14. Noise reduction (options panel)
–
Noise reduction is an advanced feature
of Registax. At the wavelet-page under
options you can set the checkbox "Noise
reduction". The noise reduction window
will appear. This has a set of sliders and
checkboxes for every corresponding
wavelet layer. The sliders control the
"cutoff"- pixel values in a layer, values
below this cutoff are not used in the
images (the preview buttons do show this
too). The checkbox allows you to decide
which layer(s) you want to de-noise. First enhance a single wavelet layer with its
default slider (right-side of the screen). Choose a noisy layer (the 1st) to test
things. Then set the checkbox in the noise reduction window for this layer on.
Now you can select several methods to reduce noise just choose them and see
what they do with your image. When you have found one you like then turn over
to manual. Now play with the slider belonging to the layer to refine the settings.
Anti-ringing (Noise reduction window)
– when you set the checkmark it
will already filter all values below zero out of the image. Often that is unwanted
since we want only the "ringing" around stars removed. Point your cursor at
a "normal-dark" background area, than press the RIGHT-mouse button. This
makes the program estimate the background level, every value of the image
below that level is considered to be "ringing" and will be replaced with data
from the stack directly. The slider allows you to alter this estimated level manually.
15. Histogram Stretch & RGB
(checkbox)
– This feature allows you
to use a Histrogram stretch technique to
enhance the images. When checked, the
Histrogram-window appears. The two
checkboxes control the graph of the
histogram. Smooth takes the spikes out of
the graph and show peak ensures that the
highest value is still visible. The red and
green triangles control the histogram-stretch
operation. When you slide them and press
"stretch", the image will change its
appearance. Reset brings everything back to
the original positions. Now the window also has weights for the R,G,B channels, these
weights together with the RGB sliders allow you to tune the colours of the image (to let
peaks in the RGB channels for instance coincide). The sliders and the weights together
form the contrast/brightness settings per color-channel.
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