Dick: Yes, you beat me to the response.

Roger: if you're talking about color images, you absolutely must distinguish between bits-total vs. bits-per-channel. 24-bit color is 8 bits per channel (as RGB), barely adequate for final presentation (esp. for high dynamic range images as astrophotos usually are). Again, 8 or 10 bits *per channel* will prove utterly inadequate for intermediate processing. Just use floating point numbers for your image processing. PixInsight always does, if memory serves.

What numerical format and depth you use in the final image rendering is a completely different subject. 8 bits per color channel has been standard monitor presentation for some years, as Dick notes. But 8 bits per channel won't suffice for very high pixel counts (because the human eye is very, very good at detecting edge artifacts in smooth gradients, which is why dithering was a popular "remedy" in digital imaging's early days). And 8 bits per channel sure won't be enough to represent astrophotos, very marginal even if HDR processing is in play.

As for Apple's "10 bit", I assume with Dick that it probably means 30 bits total (RGB).

If you see "16-bit color", that almost always means a subset of the colors available in "24-bit color". If you see "32-bit color", it almost always means 8 bits per channel, the 4th channel being "alpha" (opacity), often useful for image processing (layering), but not for final presentation where (by convention) alpha is exactly one.

Color and image processing don't have to be a rabbit hole. It can be learned. But first, the terminology must be mastered, else all is confusion. I hope our comments help a "bit".