Flux calibration and Spectrophotometry

[Tony Rodda]

I’ve been working through Christian Buil’s more complex ‘four spectra’ process for flux calibrating spectra.

Attached is a workflow I’ve compiled from Christian’s notes – as an aid to my learning process.  If anyone has already done this I’d appreciate comments/amendments/corrections.

It’s ‘work in progress’ as they say.  I’ve had mixed results but just in terms of the odd attempt going astray.  Its getting to the point where I can replicate results.

The aim is to produce reliable BVR magnitude measurements from regular observations by adding a few minutes of ‘Alpy photo slit’ exposures to the process.  The Alpy lends itself to that application.

Regards

T

Attachments:

1. 

   Spectrophotometry-In-ISIS.jpg
   

[Paul Luckas]

Hi Tony,

I’ve only had a cursory look at your workflow, but it looks pretty thorough to me.

The ultimate test of flux calibration accuracy is to compare your result with a standard. The CalSpec standards (some available in the ISIS database) can be use for such comparisons. 

Paul

[Robin Leadbeater]

Hi Tony,

It will be interesting to see how your results compare with conventional differential photometry.  It will give us an idea how accurate absolute flux calibration from a typical amateur observatory actually is.  The difficulties compared with conventional differential photometry  are you are dependent on stable atmospheric conditions and  because suitable reference spectra calibrated in absolute flux are rather widely spaced, differential extinction has to be taken into account – the spectroscopic equivalent of all sky photometry.

Cheers

Robin

[Tony Rodda]

I’m experiencing a few gremlins with calibrating the 230 um spectra but generally results are looking repeatable.

I just need three times as many clear nights as I’m getting!

Regards

Tony

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