Heart Nebula
"They wonder how long I’ll last, how long I’ve been burning. And they never see how brief their existence is in the expanse of this glow. I’ve seen planets born and die in the blink of a cosmic eye."
“How to Photograph a Beating Heart 7 500 Light-Years Away”
On the night of 21 October 2024, the Moon—fat and dazzling at 89 %—flooded the yard with milk-white light.
But in Cassiopeia a cosmic Valentine was rising, and new Antlia 3 nm filters were itching for a trial. At 20:30 the CGEM mount whispered eastward, an 80 mm refractor in tow, and an unattended session began.
Heartbeat of a Nebula
Name: Heart Nebula (IC 1805, a.k.a. Sharpless 2-190, the “Running Dog”)
What & where: A 150′-wide glow of hydrogen, oxygen, and sulfur gas in the Perseus spiral arm—about four times the diameter of the full Moon.
Engine: Deep inside lies the young star cluster Melotte 15; its hot O-type suns blow fierce winds that carve cavities and light the Heart’s crimson arteries and teal veins.
William Herschel first noted the cloud in 1787, but only modern narrowband imaging reveals its full bouquet of colours.
Two Dozen Gigabytes of Moon-Washed Light
H-α (green) 36 × 300 s 3.0
O III (blue) 9 × 600 s 1.5
S II (red) 9 × 600 s 1.5
Total integration 6.0 h
Camera cooled to –10 °C • Guiding rock-steady at 0.52″ RMS despite 18 km h⁻¹ gusts and 17 °C air. All 54 light frames were sharp—zero rejects—so by dawn computer held 260 files / 22.6 GB of pristine data.
Turning Data into Art
Calibrate with 30 flats, 30 darks, 30 flat-darks per channel—amp-glow tamed before it could creep in.
Stack & stretch each channel in PixInsight; the 3 nm bandwidth sliced clean through moonlight and city glow.
SHO mapping: sulfur → gold, hydrogen → emerald, oxygen → sapphire.
Taming the magenta: after NarrowBandNormalization, stubborn pink stars lingered; an image inversion + SCNR pass siphoned them away—part science, part finger-painting.
Final polish: stars gently muted so the nebula’s looping filaments—like auroras frozen in space—could take center stage.
What the Image Whispers
Big breath: those dark cavities aren’t holes; they’re pockets where stellar winds have blasted out material, leaving glowing walls behind.
Living colour: the orange edges trace sulfur-rich shock fronts; teal wisps show oxygen zones where gas is doubly ionised by the hottest stars.
Moonlight? No worry: with 3 nm filters, even an 89 % Moon is just another streetlamp to ignore.
By 03:00 the script parked the scope; the Heart faded west, and the Moon surrendered to dawn.
On-screen a vast, glowing cardiac muscle still pulsed—a reminder that, given the right tools and a dash of stubbornness, you can catch the Milky Way’s heartbeat even under floodlights.