What is the "right" colour?

[cybereye (Mario)]

Hello everyone!!

Having read an article in the latest Astronomy magazine, coupled with the images seen in this thread I was wondering on what colours nebulae should be? I'm sure asking this is like asking the proverbial "how long is a piece of string?" question but it's something I'm struggling with at the moment.

I know in theory emission nebulae should be red and reflection nebulae blue, but other than that what would people consider the correct shades? I've read contradictory advice to the shade of red for emission nebulae - everything from blood-red (because of the Ha in the near infra-red wavelengths) to magenta (because of the inclusion of Hb in the mix).

Do we really know what the true colour is or do we aim to make something that's pleasing to the eye that gives as much detail as possible?

Obviously I'm talking about RGB/OSC images here and not the Hubble palette and I'm very interested to get people's take on this issue..

Cheers,
Mario

[strongmanmike (Michael)]

Yes, many armchair experts out there on this one, asking this question is like asking how should we tackle climate change = never ending argument.

I think what you said is almost correct though, basically Emission nebulae are various shades of magenta with a couple of redder ones out there, reflection nebulae are some shade of grey-blue with some teal/turquoise thrown in....then there is the dreaded saturation .....

What are considered acceptable colours in imaging varies with trends too, this is particularly the case in emission line narrowband imaging, we can be flock like at times....Mission Brown will make a come back, I'm certain, if a couple of famous imagers manage to get it out there.

In the end, what is pleasing to one eye may not be so much to another....so keep'em black and white if you are scared to offer an option.

All good fun in the end

Mike

[marc4darkskies (Marcus)]

Hi Mario!

IMO, when you're processing RGB master, whatever the colour ends up at once you've got the star colours right (some use G2V calibration for this) is the closest you'll probably get. Blending Ha to RGB is where you'll get the black arts coming in. But if you make sure it doesn't depart toooo far from the colours in your RGB you're OK - it's easy to let your Ha overwhelm the brighter parts of the neb. It's usually only the fainter Ha signal I make deep red but some personal preferrence always prevails.

Cheers, Marcus

PS: Even though you're talking about OSC, you should still first calibrate on star colours and use that version as a reference point while you're doing your enhancement processing.

[Terry B]

This isn't really an answer but take a look at my spectra of an emision nebula here
http://www.iceinspace.com.au/forum/s...ad.php?t=94818
My image of M8 has pretty poor colour balance but it was only made as an identification pic. The spectra shows narrow lines only. How these mix is really up to you and probably everyones eyes will mix them slightly differently.