cover the neckand something to cover the neckThermal underwear Thermal underwear –– the the ““layeredlayered”” method used by method used by hikers and hikers and skiiersskiiers is best is best –– look for the wicking type such look for the wicking type such as Merino wool, silk, or wicking syntheticsas Merino wool, silk, or wicking syntheticsWarm socks/boots Warm socks/boots –– wool socks with silk liners are great!wool socks with silk liners are great!


Basic Basic ““MustMust--HaveHave”” ItemsItemsEssentialsEssentials

Red LED flashlight and spare batteries. The type with a Red LED flashlight and spare batteries. The type with a thumbwheel to adjust brightness is best.thumbwheel to adjust brightness is best.Star atlasStar atlas

PlanispherePlanisphereBasic atlas such as the Cambridge Star AtlasBasic atlas such as the Cambridge Star AtlasAdvanced atlas (Sky Atlas 2000, etc)Advanced atlas (Sky Atlas 2000, etc)

Table and/or chair. Adjustable chairs such as the Table and/or chair. Adjustable chairs such as the StarboundStarbound chair are excellent. A drummerchair are excellent. A drummer’’s stool will s stool will work in a pinch depending on your scope height.work in a pinch depending on your scope height.Basic hand tools for your telescope and mountBasic hand tools for your telescope and mount


How Much to Spend?How Much to Spend?$25 or less:$25 or less:

Join an astronomy clubJoin an astronomy club

$200 or less:$200 or less:Telescopes generally Telescopes generally NOTNOT recommendedrecommendedBuy binoculars and other essentialsBuy binoculars and other essentials

$300 $300 -- $500:$500:Reasonable 3Reasonable 3”” –– 44”” refractor orrefractor or66”” –– 88”” Dobsonian reflectorDobsonian reflectorCan enjoy sky for several years before Can enjoy sky for several years before ““aperture feveraperture fever””likelylikely


Caution Advised Caution Advised ……ANY telescope that:ANY telescope that:

exceeds physical capability (strength, height, dexterity) exceeds physical capability (strength, height, dexterity) of the intended userof the intended usertouts its magnificationtouts its magnificationuses eyepiece diameters which do not match the uses eyepiece diameters which do not match the standard (1standard (1¼”¼”, 2, 2””))has a mount that shakes or doesnhas a mount that shakes or doesn’’t move smoothlyt move smoothly

Disappointment and little use (or resale value) are likely for:Disappointment and little use (or resale value) are likely for:Binoculars <$50 or magnification >10XBinoculars <$50 or magnification >10XRefractors <$300 or <3Refractors <$300 or <3”” apertureapertureReflectors <$300 or <4Reflectors <$300 or <4¼”¼” apertureapertureCatadioptric <$300 or <3Catadioptric <$300 or <3½”½” apertureaperture


But remember But remember ……

Any telescope that you enjoy Any telescope that you enjoy –– and use and use often often –– is a good telescope!is a good telescope!


Where to Buy?Where to Buy?

Local storesLocal storesJaxJax Outdoor GearOutdoor Gear

““BeginnerBeginner--friendlyfriendly”” Internet / MailInternet / Mail--order (in order (in alphabetic order):alphabetic order):Anacortes TelescopesAnacortes TelescopesAstronomicsAstronomicsOrion Telescopes & BinocularsOrion Telescopes & Binoculars


Recommend Recommend ……Spend time with other amateur astronomers:Spend time with other amateur astronomers:

most are happy to provide views thru their equipmentmost are happy to provide views thru their equipmentsee how easy/difficult it is to set up various scopessee how easy/difficult it is to set up various scopesdevelop your observing skillsdevelop your observing skillsfind out what both you and they like and whyfind out what both you and they like and whyfind out what both you and they find out what both you and they dislikedislike and whyand whyask questions!ask questions!

Use available Internet resources:Use available Internet resources:Astronomical LeagueAstronomical LeagueAstronomy publicationsAstronomy publicationsAstronomy clubsAstronomy clubs


In closing In closing ……Thank you, good luck, and dark skiesThank you, good luck, and dark skies

astronomy gear for beginners

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