From: "Stanford, Darryl" <stanfordd@smccd.edu>
Date: April 23, 2011 4:12:01 PM MDT
To: "Astro_IIDC@yahoogroups.com" <Astro_IIDC@yahoogroups.com>
Cc: "Stanford, Darryl" <stanfordd@smccd.edu>
Subject: Re: [Astro_IIDC] Re: Spectroscopy
Hi Milton,
I just used IRAF. It has routines for deconvolving the spectrum your are recording with a selected standard star spectrum. Adding in a library to Astro IIDC would probably be needed. I believe that Tom Field in Rspec uses the Pickles Atlas:
A STELLAR SPECTRAL FLUX LIBRARY BY A.J. PICKLES (1998) (PASP 110, 863)
Darryl
On 4/23/11 12:17 PM, "Milton Aupperle" <milton@outcastsoft.com> wrote:
Hi Darryl;
On 23-Apr-11, at 12:31 PM, Stanford, Darryl wrote:
-------- Snipped for Brevity.
>
> Terrance and Milton,
> Our observatory is using students, in a special projects class, to
> help take dozens of spectra of the eclipsing binary epsilon Aurigae,
> using an off-the-shelf Meade 8”, an SBIG SGS spectrograph and
> CCDSoft. We have taken darks but have not needed to take flats in
> any of our spectra. We are also beginning to make our own spectral
> catalog to use in my labs. We are in an urban environment in San
> Mateo and find that light pollution is not a problem, even with the
> glow of San Francisco city lights 25 miles away and parking lot
> lights on campus. The spectral quality has been sufficiently good,
> such that students have presented several posters at recent AAS
> meetings. The point that I am making is that small telescopes can
> do amazing work in spectroscopy, as part of a community college
> curriculum.
If your not taking Flats, are you calibrating your profiles / curves
for the camera with a known star spectral profile? Or are you just
using Raw curves for your program work?
I'm just trying to figure out what people are likely to do, so that
I'm not spending too much time adding features people won't use
anyhow. Adding in the absolute calibration stuff is a considerable
amount of work (i.e. smoothing curves, re-sampling curves to a common
base values, setting up file formats, managing file curves etc.) over
the basic features.
Flats may or may not be needed, depending on your optical system,
though they are recommended by other peoples work flow. With my ATRC8
scope, I have at most 0.7% brightness difference across the 1384 x
1036 2/3" Grasshopper CCD FOV (I measure these things). You get bigger
difference for changing elevation and star air masses than that. With
the C8 and a Focal reducer at F5.7, my variance was was much higher
across the field.
But if you have any "donuts" (i.e. dust on the CCD, dust on your
filters etc.) , you do want to make sure those get corrected out or
they affect your spectral curve. If your optical system produces an
evenly illuminated field, then a single set of flats to remove dust
donuts for the camera and filters would do the job fine. Your likely
not going to be doing log sqrt curve stretches on spectra or it screws
up your absolute spectral curves.
One feature that likely would be includes is subtracting the spectral
continuum curve out , which just leaves you with a roughly horizontal
lines that has spiked and dips for emission or absorption lines.
On a related note, if people who are not doing Astronomical imaging
but are doing some sort of spectral work in a different field
(microscopy for example), I'd like to hear from you people too -
either on list or directly at support@outcastsoft.com.
Thanks in advance..
Milton J. Aupperle
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