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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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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
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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
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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
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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
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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
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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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