Hi Steven,
Quote:
Originally Posted by sjastro
The spectrum of Vega using a typical amateur CCD with zero response below 300nm on the other hand does resemble a blackbody.
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Not it does not. It only resembles a black body (though not matching Teff) above the Balmer jump at 3650A but diverges significantly below this as is clear in many amateur spectra eg the first one here which is the same exercise but with a slit spectrograph
http://www.threehillsobservatory.co....ence_stars.pdf
Working below ~3800A with slitless systems like the Star Analyser though is difficult due to the very low signal levels relative to the background.
Quote:
Slide 31 is a good illustration of the issue I described in a previous post.
In the instrument corrected spectrum there is now a wealth of detail below 4200 A which is not in the raw data.
This doesn't look right to me and resembles processing artefacts.
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No this is all good data. (The Balmer series which eventually blend together at the low resolution). If you look at the next slide 32 which compares the measured and library versions (The acid test for a good instrument response which I mentioned in my previous post) you can see good correspondence all the way down to 3800A. The Balmer lines in this region are not obvious in the raw spectrum because they lie on a steep downward slope of the instrument response so just appear as inflections.
RSpec is mainly for beginners and is not the best software for precision work (I use ISIS, sometimes combined with Visual Spec) The technique is tried and tested though and with the pointers in my post can produce a good instrument response with your equipment down to 3800A.
Cheers
Robin