THE IRIS NEBULA
LBN 487 / NGC 7023 • Reflection nebula • Cepheus • 1300 light-years from Earth
🔭
Askar 130PHQ
📷
ZWO 2600MC Pro
🌃
Bortle 8
⏱️
30 hours
🗓️
July – August 2024
Overview
The Iris Nebula is a reflection nebula, a cloud of gas and dust that shines by reflecting the light of a nearby star rather than emitting its own. It spans around six light years across and lies roughly 1300 light years from Earth in the constellation Cepheus. The nebula itself is catalogued as LBN 487, while the young stars embedded within and around it form the cluster NGC 7023, which provides the illumination that gives the Iris its distinctive blue glow.
Background
The Iris Nebula is one of the first targets I tackled seriously, back in 2021 using my Askar FRA400 telescope (scroll down to see the pic). It showed me that astrophotography from a city is perfectly achievable with the right approach. Since upgrading to an Askar 130PHQ I’ve been keen to have another crack at the target, using the bigger telescope, Optolong L-Quad Enhance filter, and new processing tools that are available in PixInsight.
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Science
The Iris Nebula appears blue because its central star shines on surrounding dust, and the tiny dust grains scatter shorter-wavelength light (blue) more efficiently than red light. This is the same principle that makes Earth’s sky look blue: molecules in our atmosphere scatter sunlight, favouring blue wavelengths and giving the daytime sky its colour. I’ve made a version without all the foreground stars, to really show off the colour and structure of the nebula:
Kit list
This is the equipment I used to capture the image.
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Telescope: Askar 130PHQ
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Camera: ZWO ASI 2600MC Pro
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Mount: Sky-Watcher EQ6-R Pro
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Guidescope: William Optics 50mm with ROTO Lock
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Guidecam: ZWO ASI 120MM Mini
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Control: ASIAIR Plus
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Filter: Optolong L-Quad Enhance
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Processing walkthrough
Imaging this during the summer, I was prepared for it to be a long-haul — the short nights here in the UK limit the number of the hours you can get in on any given night. In the end I spent six weeks on it, which netted me 30 hours of good quality data.
WBPP in PixInsight is nice and speedy since I upgraded my PC and switched to 5-minute subframes instead of 2-minute (resulting in fewer files that go into the integration pot).
The resulting integrated image showed promise, and some careful editing brought out more detail in the Iris itself, as well as the surrounding dust clouds, than I’d managed before. I’m taking that as a win!
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Example source data
Here are example single subframes and freshly integrated stacks, just with simple stretches applied.
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