Alpy 600 - user guide
This response curve is very embossed.
This is different from what you saw on the Sun,
without the flat correction, all the flat field details
were smoothed.
Save the profile, and re-run the data reduction pro-
cess, including the response file name (in “2. General”
tab).
Now the result is only the star profile:
You have now finished the data reduction for your
reference star, and you now have the dispersion law
and the response curve - these data will be reused for
all the stars you observed during the night. For the
other stars, you need run the data reduction process
only once.
However, you must pay special attention to an im-
portant point. You’re working in slitless mode, and
there is no way to put the next star exactly in the
same position as your reference star spectrum. There
will necessarily be a shift between the reference star
and the new target. The dispersion law remains the
same, but it must be shifted to match the new star
position. To do it, you need to identify one line in the
new spectrum, and give its wavelength to ISIS.
For instance, here is a spectrum of 38 Lyn, another
hot star. In the 2D image, you can easily identify the
Balmer line at 4861 Å. Measure its position, and enter
it in the ISIS field at the “3. Calibration” tab:
Run the process, and get the fully processed spec-
trum:
Continue with the same process for all the stars you
observed during the night. Here is an other example,
mu Leo which is K2III:
and a last one, Betelgeuse (M2I type):
You may observe that there are some shifts
in the calibration law from one star to the
other, despite the realignement you made using
a known line. This is due to the fact that the dis-
persion law can be dependent on the spectrum
position in the image. To minimize this effect,
always put the spectrum exactly at the same po-
sition in the image.
You now know how to proceed with a complete and
precise data reduction. With experience, you’ll do this
process in a few minutes for the reference star, and in
a few seconds for all the stars of the night.
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Summary of Contents for Alpy 600
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