stacking with the Star Analyser

Forums Spectroscopy STACKING stacking with the Star Analyser

Robin Leadbeater

Hi Peter,

I agree with Andy.  The multiple images of the zero order means there is movement between the individual images. This is normal in unguided images. When stacking unguided images you need to align them to remove blurring due to drift.  ISIS has a tool for doing the alignment (“Tools”, “Image Processing 3”, “Register”)   But with the Star Analyser, the various programs that are typically used by the  planetary imagers are more commonly used to produce  an aligned and stacked image before extracting the spectrum. (You can use  the zero order for the program to lock onto)

These programs also allow you to select the sharpest images and just align stack these which is  another trick we can borrow from the planetary imagers  to get a sharp noise free image when using the Star Analyser.

How much improvement stacking gives depends on the noise in a single exposure. In this case the features are already clear in a single exposure so stacking may not make that much difference.



EDIT:- just seen John’s post which came in while I was typing.  Two techniques to try in ISIS 🙂