[Wavytone]

There is an optical phenomenon called "the cardboard tube illusion", described thus:

"If you look through a cardboard tube with one eye at a bright wall, the portion of the wall viewed through the tube looks much brighter than the wall seen with the naked eye. It is almost as if it was being illuminated with a flashlight. Colour and texture seem to be similarly enhanced."

This could be significant for eyepieces too, and I'm wondering if some of you might like to try an experiment if you have a mix of eyepieces to select from. The idea is this:

Eyepieces with relatively small fields of view will give you a large area of black (the field stop) around the perimeter, similar to the cardboard tube.

If it does actually enhance your perception of the central field of view (the wall in the case of the cardboard tube) it should do the same in a narrow field eyepiece.

So the question is this:

Suppose you take two eyepieces with similar field stops (so they show the same actual field of view) - one with a narrow field of view (say a 25mm Kellner) and widefield one (say my 13mm LVW) will your visual limiting magnitude be the same ?

It's possible the limiting magnitude may be fainter in the narrow field eyepiece. It's also possible they're much the same.I also can't help wondering whether under light-polluted skies it may be more pronounced.

Now to devise a test...