Halley’s Comet was last spotted by the unaided human eye in 1986, and isn’t estimated to be visible again until 2026. For those who can’t wait another 17 years, the Ransom Center’s exhibition, Other Worlds: Rare Astronomical Works, offers visitors an early glimpse of Halley’s Comet, as rendered by John F. W. Herschel in 1835–1836.
Halley’s Comet was no novelty for Herschel; she discovered no fewer than eight comets in her lifetime. She drew these four illustrations of Halley’s Comet in her late eighties, after being awarded a gold medal and honorary membership from the Royal Astronomical Society. Also on display are pencil sketches of Halley’s Comet by Herschel’s astronomer nephew, John F. W. Herschel, and six illustrations of comets by various other astronomers.
The Ransom Center’s Coronelli Celestial globe (ca. 1688) is almost five feet high and depicts several constellations labeled in Italian and Latin. To coincide with the current exhibition, Other Worlds: Rare Astronomical Works, the technology and digital services department developed a virtual model of the globe for our website. Photographer Pete Smith and technology services graduate intern Ramona Broussard describe how they assembled this model:
The first challenge we encountered in creating this virtual model was moving the globe to the photography studio to capture high-quality images. The Ransom Center’s exhibition preparation department had to remove a door so that the large globe could fit inside the photography studio.
After our first test shots, we realized that the lighting would have to be polarized to clear up the glare coming off the shiny surface of the globe. The final lighting setup required five powerful flash units and numerous reflectors. For the animation to run smoothly, the globe had to be rotated the same distance for each photographed frame. After some investigation we found that the globe was marked with 72 longitudinal lines that were perfect to use as guides when we moved the globe for each frame. When photographing the globe we had to be careful not to skip a section or double up on one.
One person moved the globe and carefully stepped out of the frame so that the photograph could be taken. This process was repeated 72 times until the globe was photographed for one full rotation. When the photographing was complete, the exhibition preparation crew lifted the globe onto a type of dolly and rolled it out of the studio. They then replaced the door.
The next challenge was deciding how to stitch the photographs together and present them online in a usable and accurate way. We settled on using Flash because Flash is a widely adopted tool that most browsers support without the need for add-ons or plug-ins; the necessity of downloading add-ons often prevents people from accessing new multimedia.
We reviewed several online Flash tools and settled on one created by YoFLA because it was easy to use and provided several functions we wanted, including the ability to zoom, a customizable look, and predefined hotspots (or clickable areas.) YoFLA 3D Object Rotate is freely available for those who want to try it.
The first 3D object we created with 72 uncropped images was prohibitively large. To keep download time to a minimum, we created a smaller object with only 36 images that were cropped. Finally, we had a virtual globe that could be put online for easy viewing and close inspection.