BETHLEHEM, Pa. — Brad Klein reviews upcoming astronomical highlights with Bethlehem’s "Backyard Astronomy Guy," Marty McGuire.
For November, we’re taking a look at comets, with three getting a lot of attention as they pass through our inner solar system. This week, the subject is astrophotography.
If you spend any time on online astronomy sites, you will see some spectacular photos of Comets 3I/ATLAS, C/2025 A6 (Lemmon), and C/2025 R2 (SWAN).
Comets are difficult to photograph even by the high standards of astrophotography.
They are small, far away, and don’t give off any light of their own. But as they near the inner solar system, the warmth of the sun can sometimes create a highly reflective "tail" that is propelled away from the comet by the solar wind.
Since every comet is different in size and composition, it is hard to predict in advance whether a comet will be bright enough to see with the naked eye, or remain so dark that only the best telescopes can make it out.
McGuire was able to create a modest image of comet "Lemmon" recently from his home in Bethlehem. He used a technique called "stacking" along with a good backyard telescope and a tripod.
After taking some 75 individual photos of the comet, he manually aligned them using Photoshop. That created the equivalent of a much longer exposure, without having the movement of the Earth’s rotation interfere with a sharp picture. The result shows hints of the comet’s tail, along with background stars, and even a plane or satellite passing through the image.
For even more detailed photographs, it is possible to combine stacking with motorized tracking of an extraterrestrial object, so that the camera and telescope combination can make much longer exposures.
“Those are the major techniques in astrophotography, and it takes a while to master some of those skills,” McGuire said.
The government shutdown has prevented NASA from operating all its social media sites, but we can hope for some stunning comet photos to appear from the space agency on its social media accounts, once the deadlock in Washington has passed.
