Meade Autostar Software Manual page 16

Image processing
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Setting the Brightness control to values greater than zero brightens the image, while values less than
zero will darken it. Generally, you must use both the contrast and brightness controls together to achieve
the desired results.
The Linear function sets a straight line transformation that resets the contrast and brightness values to
1.0 and 0.0 respectively.
The Dynamic function analyzes the image for its lightest and darkest values (excluding pure black and
white) then sets up a linear transformation with the contrast and brightness adjusted to provide a full range
image. This is useful on images that are over or underexposed, or those that have poor contrast.
The Exponential function sets a non-linear transformation and resets both contrast and brightness. The
resulting exponential curve produces images that have lower contrast in the dark areas and higher
contrast in the light areas. This is useful for bringing out detail in the central regions of galaxies or
nebulae.
The Logarithmic function produces a curve that is the inverse of the Exponential. It increases the
contrast in the dark areas while lowering it in the bright areas. This helps to enhance the detail in the faint
arms of a galaxy.
The most complex transformation is Histogram Equalization.
Its purpose is to construct a
transformation curve that shows the maximum amount of detail in the image in all areas.
This is
accomplished by building a Histogram of the image (counting the number of pixels at each brightness
level), then constructing a curve that tries to equalize the number of pixels in each of the resulting
brightness levels.
The maximum number of resulting levels can be set using the scroll bar, a greater number of steps
generally produces a smoother image. This value must be set before the Histogram Equalization button
is pressed. The maximum value is seldom reached since the equalization process greatly reduces the
number of initial gray levels. The default value of 128 is useful in the majority of cases since most images
tend to equalize to fewer than 64 steps.
Histogram Equalization is useful in almost all images, but remember that the resulting curve is far from
linear, so that further quantitative analysis (e.g., Magnitude determination) is impossible.
The Posterize function produces a stair stepped curve that can reduce the number of displayed values to
the predefined settings. By setting the number of steps with the scroll bar, depressing the Posterize
button displays the resulting curve and resets the contrast and brightness values. This feature is most
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