Double-checking something I read about using high ISOs for astrophotography

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Ellis Vener
Ellis Vener Forum Pro • Posts: 15,587
Double-checking something I read about using high ISOs for astrophotography

While doing some research on another topic I came across the following:

"The amplification process also means that any noise will be amplified too, and that is why we see more noise at higher ISOs as we shorten exposure time to fit in the smaller digitization range. But at the same time, noise from camera electronics decreases relative to the subject being photographed. So the bottom line is the higher ISO decreases true exposure for metered scenes, recording less light, and amplified the smaller signal to compensate but camera electronics noise improves with no simple rule on which ISO is better. But if we kept exposure time and f-stop fixed and raised ISO to brighten the image, as one might do in night Milky Way or aurora photography, noise will decrease as ISO is increased. Another example: indoor low light photography: fixed f-stop for depth of field, fixed exposure time to minimize subject movement, then raising ISO will not increase noise nor change how much light is collected."

(Source: https://clarkvision.com/articles/iso/)
If I am reading this correctly, does this mean there is less need for very fast primes for astrophotography than many people think? In other words, might a f/2.8 lens be just fine  for general astrophotography + landscape purposes as opposed to thinking I need to also purchase a larger aperture lens of the same focal length? I  do understand that more light in a shorter time is generally better for "freezing" motion but if using a higher ISO for this purpose works just as well is there a real need for spending more money?

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Ellis Vener
A working photographer since 1984.
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