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NGC 4236 Another low surface brightness M81 group galaxy



 
 
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  #1  
Old March 16th 08, 06:42 AM posted to alt.binaries.pictures.astro
Rick Johnson[_3_]
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Posts: 262
Default NGC 4236 Another low surface brightness M81 group galaxy

It seems the only clear nights I get are also moon lit. I'm not all
that great at processing moon lit images. Still it sort of works.

This galaxy was much bigger than I expected. It is listed as about 6
minutes shorter than M81 which fit nicely on my frame but this guy is
actually larger but tilted about the same. Looking at the short 5"
image I used for checking if the mount hit it I saw a star that was dead
center on my chip and seemed dead center along the bright bar of the
galaxy. Not until I processed it and could see the fainter parts did I
realize the southern part extends farther. The star was indeed about
the center of the bar but this galaxy is quite unsymmetrical. Not sure
if I missed anything below the southern end or not.

This is one blue galaxy. At first I thought it due to moonlight but
checking the few other color images it seems right. How a galaxy has
mostly brilliant blue stars can be so faint I'm not sure. Some reports
call it heavily obscured but I'd expect that to redden it some. I see
no sign of that.

I am impressed by the number of faint galaxies in this image. Looks to
me that there may be more of them than foreground stars. Unfortunately,
seeing wasn't all that good so its hard to tell.

This was taken over two nights. I took my usual 4x10' and 2x10 minute
series but it was so low luminosity I waited for another clear night to
do it again. First night had a 3 day old moon that set before I took
color data. I used those frames to check that my color was correct.
Then the last frame was taken at 5 days when the moon was in the sky
giving me fits on all frames. Still, I got a better result using all
frames. Seeing was better the moon lit night as well which helped a bit
as well as fogging the faint stuff.

In all this is one surprisingly big galaxy. It is listed at 11.5
million light years (M81 is 12). Brightest blue stars are listed at
19th magnitude and as this shot easily goes well below that some of
those "stars" in the galaxy really are stars and not clusters it would
seem. Which is which is the question.

H-alpha might show up some HII regions but I sure don't see any in the
RGB data. They must be smaller than my seeing allowed me to resolve.

Earlier this galaxy was so high a declination it was in my Polaris tree
all the time. Last year I had no trouble reaching 70 degrees but
couldn't this winter. 67 was about the limit unless I wanted to image
many nights using a 25 minute window, then I could hit 68. But now I'm
back to 70. Snow is out of the tree after high winds blew it all far to
the north of me. That means the tree leans toward me when snow covered.
I waded through the snow (still 18" on the ground) to get a good look
at it with a plumb bob. It is leaning about 5 degrees toward the
observatory even now, and has been apparently, but with a heavy snow
load it leans even more. Not sure if that means I could have a bisected
observatory or not. I think I'll have a tree guy I know give his
assessment. It saves me a lot of time raking snow off the roof.
Nothing like standing atop a 10' ladder atop a 9' deck using a 26' snow
rake trying to remove snow off the observatory. It's a long way down
from up there! Thanks to the tree I didn't need to do it at all last
year (light snow) and only once this year (normal snow). But the snow
on the house roof that isn't protected indicates I'd have been doing it
about 8 times this winter without the tree. When the snow load is heavy
rolling the roof would dump it all into the observatory as it rolled
back. That I don't need. I only clean off the south side as the north
side dumps only outside the observatory and isn't a problem. So I'm now
in a quandary over the tree. Unlike my Meridian Tree, this one is legal
to cut, though at 100 feet expensive to do as it has to be tied off and
cut in short sections to be sure it doesn't fall on the observatory.

14" LX200R @ f/10, L=8x10' binned 2x2, RGB=4x10' 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".

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  #2  
Old March 16th 08, 10:27 AM posted to alt.binaries.pictures.astro
DvandenH
external usenet poster
 
Posts: 143
Default NGC 4236 Another low surface brightness M81 group galaxy

That's exactly what i am experiencing here too Rick, clear night ....moon
shines.
Very frustrating..
But you managed to get a beautifull shot at this one. nice processing too.

reg
Dirk


"Rick Johnson" wrote in message
...
It seems the only clear nights I get are also moon lit. I'm not all
that great at processing moon lit images. Still it sort of works.

