ASTRO: Arp 50

Arp 50/NGC 1520 is located in eastern Cetus just across the border with
Aquarius and is just under 400 million light-years away. It is a rather
questionable object in many ways. First, many catalogs, including the
data base in The Sky 6 that I use to point my scope say it is NGC 5625
pointing me to the opposite side of the sky. Thus, when I set up the
script file for it then went to bed I got up to find blank images and an
error message telling me the object was beyond my scope's horizon
limits. By default the scope parked itself and shut down. So the
camera took great images of the observatory wall two feet away from the
front of the scope!

Arp 50 is really NGC 1520 so when I entered that I got a good image.
Not easy as it is about at my -15 degree declination limit.

Another reason this is a questionable object is Arp's classification of
it under spiral galaxies with small high surface brightness companions
on the arms. To what is he referring? He doesn't say. The galaxy has
several bright knots and arcs in the arms as well as a faint diffuse
blob on the end of the southern arm. This NED classifies as a second
galaxy. It certainly doesn't have a high surface brightness however
being nearly indistinguishable from the arm in Arp's image. There's a
nice bright knot in the other arm above a short bright arc. Is this
knot what Arp refers to, it does have a rather high surface brightness.
Some articles I found say there is no nearby galaxy at all. Others
call it a M51 type system. I can't find any high resolution images of
it on the net. In my image, a few seconds of arc above the "second
galaxy" according to NED and left is a near starlike object. The PSF
though is not right for a star. This could be due to it being in the
fuzz of the arm or because it is a distant galaxy. Flip a coin. I need
far more resolution to settle this.

I'm not the only one puzzled by this one. Science writer Courtney
Seligman is too. http://cseligman.com/text/atlas/ic15.htm Scroll down
for his take on this one as well as his image. Unfortunately, his image
isn't any better than Arp's. Arp's image was taken under what he calls
a seeing class of 1. He defines 3 as being 1" to 1.5" with each class
about twice as good (5 maximum) or bad (1 minimum). So Arp's image
would be taken under 4" or so seeing. And I thought my seeing was bad!
The POSS survey plate images are better than his of this entry.

If that low surface brightness blob is a separate galaxy is it nearby
and could it have the mass to pull out that arm? There's nothing on it
that I find to help answer this. To me this is a coin flip as to the
existence of a second galaxy. If none why is the arm distorted? It is
a rather lonely galaxy it would appear. NED has no distance data on any
other galaxy in the entire frame. One out of frame to the north is
listed at 1.5 billion light-years so not involved. 2MASX
J23581154-1400522, to the northeast is the only likely candidate I find
but without any distance data there's no way to know if this is a
reasonable one. Most galaxies in the field are cataloged only by the
APMUKS, an automatic plate measurement survey using the UK's Schmidt
telescope. This can't provide distance data. I marked one of these and
could have marked a hundred or so. As with many modern catalogs the
name gives its position, J2000 coordinates in this case.

My image did pick up 5 asteroids but again, another problem. One is
unknown to the Minor Planet Center and is apparently one they haven't
included as yet. It might even be undiscovered. If so it will remain
that way as this image was taken 2010 September 5.28UT so a bit late for
follow-up. 4 others were in their data base and are marked on the
annotated image. The unknown is marked with a question mark, the others
with their name and the planet center's magnitude estimate. One is
buried in the glow of a "bright" (7th magnitude so too faint to see
naked eye) F2V type star.

Arp's image:
http://ned.ipac.caltech.edu/level5/A...big_arp50.jpeg

14" LX200R @ f/10, L=4x10' RGB=2x10'x3, 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,

that's a neat little spiral.
I'd bet you could discover some new asteroids if you really wanted to...
But of course you could waste your time without finding any instead of
imaging those Arp galaxies ;-)

Stefan

"Rick Johnson" schrieb im Newsbeitrag
.com...
Arp 50/NGC 1520 is located in eastern Cetus just across the border with
Aquarius and is just under 400 million light-years away. It is a rather
questionable object in many ways. First, many catalogs, including the
data base in The Sky 6 that I use to point my scope say it is NGC 5625
pointing me to the opposite side of the sky. Thus, when I set up the
script file for it then went to bed I got up to find blank images and an
error message telling me the object was beyond my scope's horizon
limits. By default the scope parked itself and shut down. So the
camera took great images of the observatory wall two feet away from the
front of the scope!

