Eyepiece Calculator
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The eyepiece calculator reveals the observing potential of your telescope with Tele Vue Optics eyepieces. It accepts basic information about your telescope and displays results for all current Tele Vue eyepieces. Refer to the diagram and tables below for the definition of the input and output parameters.

Input Box
Follow the steps below to see the eyepiece table.
(1) Enter any 2 of the 3 parameters for your telescope
You must enter 2 telescope parameters to see table results.
(2a) Choose telescope eyepiece preferences
(2b) Limit to these eyepieces
(3) Enter optional title 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
Formulas

Note on Field Stop Data
For discontinued or currently unavailable eyepieces, field stop data can be found in Eyepiece Specification table.

Definitions

apparent field: perceived span of sky seen through eyepiece (without telescope). Not used in true field (see) calculation.
exit pupil: image of objective formed by eyepiece. Location where full apparent field is seen.
f/#: a ratio that describes the relation between the aperture and focal length of the telescope -- important for photography
field stop: ring inside the eyepiece barrel that limits true and apparent field size
focal length: effective distance from entrance of an optical system to focal point
magnification: relative change in angular size of object
true field: span of sky seen through telescope/eyepiece combination


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