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The Witch Head Nebula captured by LI FANG using QHY128C
2019 / 03 / 15

The Witch Head Nebula captured by LI FANG using QHY128C. This image was awarded the Image of the Day on Astrobin on Feb 2, 2019.
Technical information:
Imaging camera: QHY128C
Imaging telescope: Takahasahi ε-130d
Mount: iOptron CEM60
Guiding camera: QHY5iim
Date: Dec. 7, 2018
Frames: 90x600"
Integration: 15.0 hours
More formally known as IC2118, the Witch Head Nebula is a reflection nebula 1000 light-years away which glows primarily by light reflected from the supergiant star Rigel of the constellation Orion.

Rigel, the seventh-brightest star in the night sky located at the Orion’s foot.
Attribution: Orion_constellation_map.png” by Torsten Bronger, licensed under CC BY 2.0
Fine dust in the nebula reflects starlight. The blue colour of IC2118 is caused not only by Rigel's blue colour but because the dust grains reflect blue light more efficiently than red. The same physical process causes Earth's daytime sky to appear blue, although the scatterers in Earth's atmosphere are molecules of nitrogen and oxygen.

Attribution: © Hyperphysics Concepts,
IC2118 is believed to be an ancient supernova remnant or gas cloud. Radio observations show substantial carbon monoxide emission throughout parts of it, an indicator of the presence of molecular clouds and star formation in the nebula.
The molecular clouds of IC2118 are probably juxtaposed to the outer boundaries of the vast Orion-Eridanus bubble, a giant supershell of molecular hydrogen blown by the high mass stars of the Orion OB1 association. As the supershell expands into the interstellar medium, favourable circumstances for star formation occur. IC2118 is located in one such area. The windblown appearance and cometary shape of the bright reflection nebula are highly suggestive of a strong association with the high mass luminous stars of Orion OB1. The fact that the heads of the cometary clouds of IC2118 point northeast towards the association is strong support of that relationship.

The camera used by the author, QHY128C, is one of the top performing cameras in the COLDMOS line designed and manufactured by QHYCCD. It uses the full-frame Sony Exmor IMX128 sensor which is also used in the Nikon D600 DSLR.
With low (1e- to 4e-) readout noise, 5.97um pixels, 74ke- full well capacity and true RAW 14-bit output, QHY128C has a dynamic range of more than 14 stops. It is one of the few cameras with zero amplifier glow thanks to QHYCCD’s anti-amp glow technology.

In terms of dark current noise, QHYCCD implements proprietary technology in hardware to control it in the QHY128C. As a result, the dark current of this camera is a remarkable 0.0006e-/p/s at -15°C, the lowest dark current of any camera in the COLDMOS line.
Halos around bright stars when doing deep sky astrophotography can sometimes be a tricky problem to overcome. However, this can be greatly mitigated by QHY128C’s high-quality AR+AR multi-layer coatings. In addition, the optic window has no built-in IR blocking so its performance at H-alpha and near infrared can be maximized.
QHY128C can also be used very conveniently on DSLR lenses with QHYCCD’s wide range of mechanical adapters for customers wishing to do this. Just like other QHYCCD cameras, QHY128C has effective anti-dew technology and 128MB DDRII buffer to improve data transfer stability.
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