I had heard of the Televue Dioptrx and read some reviews, but none really grabbed me with a "you gotta try this!" message.
As a result of a low-ball bid on eBay, I recently had the opportunity to try one. By simply holding it over the eyepiece while observing the Veil Nebula. I rotated the Dioptrx and was very pleased to see the flared stars become pinpoints across the field of view of the 31mm Nagler.
However, I also noticed that the contrast of the Veil improved as well. Thinking I might be imagining things, I moved the Dioptrix in and out of the light path. The nebula definitely appeared more prominent across the entire field with the Dioptrix in place.
Has anyone else experienced this?