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Telescope Calculator
Measure the performance of your telescope and experiment with new eyepieces and accessories.
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Solar System
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Telescope aperture
mm
Telescope focal ratio
Eyepiece focal length
mm
Eyepiece apparent field
30 degrees
35 degrees
40 degrees
42 degrees
45 degrees
50 degrees
52 degrees
55 degrees
57 degrees
60 degrees
65 degrees
66 degrees
70 degrees
75 degrees
80 degrees
82 degrees
90 degrees
100 degrees
Barlowlens
None
1.5 x
2.0 x
2.5 x
2.8 x
3.0 x
3.5 x
4.0 x
4.5 x
5.0 x
Focal Reducer
None
0.2 x
0.3 x
0.4 x
0.5 x
0.6 x
0.7 x
0.8 x