Unsharp masking can be used to significantly enhance the detail visible in certain objects. It can also easily make an image hideous. The process is often overdone for no apparent gain. However, on some objects, the technique of super-unsharp masking...
Harold Nyquist is at the center of a raging CCD debate. Nyquist died, by the way, about the time CCD cameras were first being used by professional astronomers, and nearly two decades before they became popular with amateur astronomers. So...
Color in astronomical images has long been the subject of much debate. The basic ideas behind "true color" imaging are outlined below, and tips are presented for capturing better color CCD images. Color in Astroimaging The real problem with color...
Capturing faint detail in deep-sky astronomical images is all about overcoming noise. Noise comes from a variety of sources: Heat (dark current) CCD readout Light pollution/sky background Cosmic rays Pixel defects Optimal images will reduce these noise sources as much...
Flat field images are used to remove uneven illumination from images. Primarily this means removing vignetting, which darkens the corners of an image. With larger-format cameras, including digital SLRs, the fast focal ratio of the HyperStar lens can cause some...
Zoom eyepieces offer a convenient method of changing magnification without having to use multiple eyepieces. Unfortunately--there being no free lunch and all--there is a trade-off in optical quality when using a zoom eyepiece. Above: A typical zoom eyepiece, TeleVue's 8-24mm...
Taking the Image A CCD (charge-coupled device) is an electronic instrument for detecting light. In the case of an astronomical CCD camera, this light is very dim. We will see that this has certain implications for how the CCD operates....
The advent of amateur CCD imaging has opened up a whole new world for astronomy enthusiasts. Astronomy is the one science left where amateurs still make an important contribution. The reason is simple: there is too much universe for just...
Film astrophotography began in the late 19th century with photographs of the moon, sun, and bright stars. Film then was thousands of times slower than it is today. While film became faster and faster, the technology itself changed very little....
Digital cameras, digital video cameras, and webcams all use CCD chips (or similar CMOS chips), just like an astronomical CCD camera. They are also incredibly popular, with millions being sold every year. So the obvious question is whether these types...
The refractor is the oldest telescope design. It is by far the most familiar design (it's what Galileo used in the 17th Century, and it's what Marvin the Martian used in the cartoons). Refractors have been used to produce some...
