ASTRO: McNeil's Nebula -- Unchanging for now

Some variable nebula vary as various parts of it are lit as clouds
around the illuminating star move around. That is the case with my
previously posted variable nebula, Gyulbudaghian's Nebula, lit by PV
Cephi. In this case however the nebula seems to suddenly appear then
disappear as a whole, along with the star itself, V1647 Orionis. This
would seem to indicate the light traveling to the top of the nebula from
the star then to us travels about the same total distance as light
hitting the bottom of the nebula then coming to us travels. Several
geometries could explain this. Or else no one is looking when it fades
in or out. Still the distances have to be rather close I'd think.

McNeil's Nebula was discovered on January 23, 2004 by the advanced
amateur astronomer Jay McNeil while testing a new 3" refractor on M78.
He noticed a nebula unknown to him or as it turned out to anyone. A
check of survey images prior to his showed no object there. Finally it
was noticed that Evered Kreimer had taken it decades earlier as part of
a book published by Sky and Telescope Magazine of the M objects.
http://www.amazon.com/The-Messier-Al.../dp/0933346042 The
image for M78 that was taken with his f/7, 12" reflector on dry ice
cooled Tri-X film in October of 1966 showed it clearly.
http://messier.seds.org/Pics/More/m78mcneil.jpg But images soon after
were again blank. Since then a few other prediscovery images have been
found taken when it appeared for short periods.

When Jay announced the new nebula I was building my Observatory which
wouldn't be complete with Orion out of the sun's glare until the
following fall. By then it had again vanished. I was bummed out. Not
until 2008 did it reappear. It has remained visible ever since.

Each year since then I've taken an image of it looking for changes but
so far the only changes I can be certain of appear to be due to my
seeing. Every time I try for it seeing is lousy or transparency is bad
or both. Only in 2010 did I get a fairly good image of it. I tried
twice recently, once on December 23rd, 2014 and again in February 2014.
The latter suffered from poor seeing and won't be processed. I'd
hoped to add the two together to get a better image but the latest
attempt is so bad in comparison I gave up that idea. The December image
isn't great but will have to do. I've included a comparison of the
2008, 2010 and now 2013 images. I see color differences due to mostly
conditions. While skies were good for the luminance in 2010 clouds cut
me off for the color data which was therefore weak making for an anemic
color version compared to 2008 and 2013. While I see some changes,
especially at the north end I can't say it has changed over the years.
Will it again vanish or is it here to stay?

This year I did annotate the image as there's a lot going on besides
McNeil's Nebula and M78 partly cut off at the top as I centered on
McNeil's Nebula. Many of the Herbig Haro objects have A, B, C etc.
elements. I didn't annotate them if they were so connected as to appear
to be one object has in the complex, as is the case with HH 24. I've
marked the location of HH22 but the only nebulosity I see there is that
of McNeil's Nebula which is not HH22 best as I can determine. An image
of the area taken between 2004 and 2008 when the nebula had faded away
clearly shows the real HH24 glowing with typical H alpha's pink color.
http://www.eso.org/public/usa/images/eso1105d/ It was completely drown
out by McNeil's Nebula in my image without H alpha data.

As I've tried to find variations in the nebula since its reappearance in
2008 and am yet to find any I will stop making an annual attempt until
it is obvious some change has occured. Note the illuminating star also
comes and goes with the nebula but only in visible light. In IR light
it is always seen.

To illustrate its unchanging status since 2008 I've posted a comparison
from 2008, 2010 and 2013. The 2008 was taken with the best transparency
and worst seeing. 2010 had the best seeing but poorest transparency and
2013 had fair seeing and fair transparency. The only change I can see
with any certainty relate to these conditions.

One bright asteroid also made an appearance. Details are in the
annotated image.

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

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

Rick,

a very detailed view of this tiny nebula.
I'll have to revisit it next winter.

Stefan


"Rick Johnson" schrieb im Newsbeitrag
...

Some variable nebula vary as various parts of it are lit as clouds
around the illuminating star move around. That is the case with my
previously posted variable nebula, Gyulbudaghian's Nebula, lit by PV
Cephi. In this case however the nebula seems to suddenly appear then
disappear as a whole, along with the star itself, V1647 Orionis. This
would seem to indicate the light traveling to the top of the nebula from
the star then to us travels about the same total distance as light
hitting the bottom of the nebula then coming to us travels. Several
geometries could explain this. Or else no one is looking when it fades
in or out. Still the distances have to be rather close I'd think.

McNeil's Nebula was discovered on January 23, 2004 by the advanced
amateur astronomer Jay McNeil while testing a new 3" refractor on M78.
He noticed a nebula unknown to him or as it turned out to anyone. A
check of survey images prior to his showed no object there. Finally it
was noticed that Evered Kreimer had taken it decades earlier as part of
a book published by Sky and Telescope Magazine of the M objects.
http://www.amazon.com/The-Messier-Al.../dp/0933346042 The
image for M78 that was taken with his f/7, 12" reflector on dry ice
cooled Tri-X film in October of 1966 showed it clearly.
http://messier.seds.org/Pics/More/m78mcneil.jpg But images soon after
were again blank. Since then a few other prediscovery images have been
found taken when it appeared for short periods.

When Jay announced the new nebula I was building my Observatory which
wouldn't be complete with Orion out of the sun's glare until the
following fall. By then it had again vanished. I was bummed out. Not
until 2008 did it reappear. It has remained visible ever since.

Each year since then I've taken an image of it looking for changes but
so far the only changes I can be certain of appear to be due to my
seeing. Every time I try for it seeing is lousy or transparency is bad
or both. Only in 2010 did I get a fairly good image of it. I tried
twice recently, once on December 23rd, 2014 and again in February 2014.
The latter suffered from poor seeing and won't be processed. I'd
hoped to add the two together to get a better image but the latest
attempt is so bad in comparison I gave up that idea. The December image
isn't great but will have to do. I've included a comparison of the
2008, 2010 and now 2013 images. I see color differences due to mostly
conditions. While skies were good for the luminance in 2010 clouds cut
me off for the color data which was therefore weak making for an anemic
color version compared to 2008 and 2013. While I see some changes,
especially at the north end I can't say it has changed over the years.
Will it again vanish or is it here to stay?

This year I did annotate the image as there's a lot going on besides
McNeil's Nebula and M78 partly cut off at the top as I centered on
McNeil's Nebula. Many of the Herbig Haro objects have A, B, C etc.
elements. I didn't annotate them if they were so connected as to appear
to be one object has in the complex, as is the case with HH 24. I've
marked the location of HH22 but the only nebulosity I see there is that
of McNeil's Nebula which is not HH22 best as I can determine. An image
of the area taken between 2004 and 2008 when the nebula had faded away
clearly shows the real HH24 glowing with typical H alpha's pink color.
http://www.eso.org/public/usa/images/eso1105d/ It was completely drown
out by McNeil's Nebula in my image without H alpha data.

As I've tried to find variations in the nebula since its reappearance in
2008 and am yet to find any I will stop making an annual attempt until
it is obvious some change has occured. Note the illuminating star also
comes and goes with the nebula but only in visible light. In IR light
it is always seen.

To illustrate its unchanging status since 2008 I've posted a comparison
from 2008, 2010 and 2013. The 2008 was taken with the best transparency
and worst seeing. 2010 had the best seeing but poorest transparency and
2013 had fair seeing and fair transparency. The only change I can see
with any certainty relate to these conditions.

One bright asteroid also made an appearance. Details are in the
annotated image.

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

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