What are the types of optical systems used for Celestron telescopes?

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	What are the types of optical systems used for Celestron telescopes?

Answer Here are brief descriptions of the eight major types, followed by lists by series and type for early 2011. Included are Sky-Watcher telescopes sold by Celestron.

Refractors
•Optical system: 2-element achromatic objective lens
•Aberrations: refractors have some color aberration especially at small f/ratios
•Advantages: easy to use, low maintenance, closed tube, no obstruction
•Disadvantages: chromatic aberration, available in small sizes up to 150mm aperture only

ED APO Refractors
•Optical system: 2-element low-dispersion ED objective lens
•Aberrations: very little chromatic aberration
•Advantages: easy to use, low maintenance, closed tube, no obstruction
•Disadvantages: available in small sizes up to 120mm aperture only, relative high cost

Newtonian Reflector
•Optical system: spherical or parabolic primary mirror, flat elliptical-shaped secondary mirror.
•Aberrations: coma away from central field of view especially at small f/ratios
•Advantages: relative low-cost
•Disadvantages: larger sizes bulky, central obstruction by secondary and support, unsuited for terrestrial viewing, back focus issues

Dobsonian Reflector
•Optical system: parabolic primary mirror, flat elliptical-shaped secondary mirror.
•Aberrations: coma away from central field of view especially at small f/ratios
•Advantages: relative low-cost
•Disadvantages: larger sizes bulky, central obstruction by secondary and support, unsuited for terrestrial viewing, back focus issues

Barlowed Newtonian Reflector
•Optical system: as with Newtonian except Barlow lens added in eyepiece drawtube
•Aberrations: coma away from central field of view especially at small f/ratios
•Advantages: relative low-cost, short tube for long effective focal length
•Disadvantages: central obstruction by secondary and support, unsuited for terrestrial viewing, back focus issues

Maksutov-Cassegrain Catadioptric (Mak)
•Optical system: spherical primary, spherical secondary spot on spherical meniscus corrector
•Aberrations: higher-order spherical aberrations in shorter f/ratios.
•Advantages: maintenance free, short closed tube for long effective focal length, relative low-cost
•Disadvantages: only available in sizes up to about 130mm and high f/ratios, central obstruction

Schmidt-Cassegrain Catadioptric (SCT)
•Optical system: spherical primary, spherical secondary, aspherical corrector plate
•Aberrations: some coma and field curvature in outer field
•Advantages: short closed tube for long effective focal length, versatile set-ups
•Disadvantages: central obstruction, relative high cost, relative high f/ratio

EdgeHD SCT
•Optical system: spherical primary, spherical secondary spot, aspherical corrector plate, two-element lens internal corrector
•Aberrations: essentially none
•Advantages: short tube for long effective focal length, flat coma-free field, versatile set ups
•Disadvantages: central obstruction, relative high cost, relative high f/ratio

PowerSeeker
Refractors 50AZ 60AZ 70AZ 60EQ 70EQ 80EQ	Newtonian Reflectors 114AZ 114EQ	Barlowed Newtonian Reflector 127EQ

AstroMaster
Refractors 70AZ 70EQ 90AZ 90EQ	Newtonian Reflectors 76EQ 130EQ	Barlowed Newtonian Reflector114EQ

Omni XLT
Refractors XLT102 XLT120 XLT150R	Newtonian Reflector XLT150	SCT XLT127

LCM
Refractors 60LCM 70LCM 80LCM 90LCM	Newtonian Reflector 76LCM	Barlowed Newtonian Reflector 114LCM

SLT
Refractor 102SLT	Newtonian Reflector 130SLT	Maks 90SLT 127SLT

SkyProdigy
Refractor 70	Newtonian Reflector 130	Mak 90

SE
Mak 4SE	SCTs 5SE 6SE 8SE

Advanced Series GT
Refractor C6-RGT	Newtonian Reflectors C6-NGT C8-NGT C10-NGT	SCTs C6-SGT C8-SGT C9.25-SGT C11-SGT

CPC

SCTs
800 GPS
925 GPS
1100 GPS

CGEM

SCTs
800
925
1100

CGEM - EdgeHD

EdgeHD SCTs
800 HD
925 HD
1100 HD

CGEM DX

SCTs
1100
1400

CGEM DX - EdgeHD

EdgeHD SCTs
1100 HD
1400 HD

CGE Pro

SCTs
925
1100
1400
1400 Fastar

CGE Pro - EdgeHD

EdgeHD SCTs
925 HD
1100 HD
1400 HD

Specialty Series
Refractors Travel Scope 50 Travel Scope 70 Ambassador 80AZ	Newtonian Reflector FirstScope

Sky-Watcher ED-APO PRO

ED-APO Refractors
80ED APO
100ED APO
120ED APO

Sky-Watcher Dobsonian

Dobsonian Reflectors
8”
10”
12”

Sky-Watcher Backpacker
Refractor 80R	Mak 90M

Article Details

Article ID:

2467

Created On:

Feb 17 2011 12:06 PM

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