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ASTRO: NGC 7048 a planetary nebula



 
 
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  #1  
Old October 11th 12, 06:54 AM posted to alt.binaries.pictures.astro
Rick Johnson[_2_]
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Posts: 3,085
Default ASTRO: NGC 7048 a planetary nebula

NGC 7048 is a rather nice planetary nebula in Cygnus about half way
between M39 and the North American Nebula that I've managed to avoid
imaging until late September 2011. I find several distance estimates
for it indicating how hard it is determine the distances to these
objects. The closest puts it at 1900 light-years away. The most distant
says 8800 light-years while the newest I could find (2004) says 4900
light-years. Flip your three sided coin for the answer. The stars seen
against the nebula are all foreground or background stars except for the
faint blue central star whose UV light is causing the gasses, expelled a
few thousand years ago by the dying star, to glow. It has a surprising
amount of detail in it that, thanks to better than normal seeing, I was
able to bring out. In fact seeing was so good I should have imaged it
at 0.5" per pixel instead of my standard 1" per pixel but since I was
sound asleep while the computer took the data I didn't realize how good
the seeing had become as the night progressed.

The nebula was discovered in 1878, by Jean Marie Edouard Stephan, using
a 31.5-inch reflector. At magnitude 12.1 and about a minute of arc
across it isn't a really bright planetary but should be visible in an 8"
scope under reasonably dark skies.

One source called it the Ornament Nebula. I'd not heard that name
before. It does sort of fit if you like amorphous colored Christmas
tree balls I suppose. Another imager suggested "Alien Nebula" as he
thought he saw a face in it.

Due to all the stars the file size is rather large at nearly 800K. It's
worth looking at the full image as to the upper right is the reflection
nebula (SIMBAD's description) GN 21.11.4. It is weird in that it isn't
mostly around its illuminating star but mostly to one side of it. Also
it isn't blue but a color that to me appears a mix of H alpha and the
color of the illuminating star. However if the illuminating star is the
one in its lower edge it wouldn't have the UV light needed to create H
alpha emission. So the H alpha is likely an illusion. Also it has a
very dark, but not black hole in it. This appears to me due to barely
illuminated dust rather than a true hole in the nebula. A similarly
colored nebula surrounds a nearby star to the northeast. I found no
separate designation for it in SIMBAD. I've included these in the
enlarged, cropped image.

14" LX200R @ f/10, L=4x10' RGB=2x10', STL-11000XM, Paramount ME

Rick
--
Prefix is correct. Domain is arvig dot net

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Name:	NGC7048L4X10RGB2X10DR.JPG
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Name:	NGC7048L4X10RGB2X10DR-CROP150.JPG
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  #2  
Old October 24th 12, 07:50 PM posted to alt.binaries.pictures.astro
Stefan Lilge
external usenet poster
 
Posts: 2,269
Default ASTRO: NGC 7048 a planetary nebula

Beautiful image Rick.
Detail, colour etc look all very good. I even "discovered" the reflection
nebula before I read your description. Nice bonus.

Stefan

"Rick Johnson" schrieb im Newsbeitrag
.com...

NGC 7048 is a rather nice planetary nebula in Cygnus about half way
between M39 and the North American Nebula that I've managed to avoid
imaging until late September 2011. I find several distance estimates
for it indicating how hard it is determine the distances to these
objects. The closest puts it at 1900 light-years away. The most distant
says 8800 light-years while the newest I could find (2004) says 4900
light-years. Flip your three sided coin for the answer. The stars seen
against the nebula are all foreground or background stars except for the
faint blue central star whose UV light is causing the gasses, expelled a
few thousand years ago by the dying star, to glow. It has a surprising
amount of detail in it that, thanks to better than normal seeing, I was
able to bring out. In fact seeing was so good I should have imaged it
at 0.5" per pixel instead of my standard 1" per pixel but since I was
sound asleep while the computer took the data I didn't realize how good
the seeing had become as the night progressed.

The nebula was discovered in 1878, by Jean Marie Edouard Stephan, using
a 31.5-inch reflector. At magnitude 12.1 and about a minute of arc
across it isn't a really bright planetary but should be visible in an 8"
scope under reasonably dark skies.

One source called it the Ornament Nebula. I'd not heard that name
before. It does sort of fit if you like amorphous colored Christmas
tree balls I suppose. Another imager suggested "Alien Nebula" as he
thought he saw a face in it.

Due to all the stars the file size is rather large at nearly 800K. It's
worth looking at the full image as to the upper right is the reflection
nebula (SIMBAD's description) GN 21.11.4. It is weird in that it isn't
mostly around its illuminating star but mostly to one side of it. Also
it isn't blue but a color that to me appears a mix of H alpha and the
color of the illuminating star. However if the illuminating star is the
one in its lower edge it wouldn't have the UV light needed to create H
alpha emission. So the H alpha is likely an illusion. Also it has a
very dark, but not black hole in it. This appears to me due to barely
illuminated dust rather than a true hole in the nebula. A similarly
colored nebula surrounds a nearby star to the northeast. I found no
separate designation for it in SIMBAD. I've included these in the
enlarged, cropped image.

14" LX200R @ f/10, L=4x10' RGB=2x10', STL-11000XM, Paramount ME

Rick
--
Prefix is correct. Domain is arvig dot net

 




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