Managed to get an image of something I've wanted to have a go at for a while. This is vela supernova remnant taken from suburban Sydney (class 6 Bortle). This was done with a Canon 70-200mm L F4 lens at 70mm with an ASI 533 camera using (most importantly) an L-extreme dual band filter. A stack of 71 frames, 90s each. Unguided with NEQ6 mount. Auto stacked and adjusted in Sharpcap with a bit of extra processing in Photoshop.
The L-extreme filter lets through a narrow part of the light spectrum. It lets through the emissions from Hydrogen alpha which is part of the red end of the spectrum and OIII which is in the green part. The green in the image will be either OIII emissions which can get through unhindered (lots of OIII is a feature of this target) or 'stray' light e.g. I think a small fraction of the white light spectrum would come through (there is plenty of light pollution here) but it would appear either red or green.
For most targets there is very little OIII present and I don't get much green in those situations....
Very nice image Mark! Some nice detail there and beautiful colours. When colour calibrated correctly, the oxygen comes green-blue. Some photographers take the extra step of removing the green entirely. Artist’s prerogative though. All the same, you’ve produced a great image!
