Calculator
Eyepiece Calculator
TeleVue.com: Article > Calculator
Input Box
Follow the steps below to see the eyepiece table.
(1) Enter any 2 of the 3 parameters for your telescope
... or Recall a Stored Run
(2a) Choose telescope eyepiece preferences
(2b) Limit to these eyepieces
Current: 
Discontinued: 
(3) Enter optional run name and select table presentation order
True Field: Listed from wide to narrow. Eps with same field sort higher mag first.
Magnification: Listed from low to high. Eps with same mag sort wider field first.
Design: Listed from narrow to wide field designs and zooms last.
Note: Zooms sort based on low-power specification.
(4) Calculate Results
Initial Conditions
Focal Length: 805.0mm
Aperture: 110.0mm
Focal Ratio: 7.3
Include 2-inch data: False
Table corrected for Paracorr: False
List only DIOPTRX eyepieces: False
Max recommended mag. for aperture: 260x

d:110mm, f:805mm
UP

DesignFocal
Length
(mm)
Apparent
Field
(°)
Eye
Rel.
(mm)
Barrel
Size
Mag.
(x)
Exit
Pupil
(mm)
True
Field
(°)
True
Field
@
1000
yards
(feet)
Mag.
w/2x
Barlow
(2x)
Mag.
w/2x
Big Barlow
or
Power-
mate
(2x)
Mag.
w/2.5x
Power-
mate
(2.5x)
Mag.
w/3x
Barlow
(3x)
Mag.
w/4x
Power-
mate
(4x)
Mag.
w/5x
Power-
mate
(5x)
 Plössl  55  50  38  2"  --  --  --  --  --  --  --  --  --  -- 
 Plössl  32  50  22  1¼"  25.2  4.4  1.9  100.6  50.3  --  62.9  75.5  --  125.8 
 Plössl  40  43  28  1¼"  20.1  5.5  1.9  100.6  40.3  --  50.3  60.4  --  100.6 
 Plössl  25  50  17  1¼"  32.2  3.4  1.5  79.0  64.4  --  80.5  96.6  --  161.0 
 Plössl  20  50  14  1¼"  40.3  2.7  1.2  63.7  80.5  --  100.6  120.8  --  201.3 
 Plössl  15  50  10  1¼"  53.7  2.0  0.90  47.0  107.3  --  134.2  161.0  --  268.3 
 Plössl  11  50  8  1¼"  73.2  1.5  0.65  33.9  146.4  --  183.0  219.5  --  365.9 
 Plössl  8  50  6  1¼"  100.6  1.1  0.46  24.2  201.3  --  251.6  301.9  --  503.1 
DesignFocal
Length
(mm)
Apparent
Field
(°)
Eye
Rel.
(mm)
Barrel
Size
Mag.
(x)
Exit
Pupil
(mm)
True
Field
(°)
True
Field
@
1000
yards
(feet)
Mag.
w/2x
Barlow
(2x)
Mag.
w/2x
Big Barlow
or
Power-
mate
(2x)
Mag.
w/2.5x
Power-
mate
(2.5x)
Mag.
w/3x
Barlow
(3x)
Mag.
w/4x
Power-
mate
(4x)
Mag.
w/5x
Power-
mate
(5x)
Table Notes

For further reading, see Eyepieces Advice.

Tele Vue recommends maximum magnification of 60x / inch (2.5x / mm) of telescope aperture and 350x maximum regardless of aperture.
*An exit pupil greater than 7.5-mm may be too big for a telescope with central obstruction (most reflectors). Conversely, small exit pupils may reveal eyesight defects such as floaters. Consider binocular viewing to diminish the effect of an eye having floaters.

Copyright © 2003-2020 Tele Vue Optics, Inc., 32 Elkay Dr, Chester, NY, 10918 · Call for advice: 1-845-469-4551 (9am-5pm ET) · Privacy Policy