spectro-aras.com

Greetings all,

I'm new to the forums and my college recently purchased an eShel for use on our 0.5m telescope. I've installed everything and all seems to be working nominally, but upon reducing my inaugural spectrum of Vega using ISIS, I noticed something I can't explain. Specifically, the spectrum of Vega shows an increase in intensity towards longer wavelengths. Note the spectrum shown in the picture is not corrected for instrumental response. I'm at a lose to explain this - I'm almost positive that I've reduced the spectrum correctly in ISIS. Can anyone provide me some insight into what's causing the increase in intensity?

Thanks,

James Clem
Grove City College

Dear James,

It is "normal" to obtain such a profile because precisely there is no instrumental response that can correct the spectrum of both:
- the setup response (optical, CCD)
- The height of the target and therefore the air mass

So you can apply the instrumental response on your Vega spectrum using this tutorial :
http://www.astrosurf.com/buil/isis/eshe ... chelle.htm
and
http://www.astrosurf.com/buil/isis/eshel/tuto1.htm
but only in French I think...

And use a A0V star in the ISIS database, you should get the following profile

Hi Oliver,

Thanks for the reply to my question. I understand that I need to determine the instrumental response by comparing my spectrum to an A0V (Vega-like) star. I was just shocked when I saw the Vega spectrum increasing dramatically towards the red end. I'm using an ATIK460EX and thought my response function should peak out around 5000 A or so rather than continue to rise beyond 7000 A. I thought i was making a processing error.

James

By the way... I noticed you are also using an ATIK460EX. Do you operate in binned 2x2 or unbinned for the acquisition of your spectra?

Hi Clem,

The merging of the orders is very good
It is strongly recommanded by Christian Buil to work with bin 1

All the best,

François Teyssier

For binning ? I use both according to the type of target:
- Bin 1x1 for bright target
- Bin 2x2 for weak target