How did single dish (or single receiver) radio telescopes originally generate images? That actually sums up my question nicely: How did single dish (or single receiver) radio telescopes originally generate images? - or at least 2D intensity maps or contour plots.

Early radio telescopes were actually not much more than a Directional Antenna pointing up, connected to a sensitive receiver with various filters, maybe an IF stage or two, but no demodulation. You measured the "noise" signal strength as a function of time on a chart recorder - pen and ink. 

I think there were radio images generated and published well before there were high granularity interferometers and computational correlators. The early ones were contour plots, on 2D plotters - again pen and ink.

How was this done? How did, say, a single dish antenna with a single feed generate radio maps?

edit: It doesn't necessarily have to be a dish antenna - it's the single receiver part I'm interested in.
They scan the object, if you point the dish a a point in the sky as the Earth rotates the dish scans across astronomical objects, then move the dish to point at a slightly different position and let it scan across the object again, and again. After a while you can re-construct an image from the scan lines in a similar way to analogue TV.