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I have pondered long on the use of flats with slitless spectroscopy. I know they are used but can’t see how they work correctly. In conventional imaging or in slit spectroscopy (with a perfectly flat field illumination source matching the focal ratio of the telescope) the light falling on a particul...

Hi Robin - I don't know the answer to your question. However, is the effect you discribe not part of the instrument response? Given in reality the IR will never be uniform so won't you always need to correct for it anyway to get an estimate of the continum?

Regards Andrew

As I mention on another site, well done Robin. I was interested in your setup. I looked at the link on your site but coud not see what spacing you were using to get the 17A/pix also if you used a correcting prism or just the SA100 and or any IR/UV cut filters?

Thanks Andrew

Well I got this close to taking a spectra of RY Tau when the fog rolled in and terminated the observations! Andrew

To anyone following this the problem seems to have been that I did not have the CCD close enough to the position specified in the LISA manual. Having set it as close as I can to that value the spectra are now as I would have expected. Thanks Andrew

Hi Andrew (and Robin !) About reference star, it's clear that we nead a brighter star than those proposed by Darryl Sergisson. Darryl agree. We have to take more spectra from several observers in order to build a common protocol, noticely reference(s) star(s) For my last acquisition, I used HR1490,...

Nice start Robin. Have you given up on using the requested comparison star or have the researchers accepted the use of other reference stars? It was not clear to me if they want raw or corrected spectra of the target and reference stars or just target stars corrected by an acceptable reference. What...

Rainer - I see you are refering to the LISA camera lens - yes I have already focused it onto my CCD. Regards Andrew

Hi Andrew, That is exactly what I get when the star is not focused correctly on the Slit. Did you focus the main lens first and then the slit image in your guider cam ? You can easily focus with daylight your main lens of the LISA. From my experience it has nothing to do where the H-alpha line is p...

Thanks, Robin and Christian. Robin you may well be right and the column correction is probably a normalisation rather than an average which would not invalidate it's use as I thought.
Regards Andrew