Contrast enhanced crescent observation

11.06.2010, Martin Elsässer

The special version of the Lucam Recorder software for Contrast enhanced crescent observation could be tested on a difficult lunar observation.

Situation and visual observation

On the morning of 14.04.2009 the moon was only about 4° above the horizon and the sky was quite milky.
The moon could not even be seen visually, with naked eye or 8x56 binoculars, despite being almost full.
This resembles a situation with a VERY low contrast crescent.
moon with common DSLR
The position of the moon, captured with a common DSLR at the same time as the series of demonstration images was taken. This resembles naked eye observation, where the moon was NOT visible.

contrast enhanced red-channel of the DSLR image
After strong contrast-stretching in the red-channel of the DSLR image, the moon can be made visible in the image.
Not really obvious though, so no surprise it could not be seen visually.

Demonstration of the Lucam Recorder software

A small and inexpensive telescope (70mm diameter, 400mm focal length) was equipped with a simple red filter and pointed at the position of the moon.
A monochrome camera was attached to the telescope and operated through the special software.

raw image of the moon
The moon was barely visible on the screen, due to the very low contrast in the milky skies, despite the red filter.

contrast enhanced image of the moon
The software was configured to increase the contrast of the captured images, making the moon very well visible.
This contrast enhanced view is visible in real time, as live image!
The shadows of dust particles on the optics and variations in sensor response also became quite visible.

flat field
A previously captured flat-field image was applied in real time, removing the dust-shadows and inhomogenities.
The flat-field can easily be taken in the field in just a few seconds, by moving the telescope slightly off target.

To reduce the visible noise and inrease visibility of faint detail, the software was additionally configured to automatically stack individual images, displaying the average as live-image.
Despite only stacking 4 images, the noise is visibly reduced.

contrast enhanced
The contrast was increased further, to take advantage of the noise-reduction acchieved through stacking.
Compare this LIVE-image to the raw image at the top, to see the dramatic improvement.

A step by step example of how to use the Lucam Recorder software.

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