ASTRO: NGC 6911

NGC 6911 is a very strange spiral galaxy in eastern Draco about 105
light-years distant by redshift and other methods. It has a drawn out
eastern arm and nothing much in the way of an arm on the other side
other than the ring the one arm comes off of. Instead there's a
disorganized puff of stars where the other arm would be. This is a very
lonely galaxy with no others in the field. NED came up empty looking
for a related galaxy even far outside my field. So how did it get so
screwed up. Is it the product of a merger? I found virtually nothing
on this galaxy in the literature. NED has no redshift data on anything
else in the image and only a half dozen or so other galaxies are even
listed. Those lack even a magnitude reading.

Located far to the north it isn't surprising to find the field full if
galactic cirrus, aka IFN. This is dust well above the plane of the
galaxy reflecting and sometimes emitting light due to the illumination
of the stars of our galaxy below rather than by an individual star as is
the case with most reflection or emission nebulae. Unfortunately August
turned out to start off as poorly as July with horrid transparency.
While the image uses 7 luminance frames I took 16 over three nights to
get the 7 I used. They likely have fewer photons than 2 normal frames
would. The color data was taken the second and third night with 4
frames each color each night of which one each night was usable. Though
I doubt there's even 10 minutes worth of signal in all 8 of each color
and only slightly less in the 2 of each I used. So this one is highly
suspect as to color. There wasn't anywhere near enough color to pick up
the IFN so it is not colored at all. The galaxy is surprisingly red. I
think it likely due to dust reddening as it is near the edge of the
Milky Way. The "bright" star in the upper right corner is a G3V star so
nearly white and that is how it came out indicating the color is likely
correct. The blue tinge is normal due to chromatic issues with the
corrector lens of the scope which is not color corrected and thus can
show this blue tinge on very bright stars.

Again this is an object I can't find posted anyplace on the net in
color. At least not under the NGC 6911 name. Nor did I note in my
notes why it was on my list other than the notation "IFN?" beside it so
somehow I suspected it was there. It is hinted at in the POSS plates so
that might be why the note.

14" LX200R @ f/10, L=7x10' (equal to about 2x10' on a good night)
RGB=2x10' (more like 1x2' on a good night), STL-11000XM, Paramount ME

Why do I continue to process these severely damaged files?

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

Rick,

I wonder if Arp had a "lost arm" category in his catalogue :-)
Lots of detail in this small galaxy, still a shame that you had to throw
away so much data. Could habe done two objects in the same time with better
transparency.

Stefan

"Rick Johnson" schrieb im Newsbeitrag
...

NGC 6911 is a very strange spiral galaxy in eastern Draco about 105
light-years distant by redshift and other methods. It has a drawn out
eastern arm and nothing much in the way of an arm on the other side
other than the ring the one arm comes off of. Instead there's a
disorganized puff of stars where the other arm would be. This is a very
lonely galaxy with no others in the field. NED came up empty looking
for a related galaxy even far outside my field. So how did it get so
screwed up. Is it the product of a merger? I found virtually nothing
on this galaxy in the literature. NED has no redshift data on anything
else in the image and only a half dozen or so other galaxies are even
listed. Those lack even a magnitude reading.

Located far to the north it isn't surprising to find the field full if
galactic cirrus, aka IFN. This is dust well above the plane of the
galaxy reflecting and sometimes emitting light due to the illumination
of the stars of our galaxy below rather than by an individual star as is
the case with most reflection or emission nebulae. Unfortunately August
turned out to start off as poorly as July with horrid transparency.
While the image uses 7 luminance frames I took 16 over three nights to
get the 7 I used. They likely have fewer photons than 2 normal frames
would. The color data was taken the second and third night with 4
frames each color each night of which one each night was usable. Though
I doubt there's even 10 minutes worth of signal in all 8 of each color
and only slightly less in the 2 of each I used. So this one is highly
suspect as to color. There wasn't anywhere near enough color to pick up
the IFN so it is not colored at all. The galaxy is surprisingly red. I
think it likely due to dust reddening as it is near the edge of the
Milky Way. The "bright" star in the upper right corner is a G3V star so
nearly white and that is how it came out indicating the color is likely
correct. The blue tinge is normal due to chromatic issues with the
corrector lens of the scope which is not color corrected and thus can
show this blue tinge on very bright stars.

Again this is an object I can't find posted anyplace on the net in
color. At least not under the NGC 6911 name. Nor did I note in my
notes why it was on my list other than the notation "IFN?" beside it so
somehow I suspected it was there. It is hinted at in the POSS plates so
that might be why the note.

14" LX200R @ f/10, L=7x10' (equal to about 2x10' on a good night)
RGB=2x10' (more like 1x2' on a good night), STL-11000XM, Paramount ME

Why do I continue to process these severely damaged files?

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