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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: 1,656.0mm
Aperture: 360.0mm
Focal Ratio: 4.6
Include 2-inch data: True
Table corrected for Paracorr: False
List only DIOPTRX eyepieces: False
Max recommended mag. for aperture: 350x

d:360mm, f/4.6, 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"  40.4  8.9*  1.6  83.3  --  80.8  --  --  161.6  -- 
 Plössl  55  50  38  2"  30.1  12.0*  1.6  83.3  --  60.2  --  --  120.4  -- 
 Nagler 5  31  82  19  2"  53.4  6.7  1.5  76.1  --  106.8  --  --  213.7  -- 
 Panoptic  35  68  24  2"  47.3  7.6*  1.3  70.1  --  94.6  --  --  189.3  -- 
 Nagler 4  22  82  19  2"  75.3  4.8  1.1  56.3  --  150.5  --  --  301.1  -- 
 Panoptic  27  68  19  2"  61.3  5.9  1.1  55.3  --  122.7  --  --  245.3  -- 
 Panoptic  24  68  15  1¼"  69.0  5.2  0.93  48.9  138.0  138.0  172.5  207.0  276.0  345.0 
 Plössl  32  50  22  1¼"  51.8  7.0  0.93  48.9  103.5  103.5  129.4  155.3  207.0  258.8 
 Plössl  40  43  28  1¼"  41.4  8.7*  0.93  48.9  82.8  82.8  103.5  124.2  165.6  207.0 
 Nagler 4  17  82  17  2"  97.4  3.7  0.84  44.0  --  194.8  --  --  389.6  -- 
 Nagler 5  16  82  10  1¼"  103.5  3.5  0.76  40.0  207.0  207.0  258.8  310.5  414.0  517.5 
 Panoptic  19  68  13  1¼"  87.2  4.1  0.74  38.6  174.3  174.3  217.9  261.5  348.6  435.8 
 Delos  17.3  72  20  1¼"  95.7  3.8  0.73  38.4  191.4  191.4  239.3  287.2  382.9  478.6 
 Plössl  25  50  17  1¼"  66.2  5.4  0.73  38.4  132.5  132.5  165.6  198.7  265.0  331.2 
 Nagler 6  13  82  12  1¼"  127.4  2.8  0.61  31.9  254.8  254.8  318.5  382.2  509.5  636.9 
 Delos  14  72  20  1¼"  118.3  3.0  0.60  31.3  236.6  236.6  295.7  354.9  473.1  591.4 
 Plössl  20  50  14  1¼"  82.8  4.3  0.59  31.0  165.6  165.6  207.0  248.4  331.2  414.0 
 Delos  12  72  20  1¼"  138.0  2.6  0.52  27.2  276.0  276.0  345.0  414.0  552.0  690.0 
 Delos  10  72  20  1¼"  165.6  2.2  0.44  23.0  331.2  331.2  414.0  496.8  662.4  828.0 
 Plössl  15  50  10  1¼"  110.4  3.3  0.44  22.8  220.8  220.8  276.0  331.2  441.6  552.0 
 Nagler 6  9  82  12  1¼"  184.0  2.0  0.43  22.5  368.0  368.0  460.0  552.0  736.0  920.0 
 Delos  8  72  20  1¼"  207.0  1.7  0.34  17.9  414.0  414.0  517.5  621.0  828.0  1,035.0 
 Nagler 6  7  82  12  1¼"  236.6  1.5  0.34  17.6  473.1  473.1  591.4  709.7  946.3  1,182.9 
 Plössl  11  50  8  1¼"  150.5  2.4  0.31  16.5  301.1  301.1  376.4  451.6  602.2  752.7 
 Delos  6  72  20  1¼"  276.0  1.3  0.26  13.8  552.0  552.0  690.0  828.0  1,104.0  1,380.0 
 Nagler 6  5  82  12  1¼"  331.2  1.1  0.24  12.7  662.4  662.4  828.0  993.6  1,324.8  1,656.0 
 Plössl  8  50  6  1¼"  207.0  1.7  0.22  11.8  414.0  414.0  517.5  621.0  828.0  1,035.0 
 Delos  4.5  72  20  1¼"  368.0  0.98  0.19  10.1  736.0  736.0  920.0  1,104.0  1,472.0  1,840.0 
 Nagler Zoom  6 - 3  50  10  1¼"  276.0 - 552.0  1.3 - 0.65  0.18 - 0.09  9.2 - 4.7  552.0 - 1,104.0  552.0 - 1,104.0  690.0 - 1,380.0  828.0 - 1,656.0  1,104.0 - 2,208.0  1,380.0 - 2,760.0 
 Nagler 6  3.5  82  12  1¼"  473.1  0.76  0.17  8.7  946.3  946.3  1,182.9  1,419.4  1,892.6  2,365.7 
 Delos  3.5  72  20  1¼"  473.1  0.76  0.15  8.0  946.3  946.3  1,182.9  1,419.4  1,892.6  2,365.7 
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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