Arp 50 is really NGC 1520 so when I entered that I got a good image.
Not easy as it is about at my -15 degree declination limit.

Another reason this is a questionable object is Arp's classification of
it under spiral galaxies with small high surface brightness companions
on the arms. To what is he referring? He doesn't say. The galaxy has
several bright knots and arcs in the arms as well as a faint diffuse
blob on the end of the southern arm. This NED classifies as a second
galaxy. It certainly doesn't have a high surface brightness however
being nearly indistinguishable from the arm in Arp's image. There's a
nice bright knot in the other arm above a short bright arc. Is this
knot what Arp refers to, it does have a rather high surface brightness.
Some articles I found say there is no nearby galaxy at all. Others
call it a M51 type system. I can't find any high resolution images of
it on the net. In my image, a few seconds of arc above the "second
galaxy" according to NED and left is a near starlike object. The PSF
though is not right for a star. This could be due to it being in the
fuzz of the arm or because it is a distant galaxy. Flip a coin. I need
far more resolution to settle this.

I'm not the only one puzzled by this one. Science writer Courtney
Seligman is too. http://cseligman.com/text/atlas/ic15.htm Scroll down
for his take on this one as well as his image. Unfortunately, his image
isn't any better than Arp's. Arp's image was taken under what he calls
a seeing class of 1. He defines 3 as being 1" to 1.5" with each class
about twice as good (5 maximum) or bad (1 minimum). So Arp's image
would be taken under 4" or so seeing. And I thought my seeing was bad!
The POSS survey plate images are better than his of this entry.

If that low surface brightness blob is a separate galaxy is it nearby
and could it have the mass to pull out that arm? There's nothing on it
that I find to help answer this. To me this is a coin flip as to the
existence of a second galaxy. If none why is the arm distorted? It is
a rather lonely galaxy it would appear. NED has no distance data on any
other galaxy in the entire frame. One out of frame to the north is
listed at 1.5 billion light-years so not involved. 2MASX
J23581154-1400522, to the northeast is the only likely candidate I find
but without any distance data there's no way to know if this is a
reasonable one. Most galaxies in the field are cataloged only by the
APMUKS, an automatic plate measurement survey using the UK's Schmidt
telescope. This can't provide distance data. I marked one of these and
could have marked a hundred or so. As with many modern catalogs the
name gives its position, J2000 coordinates in this case.

My image did pick up 5 asteroids but again, another problem. One is
unknown to the Minor Planet Center and is apparently one they haven't
included as yet. It might even be undiscovered. If so it will remain
that way as this image was taken 2010 September 5.28UT so a bit late for
follow-up. 4 others were in their data base and are marked on the
annotated image. The unknown is marked with a question mark, the others
with their name and the planet center's magnitude estimate. One is
buried in the glow of a "bright" (7th magnitude so too faint to see
naked eye) F2V type star.

Arp's image:
http://ned.ipac.caltech.edu/level5/A...big_arp50.jpeg

14" LX200R @ f/10, L=4x10' RGB=2x10'x3, 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".

I've lost count of how many unknowns I've found. Think it about 14 or
15. Looking at images a year later makes follow up impossible. Only
once did I notice an unknown the next day. I imaged where I calculated
it would be the following night but it was barely visible the first
night. Second night was worse and I couldn't find it. Third day was
cloudy. By then I gave up recovering it. Minor planet center wants two
days for discovery images. I should try to look at images the next day
but never seems to happen. With all the automated surveys I'd think a
guy like me has no chance but new ones keep turning up. So far my only
"discovery" was the asteroid that Arp saw as a jet in Arp 192. Jeff
Kanipe did the legwork needed for that. I only suggested this as a
possibility. I really favored a plate defect but that was wrong.