This galaxy was much bigger than I expected. It is listed as about 6
minutes shorter than M81 which fit nicely on my frame but this guy is
actually larger but tilted about the same. Looking at the short 5"
image I used for checking if the mount hit it I saw a star that was dead
center on my chip and seemed dead center along the bright bar of the
galaxy. Not until I processed it and could see the fainter parts did I
realize the southern part extends farther. The star was indeed about
the center of the bar but this galaxy is quite unsymmetrical. Not sure
if I missed anything below the southern end or not.

This is one blue galaxy. At first I thought it due to moonlight but
checking the few other color images it seems right. How a galaxy has
mostly brilliant blue stars can be so faint I'm not sure. Some reports
call it heavily obscured but I'd expect that to redden it some. I see
no sign of that.

I am impressed by the number of faint galaxies in this image. Looks to
me that there may be more of them than foreground stars. Unfortunately,
seeing wasn't all that good so its hard to tell.

This was taken over two nights. I took my usual 4x10' and 2x10 minute
series but it was so low luminosity I waited for another clear night to
do it again. First night had a 3 day old moon that set before I took
color data. I used those frames to check that my color was correct.
Then the last frame was taken at 5 days when the moon was in the sky
giving me fits on all frames. Still, I got a better result using all
frames. Seeing was better the moon lit night as well which helped a bit
as well as fogging the faint stuff.

In all this is one surprisingly big galaxy. It is listed at 11.5
million light years (M81 is 12). Brightest blue stars are listed at
19th magnitude and as this shot easily goes well below that some of
those "stars" in the galaxy really are stars and not clusters it would
seem. Which is which is the question.

H-alpha might show up some HII regions but I sure don't see any in the
RGB data. They must be smaller than my seeing allowed me to resolve.

Earlier this galaxy was so high a declination it was in my Polaris tree
all the time. Last year I had no trouble reaching 70 degrees but
couldn't this winter. 67 was about the limit unless I wanted to image
many nights using a 25 minute window, then I could hit 68. But now I'm
back to 70. Snow is out of the tree after high winds blew it all far to
the north of me. That means the tree leans toward me when snow covered.
I waded through the snow (still 18" on the ground) to get a good look
at it with a plumb bob. It is leaning about 5 degrees toward the
observatory even now, and has been apparently, but with a heavy snow
load it leans even more. Not sure if that means I could have a bisected
observatory or not. I think I'll have a tree guy I know give his
assessment. It saves me a lot of time raking snow off the roof.
Nothing like standing atop a 10' ladder atop a 9' deck using a 26' snow
rake trying to remove snow off the observatory. It's a long way down
from up there! Thanks to the tree I didn't need to do it at all last
year (light snow) and only once this year (normal snow). But the snow
on the house roof that isn't protected indicates I'd have been doing it
about 8 times this winter without the tree. When the snow load is heavy
rolling the roof would dump it all into the observatory as it rolled
back. That I don't need. I only clean off the south side as the north
side dumps only outside the observatory and isn't a problem. So I'm now
in a quandary over the tree. Unlike my Meridian Tree, this one is legal
to cut, though at 100 feet expensive to do as it has to be tied off and
cut in short sections to be sure it doesn't fall on the observatory.

14" LX200R @ f/10, L=8x10' binned 2x2, RGB=4x10' 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".


  #3  
Old March 16th 08, 08:43 PM posted to alt.binaries.pictures.astro
John N. Gretchen III
external usenet poster
 
Posts: 460
Default NGC 4236 Another low surface brightness M81 group galaxy

Nice shot Rick! You have a ton more signal than I got with my image
earlier this year...

Rick Johnson wrote:
It seems the only clear nights I get are also moon lit. I'm not all
that great at processing moon lit images. Still it sort of works.

This galaxy was much bigger than I expected. It is listed as about 6
minutes shorter than M81 which fit nicely on my frame but this guy is
actually larger but tilted about the same. Looking at the short 5"
image I used for checking if the mount hit it I saw a star that was dead
center on my chip and seemed dead center along the bright bar of the
galaxy. Not until I processed it and could see the fainter parts did I
realize the southern part extends farther. The star was indeed about
the center of the bar but this galaxy is quite unsymmetrical. Not sure
if I missed anything below the southern end or not.

This is one blue galaxy. At first I thought it due to moonlight but
checking the few other color images it seems right. How a galaxy has
mostly brilliant blue stars can be so faint I'm not sure. Some reports
call it heavily obscured but I'd expect that to redden it some. I see
no sign of that.

