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Hello all:

I have encountered some questions that I am not very clear about them. Hope to get your great advice & explanation.
<my ISIS is version 5.1.2>

1). Predefined mode. it has 1200L [6 lines], if this mode can ONLY be used to calibrate Ha zone?

2). For WR134, what should I fill in the "scaling profile spectral region " in the "Settings" Tab? I know that its fuction is to normalize the continuum by selecting a region where there is no spectra, no emission or absorption lines. Could you please explain deeply about it?
In addition, in "Profile" Tab there is a button "Normalize", too. what is the difference between them? How to use them correctly?

3). I know that I must redo new Instrument Response for Lhires3 after I change grating, slit,etc.. mechanical parts of it. I have read through the tutorial, but all exampls and contents are for Ha. And all data in the database and libraries in ISIS seem to be used for Ha. Then when we take spectra from other spectral ranges, i.e. 540nm, how to make the instrument response? What are the correct procedures?

Cheers,
Dong

Hi Dong,

1) The ISIS predefined modes only work in the Ha region.

2) If, with WR134, you are working around Ha then the 6615-6620A normalisation range is ok. If you are working at another wavelength you select a short region with a flat and low noise continuum (no obvious lines). The continuum in this selected zone is used as the 'unity' value for spectrum normalisation (scaling). You can rescale (re-normalise) at any time to a new wavelength reference by changing the "scaling profile spectral region " in the "Settings" tab and then clicking the "Normalize" button in the Profile tab ... or reprocessing the spectra with the new values.

3) If you are working in a different wavelength zone to Ha you will need to take a reference spectra using an argon, xenon or other light source. You then convert this spectra to a .dat format ("Spectra processing2' tab/ 'Extract a raw spectral profile') and then use the Profile/Dispersion tool to compute the polynomial values ... these are then used in the 'Predefined dispersion' or 'File mode' options of 'Spectral calibration' on the 'General' tab. Details of this process are given in the ISIS tutorials, but I accept that you have to search carefully to find them.

Cheers, Bernard

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Quicquid Nitet Notandum

Hi dear Mr. Heathcote,

Thank you very much for your explanation! I will try later...

And if I use other kind of grating, such as 150L; 300L;600L etc.... are the procedures for both normalization and instrument response the same to those used for 1200L?

Dong

Hello Dong,

Bernhard has explained it quite well. If you look for the manual calibration (file mode) you find it at the end of this tutorial:
http://www.astrosurf.com/buil/isis/guid ... to1_en.htm
More on manual calibration outside H-alpha you find here:
http://www.astrosurf.com/buil/isis/tuto ... ion_us.htm
and here:
http://www.astrosurf.com/buil/isis/He_c ... method.htm
This should help you.

The spectral lines that you can use for calibration you find e.g. in VSpec or NIST:
http://physics.nist.gov/PhysRefData/ASD/lines_form.html
For the instrument response in wavelength regions different from H-alpha, you can take reference spectra from the database in ISIS. Select either NOAO or Miles library. These are at somewhat lower resolution, but sufficient for normalization. Proceed the same way as for the H-alpha region. Divide spectrum (preferably of a B or A star) by reference, remove atmosheric bands if necessary and smooth to remove noise, then store as response. Make a separate response for each grating, wavelength setting combination.

Regards,

Martin

Hi Martin,

How are you recently? Thank you very much for all these information. But because my PC is Chinese version WindowsXP, I can not run Vspec, NIST seems so professional to me, a little bit confused, can not understand well about it.

I am going to try both your and Bernhard's advice, the links given by you have been read for a few times before, perhaps they are only theoratical, I think that I will understand well about these through WR campaign. you know, however ths is 1st time for me to make spectrum rather than Ha.

BTW a question: I use Neon for 540nm calibration, is the function of neon-lines equal to those of water lines used for Ha?

cheers, Dong