NGC 7023 - Iris Nebula
NGC 7023, also known as the Iris Nebula or Caldwell 4, is a reflection nebula containing the open cluster OCL 235 located in the constellation Cepheus, approximately 1 300 light-years from Earth.
This nebula was discovered by the German-British astronomer William Herschel in 1794.
The star illuminating the Iris Nebula is HD 200775, a Herbig-Haro star of spectral type BE. The parallax of this star, measured by the Gaia satellite, is 2.8175 ± 0.0374, which corresponds to a distance of 494 ± 19 pc (approximately 1 610 light-years).
Type B stars are very luminous and hot (Color temperature: 13 000 Kelvin)
Infrared Emission
Several recent publications have focused on the near-infrared and mid-infrared emissions of NGC 7023.
These emissions come from the fluorescence of polycyclic aromatic hydrocarbons (PAHs) and fullerenes (C60) excited by ultraviolet radiation.
Quick Facts
Type : Reflection Nebula
Constellation : Cepheus
Distance : ~1,300 light-years
Size : ~6 light-years across
Apparent Magnitude : 7.0
Central Star : HD 200775 (illuminates the nebula)
What Makes It Special?
Blue glow : The Iris Nebula shines with a beautiful blue hue because of light from the hot, young star HD 200775 being scattered by surrounding dust. This scattering is similar to what makes Earth's sky appear blue.
Dark and light contrast : Surrounding the nebula are dark lanes of dust, making the bright center stand out vividly — a favorite for astrophotographers.
Star formation : The nebula is embedded in a molecular cloud, a region where new stars are being born.
How to See It
Best viewed in August–October from the Northern Hemisphere.
Needs a telescope or good astrophotography setup to observe well due to its dim brightness.
The nebula NGC 7023 is located about 3.3 degrees southwest of the star Beta Cephei and about 5.3 degrees northwest of Alpha Cephei.
Set up
Celestron C8 on Eq6 R Pro mount
ASI533 MC Pro camera for imaging
ASI220 mini camera for guiding via OAG Celstron
Optolong L Quad
Control via ASIAIR PLUS
Gain (ISO) : 101
Camera cooling : -10°C
Preprocessing : Siril
Processing : Pixinsight
The session
NGC 7023 was taken in May 30th.
48 images of 5 minutes each
Total integration : 4 hours
A guiding quite correct
The Final Image
Astrometry : Annotated version
Clear Sky !
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