In the Image Processing Basics section on Calibrating Images we discussed only one type of image calibration -- dark subtraction. This is the most important calibration step, but not the only one that can be performed. Other techniques include using...
Combining images was covered briefly in the Image Processing Basics section. Here, more detail is given on methods for combining multiple images to increase detail and to reduce noise. Methods for Combining Images The simplest way to combine images is...
We touched on high-pass and low-pass filters in the Image Processing Basics section. Here we go into more detail on more advanced filters such as unsharp masking, low-pass filtering for noise removal, and filters for reducing image artifacts. Unsharp Mask...
well as other color image techniques such as LRGB and CMYK imaging. Advanced RGB Techniques The basic idea behind RGB imaging is to combine three images taken through red, green, and blue filters. This creates a full-color image. Since color...
The following is a simple procedure which can be used to enhance faint detail in an image while preserving detail within bright regions of an image. This is particularly useful for bright nebulae (such as Orion or the Swan) or...
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...
