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Bernard, Robin, I suspect these are interference fringes which are formed via multiple reflections within the spectrograph and or CCD camera. Robin’s example of variation with binning height tends to confirm this as this will change the optical path length. It may be that deliberately de-collimating...

Christian - It might be worth repeating the experiment using the Atik capture software "Artemis Capture" to avoid the complexities of your current set up. It just might be an issue with the camera firmware. I also just remembered that on my Starlight Xpress MX7 it changes it's mode of taki...

Christian - I am puzzled by your first graph i.e. linear fit to the data. All but one or possibly two of the points are above the line so I doubt it is a best fit. Did you do a linear regression or some other method of fitting the data? While this may not invalidate your findings the errors may be s...

I have built a slitless spectrometer with dispersion similar to the star analyser but it does not show the zero order image for a centrally placed star. Is it still possible to process the spectra in ISIS and if so which option is best? The field can be quite crowded and there is significant vignett...

Thanks - Francois - Andrew

I would like to know if bad pixel removal (say via using the bad pixel mapping in MaxIm DL) is acceptable in processing spectra. Also, if it is acceptable when in the reduction process should it be done?

Thanks Andrew

Hi – I am Andrew Smith and fast approaching 60. Having retired I now have time to implement all those astronomy projects I bought bits for but never had the time to do. I have recently built an Imaging Low Resolution (R~200) Spectrograph which allow imaging, photometry and long slit & slitless s...