>What does it look like in the daytime?

It's far enough away that I can't see it. I can only see the light—which, now that I think about it, puts it farther away than the two antennas in the Pelham–Belchertown hills are from Rt. 116 (at that stretch, South Pleasant Street) in Amherst. (They're visible over Amherst College's wildlife sanctuary's meadow.) The northern one is a cell tower near the intersection of Amherst Road and Rt. 202 in Pelham, while the southern one is WFCR's transmitter (as well as that of WAMH at Amherst college).

>There's a radome on a hilltop on the UMass campus that you might be pointed to at times, though that's not really very far above terrain.

I believe you're thinking of the observatory on the rise/ridge between Orchard Hill and Sylvan (PDF).

>But there's also a north/south run of power lines with towers that are tall enough they might require lighting at night.

I've paralleled them on Rt. 116 and crossed under them on east–west roads and never seen a light.

>WHYN's towers rise in a field in Southampton but that doesn't seem to be the direction you're looking in or necessarily even visible given intervening ridges.

That's very true. The view is directly west and very constricted by the trees lining the road.