Venus and Medusa at Prime

One thing I really liked about old, manual focus lenses is that when you set the lenses on Infinity = ∞ you got ∞ = Infinity. That is not the case with modern, auto-focus lenses. Often when I set my auto-focus lenses to manual focus, and then turn the focusing ring until the indicator is on ∞, and point my camera at the stars, which are infinitely far from the focal plane on my camera, the infinity at ∞ I have manually set the focus to is not the same infinity as the stars, and the photos are slightly out of focus. If the photo matters (not all photos matter), then I will make sure that I get the right infinity, so the image is in focus, but general fly-by-night photos like these that I took at Prime, Vespers and Compline, I set the lenses to infinity and they focused somewhere either short of or beyond infinity.

Orion's belt and saucers at Vespers

Moon, clouds and contrails at Compline.