Since John Herschel was first to make a photograph on a glass plate in 1839, why was the first astronomical photograph not taken until 1840 by Draper?

Question

Researching Who named "the 37 cluster" or at least made that name widely known via writing? I came across the Moneylink September, 9, 2020 article 9 September 1839: Sir John Herschel takes the first glass-plate photograph

Frenchman Louis Daguerre is famous for inventing the daguerreotype – an early form of photography that used metal plates – in 1839. But on 9 September of that same year, our own Sir John Herschel created a photographic negative on a glass plate, using silver chloride. It is he who introduced the word “photography” into the English language.

Herschel was one of the great Victorian polymaths, happy to turn his hand at almost anything. Besides his pioneering work in photography, he excelled at botany, maths, chemistry and the family hobby: astronomy. His father was Sir William Herschel, after whom the space observatory, which blasted off in 2009, is named.

The photograph is of William Herschel's telescope. So there's the photographic plate and a nice big telescope (oops, there's no telescope held within the iconic structure in this photograph), one looking at the other. And yet, the first astronomical photographic image didn't happen until the next year.

From this answer to First photographic image taken with telescopes to produce astronomically useful results? What telescope was used?:

The first astronomical photo was of the moon, taken by John Draper in 1840, using the daguerreotype process itself.

(side note, Wikipedia's John William Draper says:

In March 1840 Draper became the second person to produce photographs of an astronomical object, the Moon, considered the first astrophotographs.¹⁵

¹⁵ Kalfus, Skye (2010). "Across the Spectrum". Chemical Heritage Magazine. 28 (2). Chemical Heritage Foundation. Retrieved 23 March 2018.

Question: Since John Herschel was first to make a photograph on a glass plate in 1839 (and it was of an astronomical telescope!), why was the first astronomical photograph not taken until 1840, not with a glass plate (daguerreotypes used copper substrates), and instead by John Draper?

Herschel's 1839 photo of his father's telescope in Slough (Getty)

Answer 1

One possible answer is that Herschel probably understood that the state of the art in photography in 1839-1840 wasn't astronomically useful. If you look at Draper's photograph of the Moon, it's pretty limited in detail. It's basically an uninformative -- if cool -- stunt: you probably wouldn't learn anything new about the Moon from it.

People had been sketching the Moon as seen through telescopes for over two hundred years. There was no general perception that the surface of the Moon was at all variable (aside from the changing phases), so a careful drawing by a competent artist was useful at all times, and probably far more useful than what could be obtained from the photographic technology of the time.

The Sun makes for an instructive contrast. It is, of course very bright, so you can feasibly take photographs of it with 1840s technology in a short period of time (1/60 second!), without having to worry about tracking it. Moreover, it has sunspots, which come and go and move around, so that a (primitive) photograph of the Sun at a particular moment (potentially) has astronomically unique and useful information that a photograph of the Moon would not. It's maybe relevant that the first serious celestial photographs were in fact of the Sun, starting in 1845, and the first photograph of a solar eclipse was in 1851.

So I would guess that Herschel assumed (correctly) that there was nothing (astronomical) to be gained by trying to photograph the Moon in 1839 or 1840, compared with observing it using the much more sensitive dark-adapted human eye. He may have known about Louis Daguerre's failed attempt to photograph the Moon in 1839, which apparently produced only a featureless blur. (And I get the impression that Herschel's interest in photography was a very general one, based in part on his longstanding interest in chemistry, and not something connected with his interest in astronomy.)

The first-known attempt at astronomical photography was by Louis Jacques Mandé Daguerre, inventor of the daguerreotype process which bears his name, who attempted in 1839 to photograph the Moon. Tracking errors in guiding the telescope during the long exposure meant the photograph came out as an indistinct fuzzy spot.

Answer 2

John Herschel took a photo in September and Draper took one the following March. That's only a 6-month interval at a time when photography didn't exist. You're asking why Herschel didn't think of doing everything at once. There is no problem here.

On top of that, John Herschel who took the 1939 photo was a different person than William Herschel, the famous astronomer who discovered Uranus. John's early interest was photography and math, not astronomy.

William Herschel did very important things, but inventing astrophotography wasn't one of them.