NGC 6888

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Observation place
New Mexico


TelescopeTakahashi Epsilon 250 - 10 ″, 850mm FL @ f / 3.4
MountParamount ME
Imaging cameraSBIG ST10XME - Non Anti Bloomin Gate (NABG) regulated at -10o Celsius
Image typeHa (RGB)
ExhibitionHa (10 x 5 'bin 1 × 1), RGB (4 x 2' bin 2 × 2 each)
PretreatmentMaxim DL
TreatmentPhotoshop and PixInsight

Object description

Object type“The Crescent Nebula” emission nebula
Visual magnitudeMore than 10 (varies according to references)
Distance5000 light years
Diameter3 light years
Dimension seen from Earth20 x 10 arc minutes
The Crescent Nebula is very difficult to photograph because it has a magnitude over 10. There are a lot of very pale gaseous components. Looking at the photo, you can see some of these very pale ramifications. Some astrographers manage to show even more, especially by using specialized filters to bring out these pale components in their light spectrum (especially the blue color which is hardly visible in the image). Here, the H-Alpha filter does a good job of bringing out the pale components of the nebula in the red light spectrum (hydrogen component). In addition, a vast cloud of very faint red-colored gas surrounds this nebula. It can be seen in this photo, especially towards the bottom of the nebula.  

The central star of the Crescent Nebula is a Wolf-Rayet star. About 4,5 million years after its formation (one thousandth the age of the Sun), this massive star became a red giant and expelled its outer layers at a speed of about 35 km/h. 000 years later, the intense radiation from its very hot inner layer, exposed, began to project gas at more than 200000 million km / h. This strong stellar wind ejected a solar mass's worth of material every 4,5 years, forming the series of dense concentric shells seen in the image. Radiation from the hot central star, as in all emission nebulae, excites stellar matter, mostly hydrogen, and causes it to glow in the red part of the spectrum. This central star should explode in a supernova within 10 years.
Richard Beauregard
Sky Astro - CCD
My impression "We cannot be alone in this gigantic universe"