Hi guys, sorry to bug you with another question about this.
Logically, it seems that magnification works by reducing the field of view angle, so that you're looking at a smaller part of the sky. Now, does this smaller view of the sky get projected over your entire vision? Or is it just enough to fill the exit pupil?
I guess what I mean to say is, since the size of the exit pupil is equal to the aperture divided by the magnification, then the higher the power, the lower the exit pupil for any given aperture. Now, one thing I've noticed, using my tiny 70mm refractor (350mm focal length), is that the image of Saturn with the 6mm eyepiece PLUS 2x Barlow is not that much larger than the image of Saturn with just a 25mm eyepiece. You'd think that, since the former is 116x and the latter is 14x, it seems like Saturn should be more than 8 times larger in the former case, but this is not my experience.
I'm wondering if this is because of the exit pupil. At 116x the size of my exit pupil is about 0.6mm, whereas at 14x it is about 5mm. I'm wondering if the reason that Saturn doesn't look much larger is that, at 116x, the image is magnified at over 8 times the 14x, but that image is displayed on a pupil that is about 8 times smaller.
And I guess that, if this is true, a corralary to it would be that increasing the aperture without increasing the magnification would result in an increase in the exit pupil size, and therefore, an increase in apparent size of the objects being viewed.
I guess that doesn't make sense.
Edit: In other words, I guess what I'm asking is, does a larger exit pupil, given the same magnification, show a wider piece of the sky? Or does it show the same piece of the sky stretched across a wider area? I guess the former would have to be true, or there would be no point to magnification, because it seem that the math works out such that, as magnification increases, all objects increase in size to the same proportion that the exit pupil decreases in size. So, if the latter were true, there would be no point to magnification at all.