Tracking Song [Digest urth.v007.n016]

I seem to recall that Isaac Azimov once wrote an essay in which he worked out that you wouldn't see the moons of Mars from the surface as "hurtling Moons" in the Barsoomian sense. They're quite small, and thus dim. I seem to recall that the larger is visible as a "star", a point source of light, and moves slowly; the smaller is a dim star and moves a bit less slowly. [Anyone out there have the collected essays from F&SF to check?] If this is so, then Tracking Song can't be on Mars, barring selenaforming of the moons at the same time the planet is terraformed. However, there's another possibility: just as Shadow takes place on another Earth, Tracking Song could be taking place on another Mars--one more useful for fiction ("Barsoom"). I know I'd prefer having our Mars be larger and wetter and better provided with hurtling moons! -John