I noticed a slight error that seems to be floating around out there on the net. Several “this day in history” sites, including the Wikipedia page on 4 March list today as the “first sighting of Orion Nebula by William Herschel” in 1774. Strictly speaking that’s not untrue—Herschel seems to have made his first observations of the Orion Nebula on 4 March 1774, but in fact, telescope observations of the nebula had originally been described by Peiresc back in 1610 (cf. a lengthy list of early observations of deep-sky objects).
What’s important about Herschel observing Orion is that it got him started on a massive cataloging campaign that resulted in a list of thousands of deep-sky objects. And a numbering system that’s still in use today!
All this thinking about the Orion Nebula reminded me of the image shown above—a sketch by William Herschel’s son John. I link to a fine-art print offered by David Malin of the same, and in a continuing cascade of connections, I also wanted to point out a marvellous essay by Malin in which he compares Herschel the Younger’s drawing to (a somewhat more psychedelic) one created by William Parsons. As he points out, differences between the two images “result not from changes in the nebula or in telescopic power, but from subjective differences in the way their creators saw, remembered, and sketched what was essentially the same subject.” I’ve blogged about related issues before, but Mailin is both nicer and more eloquent than I.
Anyway, I hope you appreciate a random stroll down this-day-in-history lane.