In an article by Starizona they suggest completely the opposite: "A smaller aperture telescope will tolerate more power per inch than a larger instrument."
Here is a link to the article:
So, they suggest that a larger 8" telescope will be normally used at a 30x per inch = 240 for maximum quality of the resulting visual image.
There is a lot going on here. Like everything else related to observing, there are few hard and fast rules because there are many variables. Seeing, object type, observer acuity to name a few. Optical quality always finds its way into the conversation, too.
Image breakdown seems to happen at two or three points on the magnification scale. Once where seeing becomes objectionable to our preference for a steady image. Next when aberration or obstruction effects become visible, and lastly when the (object type) becomes too dim to see well at small exit pupils.
In my 8", I'm at 400x easily enough on Jove as the standard extended object. Non point source, extended bright low contrast detail is about max for me.
From the article. "This works out such that the image through a telescope can never be brighter than the image as seen with the unaided eye."
An interesting thought experiment with exit pupil is imagine you have a 6" scope operating at 1mm exit pupil and 150x. Point your scope at a small faint galaxy you can see.
Now, drop in an eyepeice that gives 1x and a 150mm exit pupil. Imagine further your iris can open to an impossible 6" to accept the light from the exit pupil. Now look up at that galaxy with your naked eye 150mm iris. The view through the telescope and your eye are the same. You don't even need a 6" telescope with a 6" iris opening. (Actually the telescope image is a little dimmer due to transmission loss).
But, if you looked at that galaxy through the telescope at 1x with a 7mm iris, you would not see it in the same way you can't see it naked eye. Not because its not bright enough, but because its not big enough like it was at 150x and 1mm exit pupil. You need a telescope to magnify an object because its not any brighter than it is to the naked eye. Of course, you need light grasp to magnify the galaxy so it retains the same surface brightness at larger image scales. That's why we select exit pupils to pass the light grasp of the scope into our more normal iris apertures.
Telescopes do not make images brighter than they really are, telescopes magnify objects. The result of magnification is the exit pupil. Or, said differently, magnification is the ratio of entrance pupil (aperture) to the exit pupil.
(Had to rush my reply...)
Edited by Asbytec, 26 June 2020 - 11:01 AM.