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. Use browser back button to see prior results.
(1) Enter any 2 of the 3 parameters for your telescope
Focal LengthApertureFocal Ratio (f/#)

(2a) Choose telescope eyepiece preferences
Does your telescope accept 2" eyepieces?
Are you using a Tele Vue Paracorr?
Limit to eyepieces that accept DIOPTRX astigmatism correctors?

(2b) Limit to these eyepieces
 Ethos    Nagler    Panoptic    Delos    Plössl
You must choose at least one of these to return data.
If you choose none, all will be selected when the calculation returns.

(3) Select table presentation order and enter optional title
Sort Results By:   Title:
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 by low-power specs.

4) Calculate Results  
You must enter 2 telescope parameters
to see table results.

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

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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