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Eyepiece Calculator
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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: 2,700.0mm
Aperture: 180.0mm
Focal Ratio: 15.0
Include 2-inch data: True
Table corrected for Paracorr: False
List only DIOPTRX eyepieces: False
Max recommended mag. for aperture: 350x

d:180mm, f:2700mm, w/2in
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)
 Panoptic  41  68  27  2"  65.9  2.7  0.98  51.1  --  131.7  --  --  263.4  -- 
 Nagler 5  31  82  19  2"  87.1  2.1  0.89  46.7  --  174.2  --  --  348.4  -- 
 Panoptic  35  68  24  2"  77.1  2.3  0.82  43.0  --  154.3  --  --  308.6  -- 
 Nagler 4  22  82  19  2"  122.7  1.5  0.66  34.6  --  245.5  --  --  490.9  -- 
 Panoptic  27  68  19  2"  100.0  1.8  0.65  33.9  --  200.0  --  --  400.0  -- 
 Panoptic  24  68  15  1¼"  112.5  1.6  0.57  30.0  225.0  225.0  281.3  337.5  450.0  562.5 
 Nagler 4  17  82  17  2"  158.8  1.1  0.52  27.0  --  317.6  --  --  635.3  -- 
 Nagler 5  16  82  10  1¼"  168.8  1.1  0.47  24.6  337.5  337.5  421.9  506.3  675.0  843.8 
 Panoptic  19  68  13  1¼"  142.1  1.3  0.45  23.7  284.2  284.2  355.3  426.3  568.4  710.5 
 Delos  17.3  72  20  1¼"  156.1  1.2  0.45  23.6  312.1  312.1  390.2  468.2  624.3  780.3 
 Nagler 6  13  82  12  1¼"  207.7  0.87  0.37  19.6  415.4  415.4  519.2  623.1  830.8  1,038.5 
 Delos  14  72  20  1¼"  192.9  0.93  0.37  19.2  385.7  385.7  482.1  578.6  771.4  964.3 
 Delos  12  72  20  1¼"  225.0  0.80  0.32  16.7  450.0  450.0  562.5  675.0  900.0  1,125.0 
 Delos  10  72  20  1¼"  270.0  0.67  0.27  14.1  540.0  540.0  675.0  810.0  1,080.0  1,350.0 
 Nagler 6  9  82  12  1¼"  300.0  0.60  0.26  13.8  600.0  600.0  750.0  900.0  1,200.0  1,500.0 
 Delos  8  72  20  1¼"  337.5  0.53  0.21  11.0  675.0  675.0  843.8  1,012.5  1,350.0  1,687.5 
 Nagler 6  7  82  12  1¼"  385.7  0.47  0.21  10.8  771.4  771.4  964.3  1,157.1  1,542.9  1,928.6 
 Delos  6  72  20  1¼"  450.0  0.40  0.16  8.4  900.0  900.0  1,125.0  1,350.0  1,800.0  2,250.0 
 Nagler 6  5  82  12  1¼"  540.0  0.33*  0.15  7.8  1,080.0  1,080.0  1,350.0  1,620.0  2,160.0  2,700.0 
 Delos  4.5  72  20  1¼"  600.0  0.30*  0.12  6.2  1,200.0  1,200.0  1,500.0  1,800.0  2,400.0  3,000.0 
 Nagler Zoom  6 - 3  50  10  1¼"  450.0 - 900.0  0.40 - 0.20*  0.11 - 0.06  5.7 - 2.9  900.0 - 1,800.0  900.0 - 1,800.0  1,125.0 - 2,250.0  1,350.0 - 2,700.0  1,800.0 - 3,600.0  2,250.0 - 4,500.0 
 Nagler 6  3.5  82  12  1¼"  771.4  0.23*  0.10  5.3  1,542.9  1,542.9  1,928.6  2,314.3  3,085.7  3,857.1 
 Delos  3.5  72  20  1¼"  771.4  0.23*  0.09  4.9  1,542.9  1,542.9  1,928.6  2,314.3  3,085.7  3,857.1 
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.

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