Sheratan (beta ARI)

[James Foster]

In pursuit of getting another bright A-type star (now that Vega is gone)
for image response (IR) of my Spectroscope with the 1800 l/mm grating, here
are some spectra (all Normalized except the CaK spectra) of Sheratan:

CaK region:


H-gamma region:


H-beta region:


H-alpha region:


Any feedback appreciated.

James Foster
Los Angeles, CA

[Robin Leadbeater]

Hi James,

Do you have a reliable reference spectrum for bet Ari? It looks like all those metal lines (presumably from the companion K star) will be tough to cancel accurately. From here (Northern England) for bright stars for high resolution work I generally use Castor and then Regulus when Vega and Altair are not around, which have good quality UVES reference spectra.
http://www.eso.org/sci/observing/tools/ ... tonow.html

Cheers
Robin

[James Foster]

To: Robin,

Thanks for the reply. I'll try Castor and/or Regulus for IR.
In reply to your question, I used the A5V miles spectrum to divide by my Sheratan spectrum
to get my IR. I avoid tracing the "obvious" absorption/emission spikes as seen in my example here:
Vega centered near CaK line......(images 01, 02, 03, 04; only 04 labeled):
01: Ne-Ar, 02: Line calibrated Vega spectrum, 03: Miles A0V spectrum, 04: image 02 divided by image 03:



I did see some change when I applied my older (Vega, 19Sep16) IR than the Sheratan derived IR.
Not sure if its because of the different A-stars used or my optics getting "dirtier" from the
nearby freeway and/or humidity sticking dust to my exposed optical surfaces!

James

[Robin Leadbeater]

Hi James,

beta Ari is not a MILES star. Do you mean the Pickles generic A5v spectrum ? beta Ari is a binary has a mixed spectral type so will probably not match a generic A5v spectrum very well. In any case Pickles and MILES spectra are not ideal when working at high resolution because the resolution is too low to follow the line profile well. See Paolo's comparison here for example
http://www.spectro-aras.com/forum/viewt ... 582&p=7278

Good sources of high resolution reference spectra are UVES POP
https://www.eso.org/sci/observing/tools ... rface.html
and ELODIE 3.1
http://www.spectro-aras.com/forum/viewt ... f=8&t=1369

Robin

[James Foster]

To: Robin,

I did use the generic A5V that was in the Miles/Pickles catalog under Bass1.94.
RE:"Good sources of high resolution reference spectra are UVES POP
https://www.eso.org/sci/observing/tools ... rface.html
and ELODIE 3.1"
I wonder if there is a way to save a star's spetra (let's say Castor) in 1D format
to retrieve into Bass so I can do the division and IR curve on a more "exact" spectra?
Thanks for the info on Sheratan!

James

[Robin Leadbeater]

Hi James,

ISIS has 1D UVES spectra for the H alpha region built into its database so if that is the range you need you could take them from there. If you need other wavelength regions, suitable 1D files can be generated though

I am not a BASS user and UVES files are not simple 1D fits. There may be an easier way but for UVES POP stars

Find the star you want eg Castor from
http://www.eso.org/sci/observing/tools/ ... tonow.html
and click on "plot"
Tick the "ascii file" box, chose the range you want and click "plot"
A link to a txt file will appear. Download this
The format is not directly compatible with ISIS or Vspec as it has an extra "std dev" column so you need to edit it to create the usual 2 column wavelength/flux dat file. Alternatively Vspec will do it for you if you change the file type from txt to uvs and load it into Vspec using "load"
"profile", selecting uvs file type in the drop down box. You can then save it as dat or fit.

The ELODIE 3.1 library is also available in ISIS
http://www.spectro-aras.com/forum/viewt ... t=10#p7224
or alternatively you can use Paolo's spreadsheet to generate 1D fits files for any of the stars.

Cheers
Robin

[Robin Leadbeater]

To get you started here is the UVES Castor spectrum (from 3500-8000A) in 1D fits format. Note that this is a "real" spectrum and still includes telluric lines so if you are working in a region with telluric lines it is a good idea to clean them out of the UVES spectrum first. VSpec and ISIS have a tool for this, not sure about BASS. (Note that the tellurics have been removed in UVES H alpha spectra in the ISIS database.)

Cheers
Robin

EDIT : Hmm... the file seems to have undergone a wavelength shift in the conversion to fits so here is the dat version instead
EDIT: Still a problem so I have removed the attached file while i sort out what has gone wrong

[James Foster]

To: Robin,

Thanks for your efforts!
I have to admit that this spectra accuracy/reduction is mostly beyond my grasp
until I start using the Isis program...which I intend to start learning this spring after
I purchase an Alpy600 (with all accessories) or LHRESIII.

James

[Olivier GARDE]

Hi James,

For good accuracy and good process, ISIS is better than BASS and you have many tutorial on Christian's website dedicated to Alpy, LISA, LHIRES and eShel spectrographs.
http://www.astrosurf.com/buil/isis/isis_en.htm

You have also spcaudace :
http://bmauclaire.free.fr/spcaudace/

And VSpec :
http://www.astrosurf.com/vdesnoux/

[James Foster]

Your right Olivier, but I've been putting-off Isis until
I get a spectroscopic system that included on object flats.
I tried Halogen flats (as seen here: http://www.astrosurf.com/buil/lhires_flat/flat.htm)
but either the light source wasn't "pure" halogen or my CDK optics wouldn't work with
this technique; the spectra with applied flats looks horrifically unevenly illuminated.

As I move over to Alpy600 or LHIRES with a built-in flat system, I'll definitely make the
move to the Isis spectra program.

James