Quote:
Originally Posted by AstroStudentUSQ
https://www.bintel.com.au/product/or...ide-eyepieces/
20mm Eye relief and 30mm lens diameter for the Orions.
Wavytone, have you noticed any CA in the outer 10% or so of those Vixens? I did read one review that mentioned this, keen to hear of users views on them as this is one of the brands I am closely looking at.
Cheers,
Mark
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80° requires a minimum of 33.6mm of eye lens diameter for 20mm of eye relief
30mm of eye lens diameter and 20mm of eye relief means a maximum of 73.7° apparent field.
If these eyepieces do indeed have an apparent field of 80° then the eye relief is really 17.9mm. That's still pretty long for an 80° eyepiece.
If you want to work the math for yourself:
tan0.5ApparentField = 0.5lens diameter / eye relief
One adjustment to that: the depth of the concavity of the eye lens is added to the eye relief so calculated. If the LHD has an eye lens that is 1mm concave, then eye relief could be 18.9mm.
If the eye lens is convex, the convexity amount is subtracted from the calculated eye relief.