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Hi Christian Thanks for your reply and explanations. If I understand well, you prefer to measure atmospheric absorption at the zenith and to make use of a mathematical model to extrapolate this measurement to other zenithal heights rather than relying fully on a mathematical model of this absorption...

Yes Andrew, I do agree. The fact that the spectral response of the flat shows up at the denominator led me to replace convolution by deconvolution, having in mind that multiplication and convolution are associated notions (through a Fourier transform).
Patrick

Yes Andrew, I think you are right, if your flats are raw flats and if convolution stands for deconvolution.
Regards.
Patrick

Thanks Christian for your interesting study. However, I do not understand how this new study is related to the previous one : http://www.astrosurf.com/buil/extinction/calcul.htm in which you proposed a procedure to account for the absorbing effects of the atmosphere. What makes the recent procedure ...

After carrying out a detailed analysis of the lines shown by the neon calibration lamp between 3900 and 4300 A, I made extensive experiments to reduce the inaccuracy mentioned above and I conclude that the attractive approach suggested by Benji seems hopeless. We cannot avoid using the Balmer lines ...

Hello, - With a deg 4 polynome and the following lines: 4065.65, 4348.06, 4710.06, 5400.56, 5852.49, 6402.25, 7032.41, 7245.17, 6143.06, 6678.28 and 6929.47, Benji I tried to calibrate my low resolution spectra using these lines but the result shows an inaccuracy of about 5 Angstroems in the blue. ...

Nice work Benjamin. I hope repeated long neon exposures are not harmful for the acquisition camera... Also I am afraid we still lack calibration wavelengths between 4348 and 5341Angstroems. This may hamper the accuracy of a high degree (>3) calibration polynomial.
Patrick Lailly

A couple of weeks ago, my Lisa caught its first light behind a C8 and in front of an Atik 314L+ camera. At first glance, tuning such an acquisition chain looked straightforward. According to a recent post by Emmanuel Thienpont on Spectro-L, along with the reply by Francois Teyssier, it is not that s...

I roughly agree. Thanks Christian.
I will not miss submitting reasonably oversampled spectra to Bess.
Patrick

Merci Christian pour ta réponse très complète. Petite précision préalable : j'avais mis du scotch alu sur certaines fentes de mon Lhires et, confiant, je prenais mes flats sans enrober mon spectro d'un drap de photographe. Mais, comme le montre l'image ci-dessous, mes protections au scotch sont insu...