colossus 129 last couple of questions

What words intersect with your e-e-r "clear sky"? (and the clues for these?)

Clear sky might be ether.

278d = RANCH
297a = ETHER

That should do it!

I did think of that, but since I am familiar with the word from 19th century physics theories which supposed that electromagnetic radiation (radio waves, light, etc) required a medium through which to travel, the so-called "luminiferous ether", which was thought to pervade all of space. For 100 years ago this has been considered obsolete. I rejected it as being an inaccurate word for the sky, clear or otherwise. What you mainly see at night when the sky is clear is the moon, stars and sometimes planets. Are we to suppose that the puzzle setter meant that the dark bits in between these things? It has the air of being a hasty last-minute clue.