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Message: <blockquote data-quote="henry link" data-source="post: 1610895" data-attributes="member: 6806">Holger Merlitz' graphic shows very well how this kind of internal reflection can be invisible in bright light, but obvious in dim light. Other variables in its visibility are caused  by such things as the unavoidable constant pupil misalignment when hand holding which brings the reflection into view intermittently and by the preferred eyecup position of different users. If a user tends to rest the eyecups up on the brow the reflection will be more obvious than resting the eyecups down on the cheek.As Holger suggests there is only one real cure for an internal reflection like this and that is to baffle it at the source. The eyepiece fieldstop does not make a good baffle for a reflection at the edge of the objective or the focusing lens because it's too far away from the source. The baffle needs to be just behind the reflection. Then the problem is solved for everyone under all conditions at virtually no cost.</blockquote>