Finally a completed Vega Spectrum

[johnb]

So finally using my SA100, QHY5 and Skywatcher

I have a decent Vega spectrum which has been calibrated, instrument corrected and flattened.

Software used was RSpec for calibration and Specta ( http://www.thewhightstuff.co.uk) to determine the temperature in K

The instrument response was the challenging element as I had to ensure it matched the range of the QHY5 which starts at 3800a

Any pointers for further improvement appreciated

Thanks for looking.

Regards

John B

[Merlin66]

John,

Promising result.....

Before normalising, you need to re-validate your instrument response.

Look at the region between the Hb and Ha lines - you show a series of "waves" - four of them....

These should have disappeared when you applied the instrument response correction.

I think you may have "over-smoothed" the correction curve.

Onwards and upwards.

[johnb]

 I think you may have "over-smoothed" the correction curve.

Thanks, I will keep trying, I use the process from this video : http://www.rspec-astro.com/more-videos/  No 15

This has a two stage process so im not 100% sure at which point I over smoothed ?

John B

[johnb]

So after more IR curve experimenting I have the following

Vega IR Corrected, the waves have now gone - although the spectrum is displayed differently, i checked against a reference file and it lines up a treat

and a flattened version again it looks better

Thanks for looking and further advice always appreciated.

John B

[robin_astro]

Hi John,

Your last instrument response corrected profile shape (before normalising) looks good but there are some artifacts around each Balmer  line (emission peaks each side of the absorption lines)

They are probably because you left behind some of the remaining line features which are left in the instrument response after doing the division but should be removed before doing the final smoothing  (These are due to differences in resolution between your measured spectrum and the one from the library.)  

What does you instrument response look like? It should have the waves in it (I suspect caused by the response of the CMOS sensor in the QHY5 camera  as other QHY5 users also see them) but nothing at the Balmer or Telluric line locations.  See here in slides 39-40 for an example of the artifact removal and smoothing stages when producing the instrument response

 http://www.threehillsobservatory.co.uk/astro/Spectroscopy_BAA_VSS_workshop_2008.pdf

Also where have  all those nice short wavelength Balmer lines which were in the original gone?  It should be possible to extend your instrument response far enough into the blue to include these, though you need to take extra care getting a good shape for the instrument response in this region where the response is low.

Cheers

Robin

[johnb]

Thanks for the feedback, thought I had cracked it, getting closer I feel.

do you do skype 

John B

[robin_astro]

See here in slides 39-40 for an example of the artifact removal and smoothing stages when producing the instrument response

 http://www.threehillsobservatory.co.uk/astro/Spectroscopy_BAA_VSS_workshop_2008.pdf

Here is perhaps a better example showing how to crop out the division artifacts before doing a light smoothing to preserve the camera response waves.

blue is the raw division. First the red areas (residual traces of the Balmer lines and the Telluric lines not removed in the division) are cropped out

Then  the result is slightly smoothed to produce the final instrument response

Robin