Big thank you to everybody who's replied so far:

Boni - I love the Atmospheric Sensing Platform, it gave me a good laugh!  :D  Haven't had time to check out the other links properly. And I think that including Poser DoF stuff here too is a good idea - other people may prefer it to postwork DoF.

hborre - nice concise explanation of the bright white bits in the renders I posted - thank you! That made the bit on p139 of the manual that I quoted click.

cedarwolf - great to know that I'm not going to be the only one getting something out of this thread.

aRtBee - your tutorials on other Poser stuff have helped me get to grips with things in the past. I'll be checking your atmosphere ones later today. many thanks!

bagginsbill - I tried a very similar search yesterday and got nothing, even with Google (posted on the Community Center forum about the problem). Looks like it's working today - your link is like a gold mine! :)

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The 3Dcheapskate (also available in DAZ and HiveWire3D flavours) occasionally posts sensible stuff. Usually by accident.
And it usually uses Poser 11, with units set to inches. Except when it's using Poser 6 or PP2014, or when its units are set to PNU.