QSI 520c Betriebsanweisung PDF herunterladen (Seite 41)

QSI 500 SERIES USER GUIDE

of diminishing returns. Combining 18 frames will not yield a final image twice as good as

combining 9 frames.

Also note that in some cases, doing a “median combine” rather than an “average combine”

may yield better results. A median combine is recommended if several of the individual

frames have unique anomalies such as bright pixels caused by cosmic rays, satellites,

airplanes, etc. With at least 5 images, a median combine completely eliminates extreme

pixel values that occur in individual frames.

Color images

Unless you’re using a single-shot color camera such as the QSI 583c, producing color

images requires taking separate exposures through different colored filters and then

electronically combining the separate color channels. The most common method used by

amateur astronomers for color imaging is called LRGB, where separate color images are

taken through red, green and blue filters and combined with a set of “luminance” images

taken through a luminance filter. The luminance filter is required because CCDs are

generally responsive to frequencies of light that can’t be seen by the human eye. The

luminance filter blocks the infrared (IR) and ultraviolet (UV) frequencies that fall outside the

range of human vision.

The luminance filter transmits most of the visible light coming from the object. Because the

individual frames taken through the red, green and blue filters block roughly ⅔ of the total

visible light, the luminance image will often reveal subtle details not apparent in the

individual color frames. This actually works out quite well since the human eye is much

more sensitive to changes in brightness than it is to changes in color. Combining a color-

balanced RGB image with a luminance image will yield an LRBG image that the human eye

would perceive as being very close to the true colors of the object with more fine detail than

is present in the RGB image on its own.

MaxIm LE can be used with your QSI 500 Series camera to collect and catalog the various

filtered images that you’ll need to create LRGB images. As with any images, you’ll want to

collect multiple frames through each filter and then calibrate and combine them in order to

reduce the major sources of noise. After calibration, you’ll have a master luminance image

plus master red, green and blue images. Those master color frames are combined into

your final image. In addition to the color image tools in MaxIm you can do further

processing of your images in Adobe Photoshop or similar photo manipulation programs to

yield impressive final results.

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QSI 520c Betriebsanweisung Seite 41