Cassiopeia A

Supernova remnant in Cassiopeia.

This target is most difficult to capture and process.

I never realise how dim this really is. "Cartes Du Ciel" gives surface brightness

for this object as low as Mag 37 !

Fast optics, Tokina 300mm @ f2.8 helps to capture those few photons.

There is some internal structure details visible in S-II channel,

they can be seen in Hubble palette image as red.

More information in Wikipedia:

http://en.wikipedia.org/wiki/Cassiopeia_A

There is two version of this image here, first image is in "natural" color composition

from narrowband channels, H-alpha 100% + 35%S-II = RED, O-III = GREEN and

O-III 100% + 30%H-alpha = BLUE.

Second version is Hubble palette composition. S-II =RED, H-alpha = GREEN and O-III = BLUE

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Imaging data:
Camera, QHY8 -
Filters,
Baader 7nm H-alpha, Baader 8,5nm O-III and Baader 8nm S-II -
Optics,
Tokina AT-X 300mm @ f2.8 -
Exposures, 12X 1200s H-alpha, 1 X 1200 O-III and 6X1200s S-II + flats and bias
- Guiding, LX200 GPS 12" + PHD-guiding and Lodestar

Is there a outer burst in Cassiopeia A?

This starless image might show a hint of it.