TELESCOPE SPECIFICATIONS CALCULATOR

Fill in the white boxes then click the CALCULATE button to see results.
TELESCOPE CALCULATIONS
Objective Diameter:
inches
mm
         Minimum Recommended Eyepiece: mm
 
f/ ratio ratio          Maximum Recommended Eyepiece: mm
 
Focal Lenth:
inches
mm
         Planet etc., Recommended Eyepiece: mm
 
Your Eye's Entrance Pupil*: mm          Dawes Limit Smallest Resolvable Angle: seconds of arc
 
Limiting Magnitude:
 
Aperture Gain Light Gathering Power:
x the human eye
 
Minimum useful magnification x
 
Maximum useful magnification x
 
Best Mag for Planets, Messier objects, general viewing x
* This measurement refers to the opening diameter of your pupil in which light must enter. This is not the same as the exit pupil. The term "exit pupil" better refers to the amount of light exiting the eyepiece and the term "entrance pupil" refers to amount of light capable of entering your eye via the pupil. (Reference Source)
Click this link to determine your own Entrance Pupil diameter.


EYEPIECE CALCULATIONS
    Eyepiece
Size
       Resulting
Magnification
       Eyepiece
Field
of View
       True
Field
of View
       Telescope
Exit
Pupil
       Field transit
time at 0
declination
       Minimum
Resolution
of Lunar
Features
       Minimum
Resolution
of Lunar
Features
   
  mm   x   °   °   mm   sec.   km   mi  
 
Simply enter new eyepiece criteria and click this CALCULATE button
without reentering the telescope data above, to see new eyepiece specifications.






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