What is the fine-grained topic of the following text: In the months since the eclipse, we have used computers to pick out the best part of dozens of the images to make extremely high-contrast images that allow us to measure motions at extremely high speeds in the corona, as we compare our composite images with some made by co-ordinated colleagues 65 minutes farther east along the path of totality,” Pasachoff said. Only return the topic.
Analyzing high-speed motions in the corona post-eclipse using high-contrast images