The wiki for sky:

Use this tag if the sky is used as a focal point or the actual subject.

Would this prevent starry sky from implicating it? i.e.

create implication starry_sky -> sky

Edit:
Reason: [adjective] : [noun] relationship
Additionally,both emphasise a focus of the sky

I've always been under the impression that sky is used when the sky is visible in the image, focal point or not.

EB said:
I've always been under the impression that sky is used when the sky is visible in the image, focal point or not.

This is how I've always tagged it too.

However, I've never been sure if blue sky should be tagged when blue can be seen in the sky (to indicate it was daytime, as opposed to black or red) or whether it means clear sky, where no clouds are visible (maybe some mist near the horizon, which is a different phenomenon).

I tag sky when it's a focal point or at least noticeable; a quick glance at sky shows the majority tags it that way as well, aside from a handful of outliers.

As for the implication itself, most of the starry_sky posts also have a focus on the sky itself. The implication is probably sound.

What you all said seems to makes sense, for both sky & starry_sky the focal point would've been the latter in any case

Updated the OP

Did
create implication starry_sky -> sky