The shape of your spectrum of the Milky Way, (this one) 
Looks correct. The two peaks near 1420.5 Hz are two different arms of the Milky Way,
so you’re already seeing structure of our Galaxy! Since we, and these spiral arms
are in a disk, we’re seeing one behind the other in intensity, but because they
are moving at different speeds they are separated in frequency.
All the many regularly spaced peaks are interference. There are 9 in 0.5 MHz so roughly
one every 0.05 MHz. This could be due to a single very strong interfering signal
out of band. This could be due to power lines. Try to move away from power lines and
they might go away.
Also using a Software defined radio (SDR) with more bits of sampling (like the AIRSPY mini)
can also partially reduce bad sampling, and clean up the signals.
Glen
On Jul 7, 2020, at 4:09 PM, David Schultz <physicsmandave@gmail.com> wrote:
Hi Glen,
Let's see if this works for the figures. 3 attached.
Dave
<Mirfak2-grastro.jpg><Mirfak-Myprogram.jpg><my_flowgraph.png>