Ngc4945

[TrevorW]

Top image gets my vote

[gregbradley]

Nice tip Jase.

I'll drill that and start using it myself.

Cheers,

Greg.

Originally Posted by jase

A very tidy image Stuart. Excellent details and great colour. The image doesn't have a heavily processed feel which is pleasing. Composition is a little odd being offset, but I suspect this may have been the result of finding an ideal guide star for the AO kit - trade off.

You can do as Greg mentions to remove the blue flare from the background, but in my experience you'll find the method is tedious given you only want to manipulate the sky background and not impact the stars in the region. Its also complex when using curves to drop a hue and not cause imbalance to the surrounding feathered area.

Here is my preferred method to detailing with such background colour flares from pesky stars off the edge of the frame. It can also be used to repair other issues. For example, in the recent Rho image I posted, the star halo reflections were are bright green. I simply used this technique to address them. Its a little more involved, but the result is very accurate.

• Click on the lasso tool and set the feathering to approx 20 pixels
• Using the lasso tool, select an area that is of same size and is relatively close to the colour flare area you wish to remove. The purpose of this exercise is to match the background hue of the surrounding area so the proximity to the area you're trying to fix is fairly important. At this point, don't worry if the selected area contains stars.
• Copy and paste the lasso area so you now have a new layer that contains the small patch of the sky in which you've just copied.
• Hold down the control key and move the mouse to shift the small patch over the colour flare area you wish to remove.
• Now go to the Filters | Noise | Median
• Increase the radius until you see no more stars in the small patch of sky that you've copied. If you don't like the median tool, dust and scratches, or the minimum filters can do a similar job. Median I've found works well in general.
• With the patch layer selected, change its blend mode from normal to colour
• You'll now notice that your colour flare has disappeared i.e. has been blending into the surrounding background hues. If it hasn't you may need to increase your selection size or reduce the feather.

...but don't stop there...look what you've done to the stars in the area that's been repaired...they've inherited the same background tone you copied. Easily fixed...

• Select the original layer and use the colour range tool to highlight the stars. Alter the fuzziness slider until you get a good match.
• Expand the selection by 2 or 3 pixels (or to your taste)
• Feather by 2 pixels (or to your taste)
• Then select the patch layer (important, make sure its selected!!)
• Hit the delete key
• POW! You've now brought the star colours back in the repaired area...as you've deleted the selections from the patch layer so the colours come back through from the original layer.
• If you find that the colour range tool selection wasn't ideal, you can always use the eraser tool to do a similar task, but I would recommend going back a few steps until you get the right selection i.e. manipulate fuzziness.

Give it a try! Should probably have posted this in the photoshop tips section. May put a cross reference to it somehow.

Cheers

[Alchemy (Clive)]

very impressive detail in the galaxy,

when i go to save the image a little warning pops up about the copyright ( as always) i only redistributed it to my hard drive , a keeper for my collection.

clive

[rat156]

I've added the reprocessed image according to Jase's instructions, certainly has gotten rid of the blueness to the flare. As It's still there in the Luminance channel the streaks are still there, but they are there on the other side of the galaxy as well...

Cheers
Stuart

[jase (Jason)]

I've come back to check your work out again a few times. Really like the detail you've obtained. The recent adjustment has certain reduced the distraction. I don't think I'd probably worry about the luminance flare... I guess this is a case of how far you want to take it. With the flare colour gone, you could follow up on the luminance with the following. Its similar to what I advised previously to bring back the star colours (just leave the layers as a normal blend this time).

• Duplicate the luminance layer and select the new layer
• Go to the Filters | Noise | Median
• Increase the radius until you see no more flare in the luminance. Its ok to blur it relatively hard as you can dial back the adjustment later using the opacity settings or a mask. The goal should be to get rid of it so do what it takes to get that far.
• Select the original luminance layer again and use the colour range tool to highlight the stars including the galaxy. The stars are more important at this stage so focus on these. Alter the fuzziness slider until you get a good match. Make sure you get those faint ones (a high fuzziness setting).
• Expand the selection by 2 or 3 pixels (or to your taste)
• Feather by 2 pixels (or to your taste)
• Check the galaxy selection and adjust Get the lasso tool out (shortcut L) (feather by 20 pixels or so) and add to the current selection (hold down the shift key to add to selection). Lasso the galaxy so you've got the out reaching arms highlighted.
• Recheck the selections. If you find that some of the flare is also selected, subtract it from the selection using the Alt key with the lasso tool.
• Then select the duplicated layer that you've performed a median filter on (important, make sure its selected!!)
• Hit the delete key
• DONE!
• The galaxy and stars are brought through the original luminance layer, while the background in which has had median filter applied is taken from the layer above.

You'll probably find that the background will now look too smooth and noise free. While in some cases this is ok, but you want to avoid the plastic feel, a bit of noise is good. You can dial back the opacity a little OR, what I normally like to do is create a hide all layer mask on the duplicated layer. Then you can use a paint brush to paint the mask to reveal the median filtered luminance background on the affected areas. You can't impact the stars as they've already been removed from the layer. Just dial back the brush opacity and flow (20/20 works well for both settings), but its a matter of preference.

You can do a similar task using an inverse mask, however you'll find that the mask itself may also contain the flare in which you're trying to remove so you'd need to modify it before hand. Of course, theres more than one way to do the same thing in PS. Its just a matter of finding something that works well for you. Hope it helps.

Cheers