Crescents in April 2025

Young crescent on 28. April

The crescent was quite easy at 9° elongation, so i played with some features of the Crescent Viewer software to create a kind of demo. I used a simple 80/600 ED refractor telescope with a simple affle system and deep-red filter.

Standard features

Raw view of a stack of 180 images, from one of the automatically saved FITS files. Contrast is very low, of course, as we are close to the sun.

Adding some more contrast stretching in the FITS viewer. There is a crescent there, but we also see various dust shadows and a horizontal pattern and of course the structures of some high-altitude clouds so close to the sun.

This is the live-view the software shows for the situation above. Most technical issues are gone, the contrast is dramatically improved and the crescent is easy to see. The user does NOT need to adjust many settings to get this, just capture some proper calibration data (which can be reused) and choose a Processing Mode.

Experimental improvements

Some more improvements are in the works and are being tested...

The software can automatically search for and mark the crescent in the image. This was a very easy case, of course.

This search-and-mark often still works if some disturbances such as contrails move through...

This was the raw stack of the image above with the contrails and some simple contrast stretching. NOT so easy to see without the special methods...

The crescent search also allows align on the moving crescent and thus stack far more images. This might make very faint crescents visible, but this is not a good example of that.