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ALPY ArNe 14.lst

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Nick Atkinson's picture
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Joined: 11/03/2014 - 23:17
ALPY ArNe 14.lst

Andy David & John,

Thank you very much for organising the spectroscopy workshop in Birmingham and posting the talks on the videos of meetings sections by David and John.

In the General Tab option 1 is the predefined mode and I have had no issues.

However, in the file mode using  ALPY ArNe 14.lst 1k file I have encounted errors. Please enlighten me on how this file was generated and should it be used in spectra that I obtain

Clear Skies

Nick

David Boyd's picture
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Joined: 05/03/2014 - 09:02
ALPY wavelength calibration

Hi Nick,

This is based on a .lst file I was originally given, I think by Olivier Thizy when he was at Shelyak, containing emission lines which are present in the Ar/Ne calibration lamp which they supply.

To use it with ISIS you select file mode in the General tab, type the .lst file name in the box, and then on the Calibration tab you specify the wavelength of one of the lines in the calibration lamp spectrum in the "X coordinate of line at wavelength" box. I use the line at 5852.488 A which in my calibration lamp spectrum is the brightest line close to the middle of the spectrum. Then place the cursor over the centre of that line in the display of the lamp spectrum below and double click. ISIS then fills in the X coordinate of that line in the adjacent orange coloured box. When you then hit "Go" it should correctly identify the location of all the other lines in the .lst file and wavelength calibrate your spectrum.

If you still have problems email me off list and I will try to help further.

David

Robin Leadbeater's picture
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ISIS file mode

I use the predefined mode with my ALPY but I use the file mode quite  a bit with my LHIRES for cases where there is not a preconfigured setup. As well as the list of lines, the file contains the order of the fit you want and the approximate linear dispersion needed to approximately locate the lines so it is specific to a particular spectrograph and camera combination.  You can generate your own file by doing a manual linear calibration first using the set (or subset) of the lines and noting the linear coefficient. (or you could try the linear coefficent from the fit generated using the predefined mode)This is then added to the list of line wavelengths along with the order of fit you want. (Note that it can fail if the dispersion is sufficiently non linear and the lines so closely spaced that the wrong line is picked.  To avoid this, I suspect the predefined mode for the ALPY may allow for the non linearity of the instrument which the file mode does not allowing some more close spaced lines at the blue end to be used.) A typical file for the LHIRES looks like this for example 

2

0.2461

6532.882

6598.953

6717.043

6752.834

where 2 is the order of the fit and 0.2461 is the linear dispersion (A/pixel)

(Ignore the doublespacing generated by the forum software)

Cheers

Robin

Robin Leadbeater's picture
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instructions for file mode

Here are the instructions given by Christian Buil for generating a file for use in file mode (method 3)

http://www.astrosurf.com/buil/isis/tutorial/calibration_us.htm

Robin