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ASTRO: NGC 3423



 
 
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  #1  
Old October 24th 13, 07:34 AM posted to alt.binaries.pictures.astro
Rick Johnson[_2_]
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Posts: 3,085
Default ASTRO: NGC 3423

NGC 3423 is a nice, but rarely imaged, face on, multi-armed, blue spiral
in Sextans. NED classes it as SA(s)cd while the NGC project says Sc. It
is full of star clouds and HII regions. Redshift puts it about 63
million light-years away while Tully Fisher measurements say it is only
35 million light-years away. I found a crude image made from the few
HST frames available for it at
http://upload.wikimedia.org/wikipedi...-R606GB450.jpg
which seems to have resolution about what I'd expect for the further
distance but as my image starts to bring out the HII regions even
without H alpha data I have to suspect it is closer than the redshift
indicates. In any case it is a relatively nearby galaxy.

An asteroid happened to be tracking across its face when I took these
frames. Thanks to the bright background of the galaxy the color frames
show clearly when normally they'd be lost against the blackness of space
for an asteroid of this brightness. There's a second asteroid in the
image. Details are on the annotated image. Interestingly enough the
red POSS 2 plate picked up an asteroid on almost the same path but it
had just cleared the galaxy.

In preparing the annotated image I ran into a lot of very faint, distant
galaxies nearly all of which were listed at NED as being ELG which
stands for emission line galaxy. I've not seen that before. It's
apparently a new addition to their database in some areas of the sky.
One near the top of the image right of center is listed with a redshift
in excess of 1 which puts it nearly 8 billion light-years distant. For
me to pick one up at that distance I have to wonder if it doesn't have
an active core that rivals a quasar in brightness. That one is more
distant than one listed as a Quasar/AGN on the very left edge of the
image. Three of these ELGs are hiding by stars. I drew a line to them
to show it wasn't the star that was the ELG. In one case I also had to
mark the star they were so closely paired and matched in brightness.

There are several quasar candidates in the image (UvES) as well. Another
is a candidate BLAGN which stands for Broad Line Active Galactic
Nucleus. As is often the case there was a rather obvious galaxy a bit
northwest of NGC 3423 that isn't listed at NED at all. There may be
more, it was just the only one I happened across by accident.

For 2013 this one was taken on a "good" night for a change.

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:	NGC3423L4X10RGB2X10ID.JPG
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  #2  
Old October 27th 13, 09:49 PM posted to alt.binaries.pictures.astro
Stefan Lilge
external usenet poster
 
Posts: 2,269
Default ASTRO: NGC 3423

Wow, that's beautiful.
Went straight on my list, but at +5 degrees I can't get a lot of exposure
time, everything under +10 degrees only gets above my local horizon after
meridian.
While I usually would welcome an asteroid in an image I would have preferred
it to miss the galaxy by some arcseconds in this case...

Stefan

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

NGC 3423 is a nice, but rarely imaged, face on, multi-armed, blue spiral
in Sextans. NED classes it as SA(s)cd while the NGC project says Sc. It
is full of star clouds and HII regions. Redshift puts it about 63
million light-years away while Tully Fisher measurements say it is only
35 million light-years away. I found a crude image made from the few
HST frames available for it at
http://upload.wikimedia.org/wikipedi...-R606GB450.jpg
which seems to have resolution about what I'd expect for the further
distance but as my image starts to bring out the HII regions even
without H alpha data I have to suspect it is closer than the redshift
indicates. In any case it is a relatively nearby galaxy.

An asteroid happened to be tracking across its face when I took these
frames. Thanks to the bright background of the galaxy the color frames
show clearly when normally they'd be lost against the blackness of space
for an asteroid of this brightness. There's a second asteroid in the
image. Details are on the annotated image. Interestingly enough the
red POSS 2 plate picked up an asteroid on almost the same path but it
had just cleared the galaxy.

In preparing the annotated image I ran into a lot of very faint, distant
galaxies nearly all of which were listed at NED as being ELG which
stands for emission line galaxy. I've not seen that before. It's
apparently a new addition to their database in some areas of the sky.
One near the top of the image right of center is listed with a redshift
in excess of 1 which puts it nearly 8 billion light-years distant. For
me to pick one up at that distance I have to wonder if it doesn't have
an active core that rivals a quasar in brightness. That one is more
distant than one listed as a Quasar/AGN on the very left edge of the
image. Three of these ELGs are hiding by stars. I drew a line to them
to show it wasn't the star that was the ELG. In one case I also had to
mark the star they were so closely paired and matched in brightness.

There are several quasar candidates in the image (UvES) as well. Another
is a candidate BLAGN which stands for Broad Line Active Galactic
Nucleus. As is often the case there was a rather obvious galaxy a bit
northwest of NGC 3423 that isn't listed at NED at all. There may be
more, it was just the only one I happened across by accident.

For 2013 this one was taken on a "good" night for a change.

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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