ASTRO: IC 477/2169 -- a large reflection nebula

IC 447/2169 is a reflection nebula but like SH2-235 it has an identity
crisis. The NGC project - now back on line at a new URL,
http://www.ngcicproject.org/, under new ownership but same content by
Dr. Robert E. Erdmann, Jr. - has this to say about the nebula and a
nearby reflection nebula (half degree north and just out of my field)
reflection nebula (IC-446/IC-2167) I haven't as yet imaged. They,
though, are connected by a dark nebula. I need a wide angle scope to
capture this however.

"The same two objects [IC-446/IC-2167, and IC-447/IC-2169] were
apparently discovered twice by Barnard... Neither of Barnard's positions
is particularly good, though we can get close to the apparent center of
his large, diffused nebulosity if we adopt his RA for IC 447 and his Dec
for IC 2169. Even though his two positions are more than 10 arcmin
apart, they clearly refer to the same object: it is big (I make it about
30 x 30 arcmin on the DSS). Barnard notes "several stars 9-10 involved";
those stars are indeed there."

Barnard never realized they were the same object. Though in a later
publication he did retract his discovery of IC 447 saying it was a
duplicate of NGC 2245 -- the cone nebula. Which, of course is
incorrect. He did though send the data on both to Dreyer who did
publish it in his second IC catalog without apparent verification and
likely accepted Barnard's description without viewing it himself. So
even the most careful of visual astronomer's, and Barnard is considered
one of the best, did make mistakes that the later photographic era would
have prevented. Or maybe not considering the SH2-235 problems.

IC 447/2169 (it is also known as Dreyer's Nebula) is located in
Monoceros, the unicorn. So obviously another that has been waiting on
the hard drive for some time. It is thought to be part of the huge
cloud of dust and gas that includes the far more famous emission and
dark nebula known as the Cone Nebula as well as the Christmas Tree open
star cluster and the Fox Fur Nebula. If so it is about 2700 light years
distant, considerably further away than the nearby Orion Nebula complex.

Being a reflection nebula it is a blue color. The color comes from
scattered star light of the illuminating stars which are either in or
behind it. The nebula is blue for the same reason our sky is blue. The
tiny molecules of dust and gas scatter blue light better than the other
colors due to its short wavelength. It matters little what color the
illuminating stars are, as long as they emit some blue light the nebula
was take on a blue color same as the somewhat yellow sun still results
in our blue sky.

I've reproduced this image at 1.5" of arc per pixel as there is little
more to see at its native 1" per pixel. It is an exceedingly faint
nebula and quite an imaging challenge due to its low surface brightness.

14" LX200R @ f/10, L=6x10' binned 2x2 RGB=2x10' binned 3x3, STL=11000XM,
Paramount ME

Rick

--
Correct domain name is arvig and it is net not com. Prefix is correct.
Third character is a zero rather than a capital "Oh".

Rick, thanks for posting, I don't think I have seen this one before. Not an
object I will go for as I usually find reflection nebulae to be the most
difficult class of objects, at least under city skies.

Stefan

"Rick Johnson" schrieb im Newsbeitrag
ster.com...
IC 447/2169 is a reflection nebula but like SH2-235 it has an identity
crisis. The NGC project - now back on line at a new URL,
http://www.ngcicproject.org/, under new ownership but same content by
Dr. Robert E. Erdmann, Jr. - has this to say about the nebula and a
nearby reflection nebula (half degree north and just out of my field)
reflection nebula (IC-446/IC-2167) I haven't as yet imaged. They,
though, are connected by a dark nebula. I need a wide angle scope to
capture this however.

"The same two objects [IC-446/IC-2167, and IC-447/IC-2169] were
apparently discovered twice by Barnard... Neither of Barnard's positions
is particularly good, though we can get close to the apparent center of
his large, diffused nebulosity if we adopt his RA for IC 447 and his Dec
for IC 2169. Even though his two positions are more than 10 arcmin
apart, they clearly refer to the same object: it is big (I make it about
30 x 30 arcmin on the DSS). Barnard notes "several stars 9-10 involved";
those stars are indeed there."

Barnard never realized they were the same object. Though in a later
publication he did retract his discovery of IC 447 saying it was a
duplicate of NGC 2245 -- the cone nebula. Which, of course is
incorrect. He did though send the data on both to Dreyer who did
publish it in his second IC catalog without apparent verification and
likely accepted Barnard's description without viewing it himself. So
even the most careful of visual astronomer's, and Barnard is considered
one of the best, did make mistakes that the later photographic era would
have prevented. Or maybe not considering the SH2-235 problems.

IC 447/2169 (it is also known as Dreyer's Nebula) is located in
Monoceros, the unicorn. So obviously another that has been waiting on
the hard drive for some time. It is thought to be part of the huge
cloud of dust and gas that includes the far more famous emission and
dark nebula known as the Cone Nebula as well as the Christmas Tree open
star cluster and the Fox Fur Nebula. If so it is about 2700 light years
distant, considerably further away than the nearby Orion Nebula complex.

Being a reflection nebula it is a blue color. The color comes from
scattered star light of the illuminating stars which are either in or
behind it. The nebula is blue for the same reason our sky is blue. The
tiny molecules of dust and gas scatter blue light better than the other
colors due to its short wavelength. It matters little what color the
illuminating stars are, as long as they emit some blue light the nebula
was take on a blue color same as the somewhat yellow sun still results
in our blue sky.

I've reproduced this image at 1.5" of arc per pixel as there is little
more to see at its native 1" per pixel. It is an exceedingly faint
nebula and quite an imaging challenge due to its low surface brightness.

14" LX200R @ f/10, L=6x10' binned 2x2 RGB=2x10' binned 3x3, STL=11000XM,
Paramount ME

Rick

--
Correct domain name is arvig and it is net not com. Prefix is correct.
Third character is a zero rather than a capital "Oh".

Rick
I thought you were only on a steady diet of galaxies....
that looks like a target reserved for dark skies

I like it though!
rdc

Richard Crisp wrote:
Rick
I thought you were only on a steady diet of galaxies....
that looks like a target reserved for dark skies

I like it though!
rdc


That whole area would be a great target next fall for your new camera on
the refractor. You could catch the entire area. Would need several
nights of exposure to pick up the dust and dark nebula well however.

Rick

--
Correct domain name is arvig and it is net not com. Prefix is correct.
Third character is a zero rather than a capital "Oh".

"Rick Johnson" wrote in message
ster.com...
Richard Crisp wrote:
Rick
I thought you were only on a steady diet of galaxies....
that looks like a target reserved for dark skies

I like it though!
rdc


That whole area would be a great target next fall for your new camera on
the refractor. You could catch the entire area. Would need several
nights of exposure to pick up the dust and dark nebula well however.



That's a great idea Rick.

i affixed the camera onto my AP155EDF f/7 with the 4" field flattener two
weeks ago.

Of course I got skunked the first night it was ready: clouds....

then every weekend since: clouds...

I figure I will get a somewhat larger FOV but moving from f/9 to f/7 will
nearly double my exposure rate. With the ~20% QE of the new camera that will
be a welcome improvement I think.

The '155 has great star quality too and the 4" field flattener should not
give me any vignetting. The 2.7" flattener I have with the '180EDT f/9 seems
to vignette just a slight amount in the corners

All in all I am looking forward to trying the combination. I have never used
the 4" flattener but acquired it about three years ago in a trade....