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Astroart and FFT

Posted: 14 Aug 2023, 18:57
by Mauro F1
Sometimes images can be affected by electrical noise, visible as regular slanted bands as in this shot of the Sun.
Using the FFT functions they have been eliminated.
Image taken on 15 July 2023 at the oss. Geminiano Montanari in Cavezzo (MPC107). Lunt 102 telescope (H-alpha 0.7nm) and ASI120.

Original image with bands: With [Arithmetic] - [Image -> FFT] we convert the image from the space domain into the frequency domain.
The frequency of the noise is highlighted as a clump of pixels in the FFT image:
We remove the noise either selecting a rectangle and filling it with a value equal to 0 [Image] - [Fill], or with the [Edit pixel] functions, right-clicking with the mouse button on the image, then using the Paint functions.
The result will be as the image below: Now we will reconvert the image from the frequency domain to the space domain with [Arithmetic] - [FFT -> Image]. The periodic noise has been eliminated: Image processed with [Filters] - [Multiscale High pass]: Mauro F1

Re: Astroart and FFT

Posted: 15 Aug 2023, 04:24
by Dunmunro