> "How do I use bits to represent concepts in the problem domain?" is the fundamental, original problem of computer science.

> It is, however, about concepts like binary place-value arithmetic

That is the original problem of using a particular digital machine architecture. One shouldn't confuse the practical/instrumental problems at the time with the field proper. There's nothing special about bits per se. They're an implementation detail. We might study them for practical reasons, we may study the limits of what can be represented by or computed using binary encodings, or efficient ways to do so or whatever, but that's not the central concern of computer science.

> In second year university I learned computer organization more or less in parallel with assembly.

Sure. But just because a CS major learns these things doesn't make it computer science per se. It's interesting to learn, sure, and has practical utility, but particular computer architectures are not the domain of computer science. They're the domain of computer engineering.

> The astronomer is, however, studying light.

No, physicists studying optics study light in this capacity. Astronomers know about light, because knowledge of light is useful for things like computing interstellar distances or determining the composition of stellar objects or for calculating the rate of expansion or whatever. The same goes for knowledge of lenses and telescopes: they learn about them so they can use them, but they don't study them.