Spokes in Helix LRGB image

[sjastro]

I'm not a fan of narrowband imaging but details that are readily visible in narrowband images are generally not so obvious in LRGB, even if narrowband filters are used for luminance.

I'm fairly pleased to have preserved the OIII spokes in this L=Ha+OIII RGB image.
The spokes are lost in the combined luminance if the images are normally processed.

Details
L=10 hrs OIII+ 6hrs Ha, 1 hr each RGB.
BRC-250 scope, STXL-11002.

High resolution.
http://members.iinet.net.au/~sjastro/ngc7293sp.jpg

Comments welcome.

Steven

[Geoff45]

Really nice Steven. Lots of interesting detail in the core and you've done a good job with the colour. It's not obviously a narrowband image.
Geoff

[Ryderscope]

Agreed with the nice structure that you have managed to capture in the core Steve. I am envious of that BRC-250 scope I have to say. Thanks for posting.
R

[rustigsmed]

awesome Steven, the Oiii is super interesting in the Helix. spokey dokes. I hope to get a good version of it this season. thanks for sharing.

cheers

[gregbradley]

That's a great rendition of the Helix Steven. Nicely done and a very interesting aspect of the Helix.

Greg.

[sjastro]

Thanks Greg.



It will be interesting to see your results Russell.



It's a fine scope Rodney and fits well in the region between low and high focal length imaging.



Thanks Geoff.
A test of the processing routine is to compare the image to the narrowband version (Ha, OIII, OIII).
The spoke structure compares more than favourably.

Clear skies to all.

Steven

[alpal]

Fantastic image Steven,
that BRC-250 is really sharp.

cheers
Allan

[sjastro]

Thanks Allan.

Steven

[sjastro]

The LRGB has more contrast and less noise than the narrowband version.

Steven

[RickS]

The spokey version is a nice, fresh view of this target. Well done, Steven.

[sjastro]

Thanks Rick.

It's possible to image in LRGB in the same detail as narrowband, without the psychedelic vibrant colours.

Clear skies

Steven

[astronobob]

Ripper seeing them spokes Steven, great version & dig the smooth result too !!

[sjastro]

Thanks Bob.

Steven

[Bassnut]

Yes, the spokes are oft lost, well processed.

[sjastro]

Thanks Fred.

Steven

[Shiraz]

nice work Steven. the spokes appear to me to be shadows from inner structure. They show up mainly in O3, so I guess that could mean that the shadowing gets rid of the hard UV, leaving the softer UV to excite the outer hydrogen. Does that make sense?

[sjastro]

Thanks Ray.

The process is poorly understood but the termination of the fast stellar wind is believed to create such intricate structures.
Here is a paper (http://arxiv.org/pdf/astro-ph/0606205v1.pdf) that explains the effect.

Regards

Steven

[Shiraz]

thanks very much for that paper Steven. As you showed in your earlier thread, the spoke pattern is almost not there at Ha, but strong at O3 - spectral issues are not addressed in the paper, but I guess it could possibly be that the follow-up wind has more O3 than the initial shell. It is really interesting trying to understand (even if on a superficial level) exactly what is going on in our images. Will definitely have to do some more reading on Helix.

[sjastro]

Ray,

OIII is a forbidden line emission and has never been reproduced in laboratories, since the very best laboratory vacuums are teeming with particles which de-excite the O atoms through collisions.
By comparison the vacuum of interstellar space allows OIII emissions to last much longer.

I suppose the stellar winds which are driving the expansion of matter into space resulting in decreasing density with time, leads to the highly rarefied conditions where the OIII emissions can exist for long periods.
Maybe it explains the dark lanes in the image which are devoid of matter:).

I'll will also be trying to gain a better knowledge of the subject.

Regards

Steven