NEBULAE
The Amazing Clouds of Orion
— IC 434, LDN 1622, Messier 42, Messier 78, Sh 2-276 —
Processed by Nicolas Rolland, Terry Hancock and Tom Masterson. 33.1 hours gathered by Grand Mesa Observatory at Whitewater, Colorado, USA.
Twenty-odd objects in this frame carry their own catalogue numbers. Underneath all of them there is one cloud.
Three panels that became twelve
The project began as a three-panel mosaic covering the Great Nebula in Orion, the Horsehead, Barnard's Loop and Messier 78. It kept growing. The finished mosaic runs to twelve panels and covers 13.5 by 6.8 degrees — a stretch of sky wider than twenty-five full Moons laid end to end — taking in more than twenty deep-sky objects and most of the Orion Molecular Cloud. At full resolution it samples 1.99 arcseconds per pixel and comes to 1.8 gigabytes, which can be browsed here.
One cloud, twenty names
The Great Nebula, the Horsehead, the Flame, Messier 78, Barnard's Loop, LDN 1622, Sh2-276 — they were catalogued separately, over three centuries, by observers working through eyepieces that showed a degree or two at a time. Each was the brightest thing in its own small field, so each got a name. They are all the same cloud: a single structure of gas and dust about 1,400 light-years away, lit in different places by different stars, and dark everywhere else. Seeing it whole is a recent possibility, and it takes a frame this wide.
The hunter, and the swordsman of the sky
Orion dominates the sky from December through March, and it is among the oldest constellations anyone has written down. The Greeks read these stars as a hunter with a belt and a sword, a shield held westward in his left hand and a club raised in his right. J.R.R. Tolkien put them in his own world under the name Menelvagor, the Swordsman of the Sky.
Thirty-three hours in three regimes
A Takahashi E-180 astrograph with a full-frame colour sensor, from Whitewater in January 2022 — thirty-three hours in total, and not one exposure but three. The wide clouds were built from two-minute frames and from ten-minute H-alpha, which is what the faint dust between the nebulae needs. The Horsehead had its own set. And Messier 42 had a third, because the Trapezium is bright enough to saturate in seconds: alongside the two-minute frames there are exposures of one second, taken for no other reason than to hold four stars that everything else in this field burns out. A mosaic this wide is not a matter of pointing at more sky. It is a matter of the brightest thing and the faintest thing being fifteen magnitudes apart and both having to appear.
This image is a collaborative project between Terry Hancock, Tom Masterson and Nicolas Rolland.
