If you want to know how an eyepiece manages light, look at the moon and sweep off to the side also.
I had an eyepiece, 5mm FL, that had a huge flare of light at certain positions pointed at the moon. It was very annoying and made looking at the moon difficult at certain orientations.
Tried everything - flocking the tube, additional stops inside the tube...
Finally, what worked was to flock the retaining ring of the forward Smyth lens and the barrel area just after the retaining ring.
That worked well. Plus, in order to avoid any vignetting caused by the addition of the flocking material, I used Edmund Optics flocking, which a group of us found to be the thinnest available. No light reduction was noticed except for the flaring.
But sometimes glare and reflections take some investigating to figure out where the issue is.