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#1
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ASTRO: NGC 7094 and a bonus nebula
Despite my return to galaxies last post I'm not done with planetary
nebula. NGC 7094 a planetary in Pegasus not far from the famous globular cluster M15. The central star in this nebula is a rather odd star. It is known as a hybrid PG 1159 star. What this means is that it, first off, has an unusual amount of hydrogen left in its atmosphere. Secondly it is a variable star. White dwarf stars are normally dead stars only giving off heat and light stored in them when their nuclear furnaces were still working. When they die they throw off the outer atmosphere that still has hydrogen, creating the planetary nebula, and retaining the core of heavier elements created by the nuclear furnace. They get a small amount of energy from gravitational collapse as they cool but they shouldn't very in brightness. But some do. It is thought that the outer atmosphere of the star becomes more or less opaque depending on the ionization level of certain heavy elements such as iron in the atmosphere. It is this variation of ionization that makes the star appear to vary in brightness. In fact it doesn't, its just that the atmosphere blocks the light at time. Such cycles are very irregular. In this case the star varies at a rate of 2000 to 5000 seconds. Since my exposure of this guy was 6000 seconds it may have varied 3 times during my exposure! Thus catching this isn't easy, nor would I try. I knew this before I took the image. What I didn't know was that it shares the field with a very faint nebulosity. This nebulosity isn't listed in any catalog I have, nor does it appear to be galactic cirrus. Not expecting it I severely underexposed for it, especially the color frames which are very noisy. Don't consider the color of this faint nebulosity as at all correct, the color is mostly noise. If anyone knows what it is please let me know. I need to go back and try a much longer exposure. But something is reflecting into my field. When I centered the nebula a rather bright ghostly nebula appeared to the west of the nebula. I have no idea where the reflection came from, M15? To get rid of it I had to lower the object. Raising it didn't help. Since the nebula is mostly "below" the planetary that means I lost some of it, though I didn't realize it at the time. I can't find any reliable distance data for this planetary. Again, if anyone knows let me know. Conditions went from fair to bad during this exposure. The loss of resolution caused the blue and especially green frames to be "defocused" creating the odd blue-green halos around bright stars as well as making them larger than usual. Yet another reason to redo this one but I have such a backlog of objects not taken the first time it is hard to go back and reimage those I should. 14" LX200R @ f/10, L=4x10', RGB 2x10' 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". |
#2
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ASTRO: NGC 7094 and a bonus nebula
Neat image Rick, very good detail. Another one to reshoot, to my surprise I
found that I have not imaged this nebula in the last few years. Stefan "Rick Johnson" schrieb im Newsbeitrag ster.com... Despite my return to galaxies last post I'm not done with planetary nebula. NGC 7094 a planetary in Pegasus not far from the famous globular cluster M15. The central star in this nebula is a rather odd star. It is known as a hybrid PG 1159 star. What this means is that it, first off, has an unusual amount of hydrogen left in its atmosphere. Secondly it is a variable star. White dwarf stars are normally dead stars only giving off heat and light stored in them when their nuclear furnaces were still working. When they die they throw off the outer atmosphere that still has hydrogen, creating the planetary nebula, and retaining the core of heavier elements created by the nuclear furnace. They get a small amount of energy from gravitational collapse as they cool but they shouldn't very in brightness. But some do. It is thought that the outer atmosphere of the star becomes more or less opaque depending on the ionization level of certain heavy elements such as iron in the atmosphere. It is this variation of ionization that makes the star appear to vary in brightness. In fact it doesn't, its just that the atmosphere blocks the light at time. Such cycles are very irregular. In this case the star varies at a rate of 2000 to 5000 seconds. Since my exposure of this guy was 6000 seconds it may have varied 3 times during my exposure! Thus catching this isn't easy, nor would I try. I knew this before I took the image. What I didn't know was that it shares the field with a very faint nebulosity. This nebulosity isn't listed in any catalog I have, nor does it appear to be galactic cirrus. Not expecting it I severely underexposed for it, especially the color frames which are very noisy. Don't consider the color of this faint nebulosity as at all correct, the color is mostly noise. If anyone knows what it is please let me know. I need to go back and try a much longer exposure. But something is reflecting into my field. When I centered the nebula a rather bright ghostly nebula appeared to the west of the nebula. I have no idea where the reflection came from, M15? To get rid of it I had to lower the object. Raising it didn't help. Since the nebula is mostly "below" the planetary that means I lost some of it, though I didn't realize it at the time. I can't find any reliable distance data for this planetary. Again, if anyone knows let me know. Conditions went from fair to bad during this exposure. The loss of resolution caused the blue and especially green frames to be "defocused" creating the odd blue-green halos around bright stars as well as making them larger than usual. Yet another reason to redo this one but I have such a backlog of objects not taken the first time it is hard to go back and reimage those I should. 14" LX200R @ f/10, L=4x10', RGB 2x10' 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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ASTRO: NGC 7094 and a bonus nebula
Nice image Rick! That planetary is very blue. That extra nebula is not
