Quite amazing that two lines so close together give such a different view.
And a very nice picture btw.

Stefan

"Richard Crisp" schrieb im Newsbeitrag
...
the Custom Scientific 3nm FWHM filters were confirmed tonight to split the
very close emission lines of the [NII] doublet at 658.4 nm and the Halpha
line at 656.4 nm.

I used the 450mm f/12.6 classical cassegrain with the Lumicon GEG reducer
in the rearmost position for an effective focal ratio of f/7.1

Exposures were 20 minutes binned 2x2 using the FLI Maxcam10 at 3366mm
focal length (0.84 arc-sec/pixel)

It is clear that the filters will in fact separate those two very closely
spaced emission lines.