My previous drawing of 1880s Jupiter was a hybrid of various late 19th century depictions of the planet. But the fact that it didn't really depict Jupiter as it ever actually looked was bugging me, so I decided to do a study on one of the drawings I used as reference for the previous drawing: Trouvelot's drawing of a double moon/shadow transit on Jupiter on November 1st 1880.

This is a pastel illustration from Étienne Trouvelot's 1882 book The Trouvelot Astronomical Drawings, based on observations he made with the 26" Great Refractor at the U.S. Naval Observatory in 1880.

In my astronomy circles this is a notorious image for how exaggerated and cartoony its features are. I think that's what really drew me to this image in particular. There's so much detail here... but none of it looks at all realistic. So what did it really look like that would have led to the very... creative depiction by Trouvelot?

I used Stellarium desktop to get an accurate view of Jupiter at the proper time. (You can barely make out the date on the scanned drawing. I can't read the time, so I set Stellarium to the time that most closely matched the drawing.)

This gave me the lighting angle (slightly gibbous on the antispinward limb), tilt of the bands (bowed down towards the south), and the accurate positions and sizes of the satellites and their shadows. I did not use the texture as reference.

I usually start by getting the shading right before moving on to surface features. In this case there was limb darkening all around, but a little darker on the antispinward side.

Then I started to work on the features, using mostly Trouvelot's drawing but also some modern imagery for reference on the finer details.

The black beads on Trouvelot's drawing correspond to the latitudes where we see elongated oval 'brown barges,' a type of storm found largely in the northern hemisphere of Jupiter. The billowing clouds on the equator look like an exaggerated view of the arching swirling festoons sometimes visible on the equatorial zone. The dark North & South Equatorial Belts were interpreted as both being partly covered by white cloud layers, in order to result in the particular banding pattern seen in the drawing. The scale of the Red Spot was taken from photos and sketches of around the same time which were not quite so exaggerated.

Here's some variants on the final image:

Here it is in the traditional north = up view.

This one is a zoomed out view which also shows Ganymede & Callisto

And this one is a simulation of what Trouvelot's view that night actually might have looked like. I assume perfect seeing conditions (in reality there would be more turbulence in Earth's atmosphere than depicted here, but this is a sort of best case scenario). A 26" f/15 refractor would actually have quite a lot of chromatic aberration, so I simulated that, and added a yellow filter both to match the drawing and to cut the C.A. a bit.

If you look at the simulation in fullscreen, it would be at (very roughly) the same image scale as what Trouvelot may have seen.

The same view zoomed in so you don't have to go fullscreen.

And finally, a faux photograph version:

Here are two early photographs of Jupiter. The earliest one, c, is from September 1879 taken by A. A. Common in London. Early photographic film was sensitive only to blue-violet light, so we can imagine that c is the blue channel only of a hypothetical color image. Photo d is from October 1890 seen by the Lick Observatory in California with a yellow filter.

Just to get a vague idea of what we're working with, I made an unholy abomination by using the Common photo as the blue channel and the Lick photo as the green and red channel. (Many of the color photos of Jupiter from the Voyager space missions used an orange filter as the green and red channel and a violet filter as a blue channel; this is the same concept at least on a color theory level.)

This was my result--the implication is that like in the late 1970s and early 2020s, Jupiter's normally pale equatorial zone was a rich orange color.

Of course, the two images are 11 years apart and a lot can change in that time, but the basic takeaway is that the dark blue equatorial zone is probably best explained by an orange-red coloration, rather than the equatorial belts having moved over time.

These drawings were also used as reference. b, a very cartoonishly exaggerated drawing, was made by Étienne Trouvelot on 1880 November 1 at around 9:00 EST and depicts a double transit of both Io and Europa as well as their shadows across the face of Jupiter.

c, a much more modest and accurate sketch, was drawn by Thomas Elger in November 1881. It was from Elger's sketch that I took the proportions of the Great Red Spot.

I also used this sketch of mine from August 2021 as a reference for the orange coloration, since the colors used in this digitally colored pencil sketch were chosen to match the true colors I was seeing in the eyepiece of my 10" reflector telescope. Note how much smaller the Great Red Spot was in 2021 than in the 1880s.

The features are primarily a hybrid of Trouvelot and Elger's renditions of the planet. For fine detailing I used various modern sources such as Hubble Space Telescope, Voyager, and Cassini imagery of Jupiter.

The end result is a hybrid of many sources, and not an accurate depiction of any one moment in the 1880s-1890s period. However, the position of Jupiter's moons and their shadows represent a moment on the evening of November 1st, 1880, a few hours after Trouvelot's drawing was produced.

Astrophotos are usually shown inverted to match the view through an eyepiece. That's why the GRS was on the top of all of the above images. However, my drawing uses north = up to bring it into line with modern depictions of Jupiter.

This zoomed out view shows Europa as well as Io. The shadow on Jupiter belongs to Europa. Note that this view is from a random point in space near Jupiter, not from the Earth. Fun fact: Two of Jupiter's small asteroid sized moons are visible in this image as well. Can you spot them?

Here is a version cropped to 4:3 and with the shadow removed.

Here's a fictional 1880s style black & white photo, perhaps taken from the window of a steampunk space ship. To simulate the sensitivity of film to blue-violet light, I used just the blue channel of the image to produce this photo.