I've been reading though pages in this wiki and it seems that there are some disrepancies regarding Astro Lairs/Caves whatever you call them. At first I took it for granted that "Cave Frequency" changes how many Astro Lairs will spawn, and many wiki pages say so, but I've also read that "Cave Fequency has nothing to do with Astro Lairs, but rather the now-obsolete chasms or something that was intended to be eventually added to the game (likeoxygen levels , for example).
Now I've got a few worlds. My main one, (40km^2 -- but I also got lost a lot without finding any astro lairs, which fustrated me coz I wanted to get killed so I could spawn back home.... so I'd estimate that the area I "know" is about 25km^2) has now more than like 15 Astro Lairs (can't be bothered to count them at the moment).
I always put Cave Freq to maximum but in other worlds there aren't that many astro lairs. The problem is I also fiddle with the plant cover, wildlife, etc options so I can't draw to any reliable conclusions.
So, to make the Wiki reliable, should we make a total clean up of all Astro-Lair spawning guesses, and actually state them to be possibilities which we aren't at present sure about???
On the side I'd like to add that recently I commented that I supported Origami Dragon's theory that Astronauts can spawn anywhere.
In my travels, while the renderblocks were lagging but I could see the wildlife ahead, I realised that many of the wildlife were underground (not any space giraffes or green mobs tho), and, using the transperency glitch I could see that the mobs were moving up and down through blocks (though not side to side).
Therefore I concluded that Astronauts that can be found in underground astro lairs get there by glitching downwards though solid blocks. After all it is a well know fact that they spawn with their legs in the ground.