surprising though. I saw an image on Astromart yesterday posted by Roland Christen that showed intergalactic dust up to and around NGC 7331 and Stephen's Quintet. I have also seen images of similar nebula around M81-m82 taken by Tom Davis with a 10ASA. Joe "Rick Johnson" wrote in message ster.com... Despite my return to galaxies last post I'm not done with planetary nebula. NGC 7094 a planetary in Pegasus not far from the famous globular cluster M15. The central star in this nebula is a rather odd star. It is known as a hybrid PG 1159 star. What this means is that it, first off, has an unusual amount of hydrogen left in its atmosphere. Secondly it is a variable star. White dwarf stars are normally dead stars only giving off heat and light stored in them when their nuclear furnaces were still working. When they die they throw off the outer atmosphere that still has hydrogen, creating the planetary nebula, and retaining the core of heavier elements created by the nuclear furnace. They get a small amount of energy from gravitational collapse as they cool but they shouldn't very in brightness. But some do. It is thought that the outer atmosphere of the star becomes more or less opaque depending on the ionization level of certain heavy elements such as iron in the atmosphere. It is this variation of ionization that makes the star appear to vary in brightness. In fact it doesn't, its just that the atmosphere blocks the light at time. Such cycles are very irregular. In this case the star varies at a rate of 2000 to 5000 seconds. Since my exposure of this guy was 6000 seconds it may have varied 3 times during my exposure! Thus catching this isn't easy, nor would I try. I knew this before I took the image. What I didn't know was that it shares the field with a very faint nebulosity. This nebulosity isn't listed in any catalog I have, nor does it appear to be galactic cirrus. Not expecting it I severely underexposed for it, especially the color frames which are very noisy. Don't consider the color of this faint nebulosity as at all correct, the color is mostly noise. If anyone knows what it is please let me know. I need to go back and try a much longer exposure. But something is reflecting into my field. When I centered the nebula a rather bright ghostly nebula appeared to the west of the nebula. I have no idea where the reflection came from, M15? To get rid of it I had to lower the object. Raising it didn't help. Since the nebula is mostly "below" the planetary that means I lost some of it, though I didn't realize it at the time. I can't find any reliable distance data for this planetary. Again, if anyone knows let me know. Conditions went from fair to bad during this exposure. The loss of resolution caused the blue and especially green frames to be "defocused" creating the odd blue-green halos around bright stars as well as making them larger than usual. Yet another reason to redo this one but I have such a backlog of objects not taken the first time it is hard to go back and reimage those I should. 14" LX200R @ f/10, L=4x10', RGB 2x10' 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". ---------------------------------------------------------------------------- ---- |
#4
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ASTRO: NGC 7094 and a bonus nebula
Joe,
As I mentioned in the post, I don't think this is galactic cirrus as you mention in connection with these other objects. The nebula in my shot is strongest in red and virtually absent in blue. Cirrus would show nearly equally in all three from the images of it I've seen. Also I've taken these other objects at the same or longer exposure time and while I can find the cirrus in them it is too weak to bring out. This is several times stronger than any cirrus I know of. Nor does it have the wispy dusty look of cirrus. This looks more like ERE emission from the response in the RGB filters rather than reflective though some Halpha may be involved as well. A shot with the H alpha filter would answer the latter. Since it was so weak in blue H alpha can't be a major player or I'd see H beta in the blue. Though it was getting lower in the sky when I took the blue so it might be lost to blue extinction but I wasn't that low per the headers. But ERE is very smooth, not clumpy like this so I don't like that idea either. I was hoping someone might already know of it. I see no hint of it in my M15 shot but that is also a far shorter exposure using only 2 minute subs to prevent the core from saturating. Rick J McBride wrote: Nice image Rick! That planetary is very blue. That extra nebula is not surprising though. I saw an image on Astromart yesterday posted by Roland Christen that showed intergalactic dust up to and around NGC 7331 and Stephen's Quintet. I have also seen images of similar nebula around M81-m82 taken by Tom Davis with a 10ASA. Joe "Rick Johnson" wrote in message ster.com... Despite my return to galaxies last post I'm not done with planetary nebula. NGC 7094 a planetary in Pegasus not far from the famous globular cluster M15. The central star in this nebula is a rather odd star. It is known as a hybrid PG 1159 star. What this means is that it, first off, has an unusual amount of hydrogen left in its atmosphere. Secondly it is a variable star. White dwarf stars are normally dead stars only giving off heat and light stored in them when their nuclear furnaces were still working. When they die they throw off the outer atmosphere that still has hydrogen, creating the planetary nebula, and retaining the core of heavier elements created by the nuclear furnace. They get a small amount of energy from gravitational collapse as they cool but they shouldn't very in brightness. But some do. It is thought that the outer atmosphere of the star becomes more or less opaque depending on the ionization level of certain heavy elements such as iron in the atmosphere. It is this variation of ionization that makes the star appear to vary in brightness. In fact it doesn't, its just that the atmosphere blocks the light at time. Such cycles are very irregular. In this case the star varies at a rate of 2000 to 5000 seconds. Since my exposure of this guy was 6000 seconds it may have varied 3 times during my exposure! Thus catching this isn't easy, nor would I try. I