I am impressed by the number of faint galaxies in this image. Looks to
me that there may be more of them than foreground stars. Unfortunately,
seeing wasn't all that good so its hard to tell.

This was taken over two nights. I took my usual 4x10' and 2x10 minute
series but it was so low luminosity I waited for another clear night to
do it again. First night had a 3 day old moon that set before I took
color data. I used those frames to check that my color was correct.
Then the last frame was taken at 5 days when the moon was in the sky
giving me fits on all frames. Still, I got a better result using all
frames. Seeing was better the moon lit night as well which helped a bit
as well as fogging the faint stuff.

In all this is one surprisingly big galaxy. It is listed at 11.5
million light years (M81 is 12). Brightest blue stars are listed at
19th magnitude and as this shot easily goes well below that some of
those "stars" in the galaxy really are stars and not clusters it would
seem. Which is which is the question.

H-alpha might show up some HII regions but I sure don't see any in the
RGB data. They must be smaller than my seeing allowed me to resolve.

Earlier this galaxy was so high a declination it was in my Polaris tree
all the time. Last year I had no trouble reaching 70 degrees but
couldn't this winter. 67 was about the limit unless I wanted to image
many nights using a 25 minute window, then I could hit 68. But now I'm
back to 70. Snow is out of the tree after high winds blew it all far to
the north of me. That means the tree leans toward me when snow covered.
I waded through the snow (still 18" on the ground) to get a good look
at it with a plumb bob. It is leaning about 5 degrees toward the
observatory even now, and has been apparently, but with a heavy snow
load it leans even more. Not sure if that means I could have a bisected
observatory or not. I think I'll have a tree guy I know give his
assessment. It saves me a lot of time raking snow off the roof. Nothing
like standing atop a 10' ladder atop a 9' deck using a 26' snow rake
trying to remove snow off the observatory. It's a long way down from up
there! Thanks to the tree I didn't need to do it at all last year
(light snow) and only once this year (normal snow). But the snow on the
house roof that isn't protected indicates I'd have been doing it about 8
times this winter without the tree. When the snow load is heavy rolling
the roof would dump it all into the observatory as it rolled back. That
I don't need. I only clean off the south side as the north side dumps
only outside the observatory and isn't a problem. So I'm now in a
quandary over the tree. Unlike my Meridian Tree, this one is legal to
cut, though at 100 feet expensive to do as it has to be tied off and cut
in short sections to be sure it doesn't fall on the observatory.

14" LX200R @ f/10, L=8x10' binned 2x2, RGB=4x10' binned 3x3,
STL-11000XM, Paramount ME

Rick

------------------------------------------------------------------------


--
John N. Gretchen III
N5JNG NCS304
http://www.tisd.net/~jng3
  #4  
Old March 16th 08, 09:34 PM posted to alt.binaries.pictures.astro
Rick Johnson[_3_]
external usenet poster
 
Posts: 262
Default NGC 4236 Another low surface brightness M81 group galaxy

I'd forgotten your post. Back then I had snow in the Polaris Tree and
couldn't reach it. But high winds a couple weeks ago blew it all out
and now it doesn't lean so far toward the observatory so I was able to
reach it at a point when it was about as far south east as it gets. Had
less than two hours a night however.

I'm puzzled by your apparent lack of signal. My 6" f/4 was only about
an f stop faster than your f/6 yet had 10 times the signal you seem to
get in the same time. Makes me wonder if there's some issue with the
camera or how the images are processed. Think your old 6" f/6 used to
give far more signal as well in the final result.

Your just posted M97 was 1:30. Most sources say one shot color gets the
job done in less time than LRGB.
http://www.astromart.com/articles/ar...article_id=639

Yet my shot in 1:25 goes far deeper.
http://www.spacebanter.com/attachmen...ntid=519&stc=1

I'm not sure what's going on here.

Rick


John N. Gretchen III wrote:

Nice shot Rick! You have a ton more signal than I got with my image
earlier this year...


  #5  
Old March 16th 08, 10:01 PM posted to alt.binaries.pictures.astro
John N. Gretchen III
external usenet poster
 
Posts: 460
Default NGC 4236 Another low surface brightness M81 group galaxy

The moon washed this data out pretty good, also I was using windows rgb
proof setup in Photoshop which is pretty dark when viewed on my monitor.
I am going to replace the rgb chip with a mono ccd, order form on my
desk needing to be faxed to Kodak. I don't know if there is a problem
with the camera, I've send images ti Sbig and they say everything is OK.
I want to go mono for photometric work anyway. We will see.

