Specifications

Open the “Histogram and Stretch” tool .
Illustration 15: Histogram and Stretch tool
The exact meaning of the histogram chart is explained in the SIPS software
documentation. Now only try to play with “Low” and “High” count-boxes
or better with the related horizontal sliders. Observe how the image view is
changed when you alter these values.
The best positions of Low and High control are as follows: the Low count
should be on the count value representing black on the image. Any pixel
with value lower than this count will be displayed black. The High count
should be on the count value representing white on the image. Any pixel
with value higher than this count will be displayed white.
Similar adjustments are usually called brightness and contrast adjustments.
● Brightness is changed by moving both Low and High values
together up and down. Try to move both values using the second
slider below the histogram chart.
● Contrast is changed if the relative distance between Low and High
values changes. Try to narrow or widen the distance between Low
and High values.
But astronomers often need precise control of Low and High values so the
terms brightness and contract are not used within SIPS.
Calibration
If you preform short exposure of bright object, the signal to noise ratio of
the image is very high. Image artifacts related to CCD chip (like hot/cold
pixels or thermal noise) almost do not affect the image. But all unwanted
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