Handbook for the TRIUS PRO-825C Issue 1 September 2020
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Image enhancements:
Your first image may be satisfactory, but it is unlikely to be as clear and sharp as it
could be. Improved focusing and exposure selection may correct these
shortcomings, and you may like to try them before applying any image enhancement
with the software. However, there will come a point when you say, “That’s the best
that I can get” and you will want to experiment with the effects of image processing.
In the case of daylight images, the processing options are many, but there are few
that will improve the picture in a useful way. The most useful of these are the
‘Normal Contrast Stretch’ and the ‘High Pass Low Power’ filter. The high pass filter
gives a moderate improvement in the image sharpness, and this can be very
effective on daylight images.
Too much high pass filtering results in dark borders around well-defined features and
will increase the noise in an image to unacceptable levels, but the Low Power filter is
close to optimum and gives a nicely sharpened picture.
The ‘Contrast’ routines are used to brighten (or dull) the image highlights and
shadows. A ‘Normal’ stretch is a simple linear operation, where two pointers (the
‘black’ and ‘white’ limits) can be set at either side of the image histogram and used
to define new start and end points. The image data is then mathematically modified
so that any pixels that are to the left of the ‘black’ pointer are set to black and any
pixels to the right of the ‘white’ pointer are set to white. The pixels with values
between the pointers are modified to fit the new brightness distribution. Try
experimenting with the pointer positions until the image has a pleasing brightness
and ‘crispness’.
At this point, you will have a working knowledge of how to take and process an
TRIUS PRO-825C image. It is time to move on to astronomical imaging, which has its
own, unique, set of problems!
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