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Christian - The focus (telescope or camera) was not changed from one image to the next. The location on the slit was different by 35x4.54micron pixels i.e. 0.15mm and both were within about 1 -2mm of the centre of the CCD. The reported R>1100 with the 23micron slit which is being well sampled by the...

I have been taking some LISA spectra to learn the ropes and last night I imaged two A stars one after the other for about 1 hour each. I was practicing with fainter magnitudes. I attach an image which is the sum of the sum of the spectra I got as they look starnge to me. They show absorption lines t...

I have been wondering about the use of flats with the latest ISIS software and LISA reduction process. The software averages the flat by column as the LISA’s built in calibration unit’s flat have a gradient even when adjusted optimally. Given this and the reduction process performed by ISIS which de...

Thanks Christian - That explains it. Once I normalise them at the same point it works fine. Regards Andrew

I have done some more investigation. I am using v5.1.0 and find some differencies with the tutorial. Looking at the screen shot which compares the @@.fit with the responce curve looking at the smoothing factor 20 at wave length 4204 my intensity is 0.9 while the tutorial is 0.5316. Also when I displ...

Hi - I have been following the ISIS tutorial but when I compare my reduced Vega spectra with the reference spectrum they don't line up. The same happens if I use my own data. What am I doing wrong. I have followed the instructions line by line!

Thanks Andrew

Thanks Christian I will give it a go. Also thanks Robin for the advice. I think a better quantification of error (S/N and calibration) is the one missing element in our quest for profesional quality spectra.
Regards Andrew

Christian, I was wondering if ISIS could be upgraded to provide an error estimate for the signal level across a spectrum. I had in mind that when stacking several spectra the variation in the level (spectra to spectra) could be used to estimate the noise (variance, standard deviation or standard err...

Robin - I think this will be quite difficult and test even your skills. It will require you to rotate the SA/CCD between fields and in addition as you point out flat fielding on the edges of the field may prove a challenge. However, I am sure you will be up to it.

Regards Andrew

Hi Robin - I am going to try to do both BVRc Photometry and the Lisa for the spectroscopy at the same time using a 140mm for the photometry and my 300mm for the spectroscopy. I have been interested in trying to do both for a while. Unfortunatly one of my cameras has a fault at the moment so I can't ...