knew this before I took the image. What I didn't know was that it shares the field with a very faint nebulosity. This nebulosity isn't listed in any catalog I have, nor does it appear to be galactic cirrus. Not expecting it I severely underexposed for it, especially the color frames which are very noisy. Don't consider the color of this faint nebulosity as at all correct, the color is mostly noise. If anyone knows what it is please let me know. I need to go back and try a much longer exposure. But something is reflecting into my field. When I centered the nebula a rather bright ghostly nebula appeared to the west of the nebula. I have no idea where the reflection came from, M15? To get rid of it I had to lower the object. Raising it didn't help. Since the nebula is mostly "below" the planetary that means I lost some of it, though I didn't realize it at the time. I can't find any reliable distance data for this planetary. Again, if anyone knows let me know. Conditions went from fair to bad during this exposure. The loss of resolution caused the blue and especially green frames to be "defocused" creating the odd blue-green halos around bright stars as well as making them larger than usual. Yet another reason to redo this one but I have such a backlog of objects not taken the first time it is hard to go back and reimage those I should. 14" LX200R @ f/10, L=4x10', RGB 2x10' 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". |
#5
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ASTRO: NGC 7094 and a bonus nebula
Hey Man, I'm not arguing what it is. I'm just saying that I'm not surprised
that you picked it up. That stuff is everywhere up there and I hope to have a imaging system strong enough to capture it some day. Joe "Rick Johnson" wrote in message ster.com... Joe, As I mentioned in the post, I don't think this is galactic cirrus as you mention in connection with these other objects. The nebula in my shot is strongest in red and virtually absent in blue. Cirrus would show nearly equally in all three from the images of it I've seen. Also I've taken these other objects at the same or longer exposure time and while I can find the cirrus in them it is too weak to bring out. This is several times stronger than any cirrus I know of. Nor does it have the wispy dusty look of cirrus. This looks more like ERE emission from the response in the RGB filters rather than reflective though some Halpha may be involved as well. A shot with the H alpha filter would answer the latter. Since it was so weak in blue H alpha can't be a major player or I'd see H beta in the blue. Though it was getting lower in the sky when I took the blue so it might be lost to blue extinction but I wasn't that low per the headers. But ERE is very smooth, not clumpy like this so I don't like that idea either. I was hoping someone might already know of it. I see no hint of it in my M15 shot but that is also a far shorter exposure using only 2 minute subs to prevent the core from saturating. Rick J McBride wrote: Nice image Rick! That planetary is very blue. That extra nebula is not surprising though. I saw an image on Astromart yesterday posted by Roland Christen that showed intergalactic dust up to and around NGC 7331 and Stephen's Quintet. I have also seen images of similar nebula around M81-m82 taken by Tom Davis with a 10ASA. Joe "Rick Johnson" wrote in message ster.com... Despite my return to galaxies last post I'm not done with planetary nebula. NGC 7094 a planetary in Pegasus not far from the famous globular cluster M15. The central star in this nebula is a rather odd star. It is known as a hybrid PG 1159 star. What this means is that it, first off, has an unusual amount of hydrogen left in its atmosphere. Secondly it is a variable star. White dwarf stars are normally dead stars only giving off heat and light stored in them when their nuclear furnaces were still working. When they die they throw off the outer atmosphere that still has hydrogen, creating the planetary nebula, and retaining the core of heavier elements created by the nuclear furnace. They get a small amount of energy from gravitational collapse as they cool but they shouldn't very in brightness. But some do. It is thought that the outer atmosphere of the star becomes more or less opaque depending on the ionization level of certain heavy elements such as iron in the atmosphere. It is this variation of ionization that makes the star appear to vary in brightness. In fact it doesn't, its just that the atmosphere blocks the light at time. Such cycles are very irregular. In this case the star varies at a rate of 2000 to 5000 seconds. Since my exposure of this guy was 6000 seconds it may have varied 3 times during my exposure! Thus catching this isn't easy, nor would I try. I knew this before I took the image. What I didn't know was that it shares the field with a very faint nebulosity. This nebulosity isn't listed in any catalog I have, nor does it appear to be galactic cirrus. Not expecting it I severely underexposed for it, especially the color frames which are very noisy. Don't consider the color of this faint nebulosity as at all correct, the color is mostly noise. If anyone knows what it is please let me know. I need to go back and try a much longer exposure. But something is reflecting into my field. When I centered the nebula a rather bright ghostly nebula appeared to the west of the nebula. I have no idea where the reflection came from, M15? To get rid of it I had to lower the object. Raising it didn't help. Since the nebula is mostly "below" the planetary that means I lost some of it, though I didn't realize it at the time. I can't find any reliable distance data for this planetary. Again, if anyone knows let me know. Conditions went from fair to bad during this exposure. The loss of resolution caused the blue and especially green frames to be "defocused" creating the odd blue-green halos around bright stars as well as making them larger than usual. Yet another reason to redo this one but I have such a backlog of objects not taken the first time it is hard to go back and reimage those I should. 14" LX200R @ f/10, L=4x10', RGB 2x10' 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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