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Orions Sword in 3nm NII

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#1 Bert


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Posted 13 December 2012 - 07:57 PM

Managed to get 10x16 minutes in 3nm NII of M42 and made a mosaic with the earlier Horse head data. There is a mismatch at the overlap but it gives an idea of what is possible.

Large image 5MB FoV 6.0 X 3.4 degrees.


I am finding that gradients are still a problem even with 3nm filters.


Astrograph is an Officina Stellare RH200 which has a focal length of 600mm and is F3, yes F3! Clear aperture is 200mm.
FLI Atlas Focuser.
FLI ten position filter wheel CFW-3-10 with 50mm square filters.
Astrodon E series LRGB and HA, NII, SII and OIII 3nm NB filters. Also a continuum filter 5nm.
Camera is a FLI PL16803 which has a sensor size 36.8 X 36.8 mm.
The FoV of this system is 3.5 X 3.5 degrees.
Mount is a Software Bisque PMX.

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#2 SL63 AMG


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Posted 13 December 2012 - 08:03 PM

That's amazing!

#3 Kildar13x


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Posted 13 December 2012 - 08:12 PM


#4 broca


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Posted 13 December 2012 - 08:40 PM

Amazing amount of dust you were able to capture and process out. Well done!

#5 psandelle



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Posted 13 December 2012 - 09:03 PM


Nice pic!


#6 rigel123


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Posted 13 December 2012 - 09:47 PM

That is simply unreal!! Amazing!

#7 David Pavlich

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Posted 13 December 2012 - 10:18 PM

That's a terrific image! :bow:


#8 freestar8n



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Posted 14 December 2012 - 08:30 AM


That's a nice image and it has potential, but I would be concerned that the mismatch is related to using 3nm at f/3 with wide field. Trying to separate Ha from Nii is fundamentally difficult with fast optics, and due to the large and variable angles through the filter, I would expect a variation in the ratio of Ha/Nii across the image. In a single image this wouldn't show much, even though it is present - but in a montage, any difference in this ratio would produce a mismatch.

I can't say for sure that is what is happening here, but some amount of variable mixing is inevitable across the image at fast f/ratio. I don't think there is a way to fully isolate Ha from Nii with fast optics - you either have to go wider band and combine them, or slower f/ratio to keep them separate.

This effect also may be related to your issue with gradients.


#9 Konihlav



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Posted 14 December 2012 - 10:38 AM

Bert - what a nice contrast :-) great!

Frank - I would not be afraid of F/3 and 3nm NII as the Astrodon filter is really ubercool (simply great!), but you are right that even that the Astrodon filters have very high transmittance and steep/narrow bandwith there probabably is some small % of Ha emission included in the image as the 658nm of NII in 3nm allows to pass light in between 656.5nm to 659.5nm in ideal case... and Ha is 656.3 if I am right... so the small % may be eventually 50% ;D who knows ;)

so good point! with slower scope it would be much better separated, but who cares in ORION ;D

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