Used the resonator to find the best spot, however, the table does not gather enough starlinght

From a better perspective

Seems like you forgot that the height/y-position of the altar matters aswell. ;)

I personally think this is a problem. You will hardly find a "blue" position in the right y-level (what will that be ? y=100? y=150?), especially in older bioms o plenty worlds. That means you will have to build ridiculously high towers from 60 to 150 (?) only to get enough light for the highest tier of the altar. Suggestion: playable enhancement of the Star-light, perhaps the floating crystals to add them somehow to the Altar to let it i a slightly lower y level. The crystals themself should be buildable in lower levels. Or anything similar.

An option to "avoid" having to find spots with the resonator was/is added next version.
Also, "good spots" are based on x/z coordinates. The y-level doesn't matter for the resonator-spots themselves.
Additionally, if you're to progress into the currently last stage in progression, you can just link a crystal to the altar via the 'starlight network' - so linking tool & optionally lenses and stuff. There will be an additional clarification research-node in the next version mentioning the general philosophy behind the starlight network.

good to know. But doesnt help if the crystal itself needs "too much" starlight (as in my case). My tower is already 40 blocks high... and i have to add at least 20 (?) or so levels. I had to re-buold it already 2 times, for there is now way to tell, if the spot is "good " in terms of y -level for future progression and until now no way to enhance it without building the whole thing higher than before. Suggestion: make the crystal "cheaper" in terms of light (for getting it) and then 2 or more of them with lenses to enhance the altar without re-build the thing every two days.