The human eye has a cycle time of roughly 1/20 second. That is why movies are projected at 24 frames per second and TV at 30 frames per second. In other words, clear vision does not persist for more than 1/20 second. After that, the cells in the eyes are reset and previous information is deleted.

Chemical photographic films quickly replaced the human eye in telescopes as soon as they became sensitive enough because they could collect light for hours instead of only a fraction of a second. A crystal of silver halide can retain quantum activation for months, or even years.

Electronic photography has supplanted chemical photography in astronomy because of greater sensitivity.

If you have ever looked through a REAL professional telescope, you will have been surprised to discover that, although point sources such as stars are much brighter, diffuse sources, such as planets and nebula are no brighter through the telescope than to the naked eye. Larger, yes; brighter, no.

This is due to the famous Liouville Theorem applied to geometrical optics. No amount of clever optics will ever circumvent the physical limitations and permit you to see the beautiful nebulae displayed in pictures from the Hubble or other modern telesopes, since these pictures were taken by detectors with vastly longer collection times than the human eye.

David F Mayer