Add Noise; Stretch Image - Meade Autostar Software Manual

remove them. When you select this command, a dialog box will appear. This dialog allows you to set how
aggressively the program hunts for bad pixels. The smaller the threshold number you supply, the more
aggressively, the filter will act.

Add Noise

This command can be used to make cosmetic improvement to an image's appearance. Adding a small
amount of noise can cover up minor defects. It can also disguse the problem of areas with gradual
changes in brightness; the human eye is very effective at detecting the shift from one color level to the
next, resulting in a banded or contoured appearance (Mach bands). This problem can sometimes be seen
on planetary limbs, or in solar limb darkening. This visual effect can be eliminated by adding a small
amount of random noise.
When you select this command the following dialog appears:
Use this dialog to select the mean amplitude of the noise you wish to add to the image. Additionally, you
can select the distribution of the noise added. The noise can be wither uniformly distribute (white) noise, or
gausian noise. When you click on OK, these random values will be added to each pixel in your image.

Stretch Image

Stretching a image is the process of applying an algebraic function to each pixel in an image. This
process can be used to emphasis or de-emphasize highlights, or simply clip and scale image values.
Autostar IP offers several different scalings:
Log Scaling replaces each pixel with the log of its value. This has the effect of stretching the contrast to
favor details in the image highlights and increases the dynamic range of the image that can be displayed.
Exponential Scaling replace each pixel with the e (the base of the natural logs) raised to the power of the
pixel value. This stretch flattens detail in highlights. It is also helpful in reducing limb darkening effects.
Gamma Scaling replaces each pixel with its square root. This stretch is similar in its effect to log scaling,
but is not as aggressive. It helps increase the dynamic range of an image.
Linear Scaling, when selected brings up the following dialog box:
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Autostar IP