240804 - IC 4592 "Blue Horsehead" nebula
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click image to enlarge
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ASTRO:
type=Reflection Nebula const=Scorpio mag=4 (ν Scorpii) dist~1200 ly size~80 ly IMAGE: location=EB Driveway BrtlCls=4 moon=0.3% (new) exposure=CMOS OSC: 71x180s (3.6h), G100 EQUIPMENT: camera=ZWO ASI2600MC-Pro optics=Nikkor 70-300mm zoom lens, FL=250mm, f/5.3 filter=Optolong L-Pro LPS mount=Celestron AVX guiding=(none) SOFTWARE: acquisition=Stellarium, APT processing=PixInsight (RCAstro) (SetiAstro), Photoshop (Lumenzia), LrC |
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This image doesn't present the famous Horsehead nebula found in our wintertime skies toward the constellation Orion, but rather a fainter nebula that only takes on a familiar form when wide-field imaging equipment is used. The main part of this summer-time molecular cloud complex is reflection nebula IC 4592, known as the “Blue Horsehead”.
Reflection nebulae are made up of very fine dust particles that normally appear dark but can look very blue when reflecting the visible light of nearby hot, energetic stars. In this case, the source of reflected light is a star at the ‘eye’ of the horse. That star is catalogued as ν Sco (Nu Scorpii), where ν (Nu) is the 13th letter of the Greek alphabet, representing the 13th brightest star system inside the IAU recognized boundary of the constellation Scorpio. This star is also identified with the IAU recognized common name, "Jabbah".
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The Blue Horsehead was discovered in 1895 by American astronomer Edward E. Barnard in a photograph he made with the 6" Willard lens at Lick Observatory near San Jose, CA. Then later, in 1946 Swedish astronomer Sven Cederblad published a study of diffuse galactic nebulae where he listed it as number 128 (Cederblad 128, or Ced 128). Then in 1966, Canadian astronomer Sidney van den Bergh searched the photo plates of the Palomar Observatory Sky Survey (POSS) and identified a weak, moderately blue reflection nebula with radius of 5.7 arcminutes surrounding star BD -19°4333 (Jabbah). The outer region of the nebula is a darker red-ish color due to reflected light from α Sco (Antares) located above and to the right, outside this frame.
Jabbah is a septuple star system (7 stars) all of whom appear to be caught in a mutually common gravitational system. The individual stars cannot be resolved by the naked unaided eye, but can be distinguished with the use of a large, long focal length telescope. Together, they have a combined visual brightness of 4.1 magnitude and spectral type B2V; although individually, they differ from one another significantly in visual magnitudes and spectral types. The system's distance is appx 470 light years from Earth. It is one of only two (2) such known systems, the other being AR Cassiopeiae. Higher-multiplicity star systems are uncommon because they are less stable than their simpler counterparts, and often decay (split) into smaller systems.
The Blue Horsehead is too faint to visualize in unaided, open-eye observations, but makes for a beautiful starscape when captured with modest amateur photographic equipment. It is a rarely photographed object; perhaps because its next-door neighbor - the spectacular Rho Ophiuchi molecular cloud complex - tends to draw more attention. In this image, the field-of-view is maximized thru the use of a common camera lens having a relatively short focal length. Many astrophotographers will use equipment supporting shorter focal lengths to achieve a wider field-of-view to enable the capture of more of the molecular cloud around the object. But as is so often the case in artistic astrophotography, trade-offs must be considered when choosing a combination of focal-length and field-of-view. Along with the wider field-of-view comes a loss of detail.
Nonetheless, the Blue Horsehead is a very beautiful capture for amateur astrophotographers seeking to hone and improve their skills.
Reflection nebulae are made up of very fine dust particles that normally appear dark but can look very blue when reflecting the visible light of nearby hot, energetic stars. In this case, the source of reflected light is a star at the ‘eye’ of the horse. That star is catalogued as ν Sco (Nu Scorpii), where ν (Nu) is the 13th letter of the Greek alphabet, representing the 13th brightest star system inside the IAU recognized boundary of the constellation Scorpio. This star is also identified with the IAU recognized common name, "Jabbah".
.
The Blue Horsehead was discovered in 1895 by American astronomer Edward E. Barnard in a photograph he made with the 6" Willard lens at Lick Observatory near San Jose, CA. Then later, in 1946 Swedish astronomer Sven Cederblad published a study of diffuse galactic nebulae where he listed it as number 128 (Cederblad 128, or Ced 128). Then in 1966, Canadian astronomer Sidney van den Bergh searched the photo plates of the Palomar Observatory Sky Survey (POSS) and identified a weak, moderately blue reflection nebula with radius of 5.7 arcminutes surrounding star BD -19°4333 (Jabbah). The outer region of the nebula is a darker red-ish color due to reflected light from α Sco (Antares) located above and to the right, outside this frame.
Jabbah is a septuple star system (7 stars) all of whom appear to be caught in a mutually common gravitational system. The individual stars cannot be resolved by the naked unaided eye, but can be distinguished with the use of a large, long focal length telescope. Together, they have a combined visual brightness of 4.1 magnitude and spectral type B2V; although individually, they differ from one another significantly in visual magnitudes and spectral types. The system's distance is appx 470 light years from Earth. It is one of only two (2) such known systems, the other being AR Cassiopeiae. Higher-multiplicity star systems are uncommon because they are less stable than their simpler counterparts, and often decay (split) into smaller systems.
The Blue Horsehead is too faint to visualize in unaided, open-eye observations, but makes for a beautiful starscape when captured with modest amateur photographic equipment. It is a rarely photographed object; perhaps because its next-door neighbor - the spectacular Rho Ophiuchi molecular cloud complex - tends to draw more attention. In this image, the field-of-view is maximized thru the use of a common camera lens having a relatively short focal length. Many astrophotographers will use equipment supporting shorter focal lengths to achieve a wider field-of-view to enable the capture of more of the molecular cloud around the object. But as is so often the case in artistic astrophotography, trade-offs must be considered when choosing a combination of focal-length and field-of-view. Along with the wider field-of-view comes a loss of detail.
Nonetheless, the Blue Horsehead is a very beautiful capture for amateur astrophotographers seeking to hone and improve their skills.