With the default settings, this noise filter is efficient for visualization and publication in Internet. But once print with a sheet of paper or in photo paper, it proves too strong and some artificial textures appear in the sky background. It must be softened by a manual setting for astrophotography. Luminance at 50 and Chrominance at 70 seem to be good adjustments.
Par contre, il fonctionne très bien en photo classique.

Let's test its efficiency.

The noise is very soften. At the naked eye, the result is good, but some wooly areas appear in photo prints or with a printer. It is needed to use the manual mode and find the good settings for all kind of media.

On the right: RAW file (crop at 100 %) before and after noise reduction.
Canon 350D + Sigma 18-50 at 18 mm open at 2.8 on a tripod. 30 s at 800 ASA.

The right picture show this wooly texture appearing when the anti-noise filter is too strong. The luminosity and the contrast of the picture have been strongly increased to show at best this defect. I must tell you that this picture zoning was ever visible in the RAW file. But, mixed with the noise, it was less visible.

Canon 350D + Sigma 18-50 at 18 mm open at 2.8 on a tripod. 30 s at 800 ASA.