Hi, Robert.
The issue is taking off, it seems. Good to see that it's interesting enough. In any case, it appears to be a "take it easy, don't hurry" theme.
I've started a list of pertaining DSO objects. It's more complicated than I thought; Up to now, I only have objects that I've tried to image:
Supernova remnants
match; imaged; Common name; Id; Const
√; √; Veils (Gygnus Loop); Sh 103; Cygnus
√; √; Crescent; NGC6888; Cygnus
√; √; Jellyfish; IC443; Gemini
?; √; Crab; M1; Taurus
Planetary nebulae
match; imaged; Common name; Id; Const
√; √; Ring; M57; Lyra
√; √; Dumbell; M27; Vulpecula
√; √; Little Dumbell; M76; Perseus
√; √;
no common name; NGC6781; Aquila
√; √;
no common name; NGC7048; Cygnus
√; √; Owl; M97; Ursa Major
?; √; Medusa; Abell 21; Gemini
In that list (sorry for the format), I'm not sure if M1 matches my, say, "hypothesis" (I have not enough susbs yet). I'd say the same about Abell 21, though the current "image in the making" seems to match too.
However, surfing the web, I've learned that planetary nebulae are (at least) of two kinds: bipolar, and non bipolar.
A paradigmatic bipolar example could be the
Twin Jet Nebula (just in my southern imaging border -a bit small for my scope and site-), Minkowski 2-9 (in Ophiuchus), and it's interesting because the distribution of the shells might match other PN in my list.
I've found a scientific paper on that PN:
http://iopscience.iop.org/0004-637X/..._552_2_685.pdf
But (in a quick fast reading -if one can do that with a scientific paper-) it does not describe the emission lines dominant in the shells.
Keep searching ...
The case of SNR it's tougher. Most google results point to multiwavelenght images, without enough details.
Keep searching ...