many thanks Gary for your prompt reply!
Well, since you have the spectral data for this filter, i don't really care about the "KG3" thing anymore
Based on the transmittance spectrum, I have the feeling that this filter is really oriented toward sun work as the transmittance, even in the "open" bandwidth between 400 and 700nm, is relatively low (60 to 90%) as compared to "classical" webcam IR/UV filters (close to 100% between 400 and 700nm).
Unfortunately, transmittance is critical for me as I have only a small aperture, "long" focal, refractor (80mm-900mm) and I want to do planetary imaging with a webcam

.
Please correct me if I am wrong, I am really a beginner.
Thanks anyway for providing the relevant information, much appreciated.
Cheers,
Joel.