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Old October 14th 13, 10:53 PM posted to alt.binaries.pictures.astro
Stefan Lilge
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Default 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
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