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ASTRO: Nova Delphini 2013 revisited 25 days later
I originally imaged Nova Delphini 2013 on August 29. I've tried several
time since to reimage it to see if it changed but the weather has made a mess of all attempts. Now with it being over a month later and the moon in the area, I went through all the attempts and found one that was sort of usable. Seeing was poor by comparison so stars are much larger. This makes them appear brighter but I've actually processed them virtually the same. The difference is just due to seeing and changes in transparency. The second attempt was taken September 23 so 6 days shy of a month later. Two differences are obvious. First it has changed color. This was rather expected. Many nova (but not the previous nova in Delphinus in 1967) blow out huge shells of hydrogen gas that glows in typical hydrogen alpha red and weaker hydrogen beta blue-green. Since the red dominates the star appears to turn red though it is actually the as yet unresolved hydrogen shell it expelled that gives it the red color. The star is still blue hot from the eruption. The other change, also as expected (but again not the case with the 1967 nova in Delphinus) is that it has gotten fainter. I've included a side by side comparison as well as the full frame from September. Both the August and September images were taken precisely the same way in order to try and preserve comparability. I should add that while the nova appears to have a red halo about it that is just glare from the star being so bright. This is the same as the blue glare around the earlier image but colored by the H alpha shell. The actual hydrogen shell is still an unresolved point source same as the star itself. 14" LX200R @ f/10, RGB=1x10' each, STL-11000XM, Paramount ME Rick -- Prefix is correct. Domain is arvig dot net |
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ASTRO: Nova Delphini 2013 revisited 25 days later
Rick,
the change in colour is quite astounding... Stefan "Rick Johnson" schrieb im Newsbeitrag . com... I originally imaged Nova Delphini 2013 on August 29. I've tried several time since to reimage it to see if it changed but the weather has made a mess of all attempts. Now with it being over a month later and the moon in the area, I went through all the attempts and found one that was sort of usable. Seeing was poor by comparison so stars are much larger. This makes them appear brighter but I've actually processed them virtually the same. The difference is just due to seeing and changes in transparency. The second attempt was taken September 23 so 6 days shy of a month later. Two differences are obvious. First it has changed color. This was rather expected. Many nova (but not the previous nova in Delphinus in 1967) blow out huge shells of hydrogen gas that glows in typical hydrogen alpha red and weaker hydrogen beta blue-green. Since the red dominates the star appears to turn red though it is actually the as yet unresolved hydrogen shell it expelled that gives it the red color. The star is still blue hot from the eruption. The other change, also as expected (but again not the case with the 1967 nova in Delphinus) is that it has gotten fainter. I've included a side by side comparison as well as the full frame from September. Both the August and September images were taken precisely the same way in order to try and preserve comparability. I should add that while the nova appears to have a red halo about it that is just glare from the star being so bright. This is the same as the blue glare around the earlier image but colored by the H alpha shell. The actual hydrogen shell is still an unresolved point source same as the star itself. 14" LX200R @ f/10, RGB=1x10' each, STL-11000XM, Paramount ME Rick -- Prefix is correct. Domain is arvig dot net |
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ASTRO: Nova Delphini 2013 revisited 25 days later
I've seen this quite often with Nova. For a while they get redder as
the star still has sufficient UV light and shell's density reaches optimum values. Then the red and the star fade back to obscurity. I may have caught it when color was near max. It was fainter in earlier images and cloudy since so haven't seen what it has done since the 23rd. GK Persei was an exception since the star has stayed bright in UV (and visible light) it continues to light up its ejecta over 100 years later. That is an exception however. Nova Cygni 1975 was pretty well faded to nothing in just a month's time yet hit magnitude 2 at maximum. It was about magnitude 6 or fainter when the shell was most obvious only a week or so later. It will be interesting to see how long this one hangs in there. The 1967 Delphini nova showed no hydrogen and was brighter months after it blew rather than dimmer. I stayed as bright or brighter than its first peak for many months. It is still there at mag 13 or so though it was much fainter prior to the eruption. Like GK Persei it is a variable star since the nova. Maybe in 100 years it too will have a "fireworks burst" nebula around it. Maybe I should image it to see get a base image in case something shows up. Rick On 10/14/2013 4:53 PM, Stefan Lilge wrote: Rick, the change in colour is quite astounding... Stefan "Rick Johnson" schrieb im Newsbeitrag . com... I originally imaged Nova Delphini 2013 on August 29. I've tried several time since to reimage it to see if it changed but the weather has made a mess of all attempts. Now with it being over a month later and the moon in the area, I went through all the attempts and found one that was sort of usable. Seeing was poor by comparison so stars are much larger. This makes them appear brighter but I've actually processed them virtually the same. The difference is just due to seeing and changes in transparency. The second attempt was taken September 23 so 6 days shy of a month later. Two differences are obvious. First it has changed color. This was rather expected. Many nova (but not the previous nova in Delphinus in 1967) blow out huge shells of hydrogen gas that glows in typical hydrogen alpha red and weaker hydrogen beta blue-green. Since the red dominates the star appears to turn red though it is actually the as yet unresolved hydrogen shell it expelled that gives it the red color. The star is still blue hot from the eruption. The other change, also as expected (but again not the case with the 1967 nova in Delphinus) is that it has gotten fainter. I've included a side by side comparison as well as the full frame from September. Both the August and September images were taken precisely the same way in order to try and preserve comparability. I should add that while the nova appears to have a red halo about it that is just glare from the star being so bright. This is the same as the blue glare around the earlier image but colored by the H alpha shell. The actual hydrogen shell is still an unresolved point source same as the star itself. 14" LX200R @ f/10, RGB=1x10' each, STL-11000XM, Paramount ME Rick -- Prefix is correct. Domain is arvig dot net |
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