I have had a very rough 2 months unfortunately health wise. I was struck 3x in a row with bacterial infections. The second infection occurred  after a routine hospital checkup and I became very sick. I had to rest and take a lot of antibiotics. Once I was recovering and restarting work 1 month ago, I again became sick. The infection was not yet gone, so even more antibiotics and rest was needed. Needless to say, it took a lot of my energy and I needed a lot of rest.
Finally, the infection is really gone and my energy is coming back step-by-step now and I have started work again. I am terribly sorry to have kept you waiting for support. I will address all outstanding questions and e-mails step-by step and will be on the forum daily from today.
APP 2.0.0-beta47 will come soon as well, a lot of work was already completed before I became very ill, so the release is also nearly ready for you. Beta47 will be much faster actually. Many workflows will be more than 2x faster, mosaics can even be 10x faster than before because registration really received a major boost... all compared to beta46. Â Before I release it, I will make sure that everything is working properly and then I will release it.
[Solved] Interpolation artifacts with Lanczos, Catmull-Rom Spline, Mitchell-Netravali, Cubic B-Spline
I'm getting little bit of interpolation artifacts for the data set that I'm working with.
There are dark pixels at the edge of some stars when I use Lanczos-3 as the interpolation algorithm.
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In fact the artifacts are a lot worse in Pixinsight.
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They are much less noticeable with APP.
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If I use bilinear algorithm, the artifacts go away but the image is not as sharp as one from Lanczos-3(bigger FWHM value).
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I'm wondering if there is a way to preserve FWHM but remove the artifacts.
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Thank you very much.
Donghun
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Hi Donghun,
Yes, I clearly see the artefact. This artefact is known as undershoot. This will always happen with a data interpolation algorithm like Lanczos.
But there is a solution to prevent this in APP. You will need to enable the "no under/overshoot" selectbox below the pixel interpolation filter in 6) INTEGRATE. This should prevent these dark pixels at the star borders due to undershoot.
Let me know if this solves the artefacts with your data.
Mabula
Under and Overshoot happens because a filter like Lanczos has positive and negative lobes see:
