North Galactic Pole

Not every useful pointing is a bright one.

Why point here. Looking straight out of the Galactic disk, the path length through hydrogen is as short as it gets, so the line is far weaker than anywhere in the plane. Weak is not zero: there is still local gas above and below the Sun. That makes the pole a useful comparison. A spectrum that looks just as strong here as it does in Cygnus is telling you something about your bandpass correction or about local interference, not about the sky.

What you’ll see. A faint line near zero velocity, or nothing at all with a small antenna and a short integration. Use the radiometer equation to work out how long you would need to integrate to see it, then decide whether that’s worth the time. Often the better use is a quick comparison: take the same integration here and in the plane, and check that the difference between them looks like a line.

No velocity model. The rotation model on the other target pages only describes gas in the plane. At b = 90° it doesn’t apply, so this page doesn’t show one.

Practicalities. At +27° declination it rises well from both hemispheres, culminating near 77° from 40° N. It transits at midnight in early April. The South Galactic Pole, in Sculptor, does the same job for southern observers.