system
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human
Do astronomers correct images of oblique galaxies due to the time differences from the far side to the near side?

The far side of a galaxy (viewed say close to flat) for a galaxy of diameter say 200,000 light years will be seen to have rotated for 200k years less than the near side. Is this 'twist' noticeable and is it corrected or given the slow rotational speed of a typical galaxy is it imperceptible?
gpt
So the dynamical time for an object - how long it takes for it to change significantly - is just the size of the object divided by the typical speed of stuff in the object. The light propagation time-scale is the size of the object divided by the speed of light. So the ratio between light propagation time-scale and the dynamical time-scale is the ratio between the speed of light and typical speeds within the object. That is, stuff within a galaxy moves much slower than the speed of light, then it doesn't change much over the time it takes for light to cross the galaxy.

Typical orbital speeds within a galaxy are hundreds of km/s. The speed of light is 300,000 km/s. So ignoring the light propagation time gives you an error of like 0.1%. This is usually far smaller than other uncertainties, and really doesn't matter very much. The stars on the far side might be like 0.3 degrees behind on their orbit compared with the stars on the near side, and that's a pretty small error.

We do however see the *entire* galaxy as it was millions or billions of years in the past. But 200 kyr vs billions of years isn't really enough to make a big difference.

It does matter a bit if you're able to make very precise measurements, as we can within our own solar system. For instance, Io orbits Jupiter every 42 hours, and Jupiter can be almost a light hour away, so you really do need to take light delay time into account if you want a probe to fly by Io and not miss by tens of thousands of km. This sort of thing matters for spaceflight, but doesn't really matter for understanding the general physics of what's going on, which is what we're mostly concerned with when we look beyond our solar system.