Capture the Moon in high resolution
Few technological advances have impacted astronomy as much as the digital revolution. It’s been true in the professional field since the 1980s, and it’s been true for amateur astrophotographers like us since the turn of the millennium. Perhaps nothing illustrates this seismic shift more clearly than comparing historic photographs of the Moon with their more modern counterparts.
For example, take the large lunar crater Clavius, photographed in the 1950s with what was then the world’s largest telescope, the 200-inch Hale Telescope at Palomar Observatory. If you compare this photo with a corresponding image taken in 2005 using a standard consumer 14-inch oscilloscope and one of the first commercially available CCD cameras, the differences in resolution, sharpness, and range dynamics between the two are striking.
So what are some of the cutting-edge lunar imaging tools and methods now available to those with amateur-sized telescopes (6-14 inches)? Besides good optics and a solid mount, most practitioners can use a number of excellent webcam or laptop models (with appropriate image capture software), as well as sophisticated stacking and image processing. Additionally, for close-up, high-resolution imaging of certain lunar features, quality Barlow or Powermates lenses—both of which extend focal lengths—are essential, as are atmospheric dispersion correctors and, usually, near-infrared filters. to minimize the effects of less than perfect viewing conditions.
Shooting from his home near Brussels, Belgium, one of the authors of this article, Leo Aerts, regularly uses a 10-inch f/15 “planetary” Schmidt-Cassegrain Opticon (with only 25% central obstruction) and a Celestron 14 -inch f/11, both on Losmandy G-11 mobile equatorial mounts. The telescopes are stored in the garage of his house and wrapped in heat-insulating material to prevent overheating during the day.
Although Aerts used many older webcam models, including several DMK CCD models, they operated at relatively low capture rates of 30–60 frames per second (fps). His current favorite cameras are the ZWO CMOS models, a 178MM ASI with a 2.4 micrometer (µm) pixel size and a 290MM ASI with 2.9 µm pixels. These models perform very well up to 150-250 fps, with low noise levels and high IR sensitivity. Aerts also regularly uses an AstroTechniek atmospheric dispersion corrector, especially when his target is below 40° in the humid Belgian sky. These handy optical devices have two rotating silicate glass prisms, which can be adjusted to introduce a degree of native chromatic aberration that counteracts that of our atmosphere.
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