ngc 281

[alacant]

Hi everyone. First have-to-think-a-bit image after full moon so I wanted to make it count. I still find it alarming the way in which the histogram shifts, even with a last quarter moon. Meridian flip at around 22:20 and moonrise an hour later, I managed some of this in darkness. Any comments, particularly on the CLS pallete scheme [1], most welcome. Thanks for looking, clear skies and please keep posting your images.

[1]As a dslr user, I don't think I qualify for pallete!

700d, 2 1/2 hours

[ebdons]

Hi, very nice image, lots of definition, stars look too colourful?, maybe too red/orange, could be the CLS, I use the Astronomic UHC, and mine comes out too green at the moment, although I'm just starting to get into OSC. keep up the good work! all the best Tony

[ollypenrice]

You do seem to get a distinctive colour bias. The blues are very cyan and so, it turns out, are the reds. Using selective colour in Ps I made these adjustments.

I also lowered the cyans in blue but forgot the screen grab. Sorry!

This gave the adjustment below.

Its rather more conventional but you may well prefer the original.

Olly

[alacant]

1 hour ago, ollypenrice said:

Its rather more conventional

Thanks for taking the time to adjust it. Much appreciated. I'm still not certain about colour balance and your method of using cmyk is a great idea. Must have a play with that.

OTOH, I'm still trying to get my head around all those blue and yellow (erm, 'alternative') renderings you see these days.

Anyway, no time to play atm as it's the two little nebulae close to gamma cassiopeiae tonight and we're fast losing daylight over here. Not good vibes for this one as I've a feeling it's gonna be another of another case of 'Alnitak taming'...

Clear skies...

[Starwiz]

Very nice!

[ollypenrice]

1 hour ago, alacant said:

 

OTOH, I'm still trying to get my head around all those blue and yellow (erm, 'alternative') renderings you see these days.

 

I don't really know what you mean here. There are essentially two kinds of colour imaging, 'natural colour' and 'colour mapping.' In natural colour imaging the idea is to get as close as possible to what a human super-eye would see. Because ionized hydrogen (at least the H alpha line) lies at the very limit of human perception, it will lift into visibility that which is not naturally so visible to the eye, but the imager can still try to respect the original colour balance while admittng the new signal. 

Colour mapping simply ascribes a particular colour to a particular gas, arbitrarily. It has no more to do with real colour than a geology map does, but it is informative. You could map with granite red, limestone green and sandstone blue - or any attribution you like.

Olly

[alacant]

4 hours ago, ollypenrice said:

You could map with granite red

Yeah, I need to think some more. I'm certainly contradicting my own idea on what colour should be by FWABW, 'CLS orange'!

[Starwiz]

4 hours ago, ollypenrice said:

Colour mapping simply ascribes a particular colour to a particular gas, arbitrarily. It has no more to do with real colour than a geology map does, but it is informative. You could map with granite red, limestone green and sandstone blue - or any attribution you like.

Is this what the so called 'Hubble Palette' does or is that achieved in a different way?

[ollypenrice]

9 hours ago, Starwiz said:

Is this what the so called 'Hubble Palette' does or is that achieved in a different way?

Yes, the Hubble palette maps Sulfur to red, Hydrogen to green and Oxygen to blue. Other professional observatories use a variety of different mappings.

Olly