Rspec or Bass or…

Forums Spectroscopy Rspec or Bass or…

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    Lars Lindhard

    Inspired by a recent discussion on the danish astronet I have dragged my old, but unused Star Analyser out of the closet and will try to obtain some spectra just find out how it works. 

    I have to calibrate my spectra with an A-star, say the webpages I have consulted.

    How do I do that?  Is there a reference library, where I can find such a spectrum, or must I make a second picture of a known star for the purpose?  If so, can I take a spectrum of Vega once and that’s it?

    It seems that Rspec is a fine and easy-to-use (but rather expensive) program, but people in this forum use the free program BASS?

    Is BASS as easy to use and have the same features as Rspec?  I know, since you use BASS I can guess the answer, but is BASS better than Rspec for a complete novice?


    Andy Wilson

    Hi Lars,

    Rspec is designed to be easy to use but has limited functionality.

    BASS is the next level up. It has a lot more functionality and is a lot easier to use than say ISIS. ISIS is pretty much the gold standard in spectral processing, but is the hardest to use.

    I suggest starting out with BASS as it is free, and see how you get on.

    I also suggest starting simple. The A-type star is used to response correct the spectrum. This is to remove the bulk effect of the Earth’s atmosphere, and to adjust the bulk profile of the spectrum for the telescope and camera sensitivity. Note this doesn’t remove any spectral lines, just large scale features that affect the shape of the continuum. While this is important for getting a correct continuum, I wouldn’t bother with your first few spectra unless you really want to. I took spectra for 3 to 6 months before attempting a response correction.

    When you are ready to do a response correction, then you will need to choose an A-type star at about the same altitude and on the night of your observation. The altitude of the star will affect the response correction as when you look lower down you are looking through more atmosphere. Also, atmospheric conditions can affect the response, so a response taken on one night may not work on another night.

    Most important of all is to keep it fun! Don’t worry about getting things exactly right at the start.

    Best wishes,


    Lars Lindhard

    Hi Andy

    Thank you.  I will start out with BASS and read the BAA-Guide to the program.

    Then when the clouds eventually disappear I might take at photo to work with  🙂

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