Rick

On 10/27/2011 4:26 PM, Stefan Lilge wrote:
Rick,

that's a neat little spiral.
I'd bet you could discover some new asteroids if you really wanted to...
But of course you could waste your time without finding any instead of
imaging those Arp galaxies ;-)

Stefan

"Rick schrieb im Newsbeitrag
.com...
Arp 50/NGC 1520 is located in eastern Cetus just across the border with
Aquarius and is just under 400 million light-years away. It is a rather
questionable object in many ways. First, many catalogs, including the
data base in The Sky 6 that I use to point my scope say it is NGC 5625
pointing me to the opposite side of the sky. Thus, when I set up the
script file for it then went to bed I got up to find blank images and an
error message telling me the object was beyond my scope's horizon
limits. By default the scope parked itself and shut down. So the
camera took great images of the observatory wall two feet away from the
front of the scope!

Arp 50 is really NGC 1520 so when I entered that I got a good image.
Not easy as it is about at my -15 degree declination limit.

Another reason this is a questionable object is Arp's classification of
it under spiral galaxies with small high surface brightness companions
on the arms. To what is he referring? He doesn't say. The galaxy has
several bright knots and arcs in the arms as well as a faint diffuse
blob on the end of the southern arm. This NED classifies as a second
galaxy. It certainly doesn't have a high surface brightness however
being nearly indistinguishable from the arm in Arp's image. There's a
nice bright knot in the other arm above a short bright arc. Is this
knot what Arp refers to, it does have a rather high surface brightness.
Some articles I found say there is no nearby galaxy at all. Others
call it a M51 type system. I can't find any high resolution images of
it on the net. In my image, a few seconds of arc above the "second
galaxy" according to NED and left is a near starlike object. The PSF
though is not right for a star. This could be due to it being in the
fuzz of the arm or because it is a distant galaxy. Flip a coin. I need
far more resolution to settle this.

I'm not the only one puzzled by this one. Science writer Courtney
Seligman is too. http://cseligman.com/text/atlas/ic15.htm Scroll down
for his take on this one as well as his image. Unfortunately, his image
isn't any better than Arp's. Arp's image was taken under what he calls
a seeing class of 1. He defines 3 as being 1" to 1.5" with each class
about twice as good (5 maximum) or bad (1 minimum). So Arp's image
would be taken under 4" or so seeing. And I thought my seeing was bad!
The POSS survey plate images are better than his of this entry.

If that low surface brightness blob is a separate galaxy is it nearby
and could it have the mass to pull out that arm? There's nothing on it
that I find to help answer this. To me this is a coin flip as to the
existence of a second galaxy. If none why is the arm distorted? It is
a rather lonely galaxy it would appear. NED has no distance data on any
other galaxy in the entire frame. One out of frame to the north is
listed at 1.5 billion light-years so not involved. 2MASX
J23581154-1400522, to the northeast is the only likely candidate I find
but without any distance data there's no way to know if this is a
reasonable one. Most galaxies in the field are cataloged only by the
APMUKS, an automatic plate measurement survey using the UK's Schmidt
telescope. This can't provide distance data. I marked one of these and
could have marked a hundred or so. As with many modern catalogs the
name gives its position, J2000 coordinates in this case.

My image did pick up 5 asteroids but again, another problem. One is
unknown to the Minor Planet Center and is apparently one they haven't
included as yet. It might even be undiscovered. If so it will remain
that way as this image was taken 2010 September 5.28UT so a bit late for
follow-up. 4 others were in their data base and are marked on the
annotated image. The unknown is marked with a question mark, the others
with their name and the planet center's magnitude estimate. One is
buried in the glow of a "bright" (7th magnitude so too faint to see
naked eye) F2V type star.

Arp's image:
http://ned.ipac.caltech.edu/level5/A...big_arp50.jpeg

14" LX200R @ f/10, L=4x10' RGB=2x10'x3, 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".