Stellalyra Eyepieces experience

[Louis D]

2 hours ago, Ratlet said:

Kind of related, but SAEP is kidney beaning?  Which is often confused for the effect you get when you have your eye too close to an eyepiece with a long eyerelief?  One is a design issue, the other a user issue?

Correct.  Spherical Aberration of the Exit Pupil (SAEP).  Basically, not all exit rays across the field of view come to a single point above the eye lens.

Read this post of mine to see some nice animations from @Ruud explaining the different shadow types:

SAEP shadows are in the middle of the field, not the edges.  That same thread has some images I've taken showing the extend of SAEP in various mid to long focal length eyepieces.  To get the ring shadow, the camera has to be exactly level and on axis with respect to the eye lens.  Otherwise, you get the classic kidney-bean shadow to one side or the other.

A few even show Chromatic Aberration of the Exit Pupil (CAEP) with rainbows.  CAEP is caused by different wavelengths converging at different distances above the eye lens.  It's often referred to as the "Ring of Fire" effect.  Small, extended objects like Jupiter near the field edge actually split into spatially separated red and blue images in my experience.

[Don Pensack]

Here is an illustrated explanation of SAEP (spherical aberration of the exit pupil):

https://www.handprint.com/ASTRO/ae4.html#SAEP