Rick Johnson wrote:
I'd forgotten your post. Back then I had snow in the Polaris Tree and
couldn't reach it. But high winds a couple weeks ago blew it all out
and now it doesn't lean so far toward the observatory so I was able to
reach it at a point when it was about as far south east as it gets. Had
less than two hours a night however.

I'm puzzled by your apparent lack of signal. My 6" f/4 was only about
an f stop faster than your f/6 yet had 10 times the signal you seem to
get in the same time. Makes me wonder if there's some issue with the
camera or how the images are processed. Think your old 6" f/6 used to
give far more signal as well in the final result.

Your just posted M97 was 1:30. Most sources say one shot color gets the
job done in less time than LRGB.
http://www.astromart.com/articles/ar...article_id=639

Yet my shot in 1:25 goes far deeper.
http://www.spacebanter.com/attachmen...ntid=519&stc=1

I'm not sure what's going on here.

Rick


John N. Gretchen III wrote:

Nice shot Rick! You have a ton more signal than I got with my image
earlier this year...



--
John N. Gretchen III
N5JNG NCS304
http://www.tisd.net/~jng3
  #6  
Old March 18th 08, 04:28 PM posted to alt.binaries.pictures.astro
George Normandin[_1_]
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Posts: 1,022
Default NGC 4236 Another low surface brightness M81 group galaxy


"Rick Johnson" wrote
....
It seems the only clear nights I get are also moon lit


Rick,

That's better than here, where we have had no clear nights at all for
several weeks. There have been several clear days, but I didn't get the
solar h-alpha out.


This galaxy was much bigger than I expected......


If you ever re-do it you can just rotate the camera.

Like all of the smaller galaxies in the M-81 group, this one has probably
been involved in collisions with M-81 and that sparked massive star
formation. The entire group is immersed in dust and gas. Also, as some
amateur astronomers doing deep wide-fields have "discovered" (or at least
brought to everyone's attention) the area of Ursa Major is filled with high
galactic altitude Milky Way dust. Still, I think NGC 4236 is just a very
blue galaxy.

I also found the background galaxies interesting. There seems to be a
distant cluster behind the top portion of NGC 4236 (as shown in your
picture).

Perhaps you could just cut of the top 5 or 10 feet of the offending tree?
If the state gives you a hard time, blame it on the squirrels.

George N



  #7  
Old March 18th 08, 06:19 PM posted to alt.binaries.pictures.astro
Rick Johnson[_3_]
external usenet poster
 
Posts: 262
Default NGC 4236 Another low surface brightness M81 group galaxy



George Normandin wrote:

"Rick Johnson" wrote
...

It seems the only clear nights I get are also moon lit



Rick,

That's better than here, where we have had no clear nights at all for
several weeks. There have been several clear days, but I didn't get the
solar h-alpha out.



This galaxy was much bigger than I expected......



If you ever re-do it you can just rotate the camera.

Like all of the smaller galaxies in the M-81 group, this one has probably
been involved in collisions with M-81 and that sparked massive star
formation. The entire group is immersed in dust and gas. Also, as some
amateur astronomers doing deep wide-fields have "discovered" (or at least
brought to everyone's attention) the area of Ursa Major is filled with high
galactic altitude Milky Way dust. Still, I think NGC 4236 is just a very
blue galaxy.

I also found the background galaxies interesting. There seems to be a
distant cluster behind the top portion of NGC 4236 (as shown in your
picture).

Perhaps you could just cut of the top 5 or 10 feet of the offending tree?
If the state gives you a hard time, blame it on the squirrels.

George N


There's no restrictions on what I do with the that tree. But the part
of it that protects against snow and saves me a heck of a lot of snow
raking is also the part that would have to go to help the view. When I
asked the tree guy about it when I cut other trees to open my sky he
said cutting it back like that would likely kill it as that was the part
getting the most sun and was supplying most of the trees needs.

But now that I see it is leaning toward the observatory when loaded with
snow I will be calling again but right now you can't get near it with a
bucket truck. Also now that the other trees are gone it is going to
grow this way as that's where the light is.

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".

 




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