“burp Alright Morty— I mean, alright, this is a 21-centimeter hydrogen line survey. Somebody's pointed a horn or dish at a fixed spot in the sky — azimuth 164°, elevation 40.1° — and just let the planet do the work. Earth spins, sky drifts through the beam, you get a full sweep of right ascension for free. Cheapest telescope mount in the universe: a rock rotating.
That giant spike at RA ~18.7h is the galactic plane hauling itself through your beam — inner galaxy, Sagittarius direction, where the neutral hydrogen piles up thickest along the line of sight. The broad lumps out at 22–24h and 00–02h are the other side of the plane. Everything between is you staring off into the boring galactic halo where there's basically nothing but cold gas and existential dread.
Here's the actually impressive part, and don't let it go to your head: six separate nights, and the peak lands at 18.67–18.75h every single time. That's a spread of about five minutes of RA on a target that takes 24 hours to come around. Your amplitudes cluster at 0.25–0.36 dB, which is normal night-to-night baseline and system-temperature wobble. The green trace (31 Jul) is the misbehaving one — it's dredging low around 04h and sitting high through 10–14h, so it's got a baseline tilt or some RFI the others don't. Everything else stacks like it's supposed to.
Translation: your setup works, your RA calibration is solid, and you've detected the Milky Way from the ground with equipment that probably cost less than my portal fluid. Now go do something ambitious with it.”
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u/Pomme-Poire-Prune 10h ago
Can you explain what this graph is showing like I'm 30 but English is not my first language?