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There Is Many Brand And Different Type Of Design Of Telescope. Basic Function Of A Telescope Is To Magnify The Object Seen And Also To Amplify The Brightness Of Object Seen. The Heart Of A Telescope Is The Mirror Lens That Collect The Light

 

Basic Understanding Of Telescope

  1. Design Of Telescope - Telescope Have 3 Primary Different Design : Refractor, Reflector And Also Catadioptric
  • Refractor Are Most Simple Design, Involving Focusing Incoming Light Source To Single Point. Large Objective Lens Gather Light And Focus It To Increase Image Detail And Brightness

Refractor Telescope

  • Refractor Provide Highest Contrast View Because Of No Central Obstruction, But Due To Design That Causes Light Refraction, This Will Scatter Light Of Different Colour Spectrum Resulting Chromatic Aberation (Colour Fringing) Best Optical Refractor Design Using Special Low Dispersion (ED) Glasses Will Reduce This Problem But Will Be More Costly


Chromatic Aberation Seen As Blue/Brown/Purple Colour Fringing


Reflector Telescope

  • Reflector Basically Are Reflection Mirror. Precision Polish Reflecting Mirror Will Focus Light From Mirror To Increase Image Brightness And Detail. Mirror Are Easier To Manufacture And Cost Less Than Lens (Bigger Aperature For Price). Reflector Does Not Suffer From Chromatic Aberation And Provide Almost Similar Contrast To Refractor. Reflector Can Be Built With Spherical, Hyperbolic Or Parabolic Mirror. Parabolic Mirror Can Give Diffraction Limited Optics But Cost More. Hyperbolic Are Special Design For Astrophotography Purpose. Spherical Mirror Gives Good Image If Focal Ratio Exceed F/10, Anything Under Will Require Spherical Lens Corrector (Known As Jones-Bird Newtonian)



Catadioptric Involve Folding Optical Path Multiple Time To Achieve Compact For Aperature Telescope

Catadioptric Telescope

  • Catadioptric Are Compound Telescope (Folding Optics). This Design Allow More Compact Telescope For Aperture. It Provides Chromatic Aberation Free Image. Catadioptric Design Has Relatively Large Central Obstruction And Reduce Contrast Slightly. Core Concept Of Definition Of Compound Telescope Is 2 Reflective Surface With Different Curvature Angle (Different F Ratio)

 

  1. Factor Determining Telescope Performance
  • Important Determination Of Telescope Performance Is Aperture (Size Of Objective). Bigger Aperature Allow Higher Light Collection And Image Resolution (Under Best Condition).
  • Central Obstruction Determine TContrast And Brightness Of Image
  • Light Gathering Power Determined By Aperture Of A Telescope. Higher Light Gathering Power Translate To Brighter Image Of Deep Space Object.
  • Resolution Of Telescope Is Determined By Aperture. Resolution Of Telescope Is Measure By Dawes Limit (Typical In Arc Second) A Smaller Dawes Limit Translate To Better Capability Of Telescope To Detect And Differentiate Fine Detail Of Objects
  • Optical Coating : Multi-Coated Lens Will Reduce Light Loss From Reflection Of Glass. In Refractor Telescope, Uncoated Glass Gives About 8% Light Loss, Where As Multi-Coated Refractor Loss Less Than 0.5% Of Total Light. In Case Of Reflector, Coating Quality Will Depends On Type Of Aluminium Used And Measured In Reflectivity Index. Best Reflectivity Index Is 99% Reflectivity
  • Optical Perfection : Mirror Or Lens Perfection Is Calculated Based On Diffraction Limit. Diffraction Limited Optics Translate To Almost Perfect Mirror, Where Maximum Resolution Is Possible With Usage Of Diffraction Limited Lens/Mirror.
  • Spherical Aberation : Mirror Or Lens Causes Deviation Of Light Pathway. A Spherical Imperfection Is Common In All Type Of Telescope Design, Unless Fully Corrected. Lowest Commercial Minimum Spherical Aberation Telescope Are Maksutov-Cassegrain Design

 

  1. Maximum Performance Of Telescope And How It Is Calculated
  • Magnification : Maximum Magnification Of Telescope Is Calculated Based On Aperature Of Telescope. General Rule Of 50-60x Per Inch (25.2mm) Of Aperature Is Maximum Magnification Of Given Telescope. 50mm Telescope Will Have 120x Maximum Magnification. 203mm (8'') Telescope Will Have 480x Maximum Magnification
  • Light Gathering Power : Light Gathering Power Will Translate To How Bright An Object Seen Via Telescope. Higher Light Gathering Power Allow Dimmer Objects Seen Brighter And With More Detail. Light Gathering Power Is calculated Based On Aperature (Size Of Telescope Lens/Mirror) 70mm Telescope Has 70x70/49 : 100x Light Gathering Power. 203mm (8'') Telescope Has 203x203/49 : 841x Light Gathering Power. Higher Light Gathering Power, Dimmer Deep Space Object Can Be Seen