Having a technical basis for the system with a predictor should prove very useful. You didn't mention if the two stars had the same spectral output. We had another thread not so long back for what happens with creatures who can see outside of human visible spectrum. This might add more flavor into the mix when certain creatures come out or hibernate depending on which star is out.

http://www.cartographersguild.com/showthread.php?t=3319

We also had another thread talking about eclipses too. With a binary and two asteroids you must have them frequently. Perhaps with an 80yr orbit those eclipses could last longer than ours and a 10hr asteroid might have quite sudden light dropping eclipse effects lasting mere seconds...

If the seconds star at mag -20 is out by itself then presumably you would be able to see that asteroid as a dark shape going across the sky.