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Cone Nebula HaHaRGB

MartinB

By MartinB
in Imaging - Deep Sky

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MartinB

MartinB

Posted
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A little to the NNE of the Rosette this is a busy bit of sky full of emission and dark nebulosity along with a the pretty little Christmas Tree cluster which is a nice visual target. I wanted to show the blue reflection nebulosity within the Ha along with the wonderful Ha convolutions.

It was very interesting to process since there are so many different features to home in on. The disturbed area below the base of the Christmas tree is known as the fox fur nebula and shows up best when the contrast is cranked up a little but this tends to detract from the great patterns in the background where Ha mixes with dark nebulosity.

If I had hours of imaging time to spare I would go deeper so that some dust detail would start to emerge but that wasn't the aim for this one.

Scope: FSQ 106

Camera: QSI 532 guided with Lodestar and ZS66

Filters: Baader 7nm Ha and Astronomic type II RGB

Mount Tak EM200

Exposures: Ha 6x1200 secs Red and green both 9x 180 secs unbinned. Blue 9x300 secs

Calibration: 100 bias, 50 flats for each channel and 20 darks for each exposure length

Captured with Maxim DL V5. Debloomed and calibrated in Maxim. Registered, normalised and combined in CCD stack and completed in PS

I was a bit short on colour data but was please to pull some of the blue reflection nebulosity into view - using the softlight blend mode to enhance colour saturation worked very well here.

post-12794-133877417252_thumb.jpg

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RobH

RobH

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That's the best image I've ever seen of the area Martin :hello2::hello2::)

The RGB really works well. Your stars are lovely and tight, with great colour.

How did you stop the Ha luminance from dimming the colour in your stars?

Hats off to you :)

Fantastic work sir.

Cheers

Rob

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MartinB

MartinB

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Thanks everyone

Rob - in the past I have tried taking a star layer from the RGB and putting it over the Ha. It often doesn't work all that well since it's difficult to blend in smoothly. I tried a different technique this time. I left quite a pedestal below the black point on the RGB, this brightens the whole image as well as leaving a lot of room for manouevre.

I put a duplicate RGB above the background and then the red Ha. The Ha blend is lighten as usual but the duplicate RGB uses soft light, this darkens the background but slightly brightens the brighter areas. It seems to help punch the non Ha colour through the Ha layer.

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SteveL

SteveL

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I put a duplicate RGB above the background and then the red Ha. The Ha blend is lighten as usual but the duplicate RGB uses soft light, this darkens the background but slightly brightens the brighter areas. It seems to help punch the non Ha colour through the Ha layer.

/me writes that down for later use....

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narrowbandpaul

narrowbandpaul

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very nice image martin....

i hope you dont mind but there is an alternative method for combining the Ha data (well there are several)

the ha being used for luminance will attenuate any colour data that isnt also present in the luminance....think of it as a logical AND operation...

an alternative is to use R=Ha+R G=G B=B+0.3*Ha to mimick the Hbeta....

i dont know how much it will change the image, but if you have some time on your hands...

I suppose L=R+G+B......

but the luminance needs to contain all wavelengths present in the colour data, so using Ha means only the red data will satisfy this criterion.

paul....

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MartinB

MartinB

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You're absolutely right Paul. This is very easy to confirm. If you make 3 circles in an image in PS and fill them with RG and B but create a grey scale image from the red circle only then use that as a luminence only the red will show through.

I added the Ha to the red channel using lighten mode and did the same with the blue channel but at 20% opacity. All the advice I've read is to do this, then combine then stretch, however it never seems that much of the Ha data is retained hence adding in a processed Ha layer later on. I have tried in the past adding stretched Ha to the stretched red and blue channels but you still get problems with the Ha dominating. I think this problem of getting the other colours to show in an HaHaRGB image is quite a challenge!

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