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Can anyone help with stars...

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I am wanting to make an action for a specific routine.

I want to create an action in photoshop that will remove the stars from the image and put them on a second layer.

So you will be left with an image with a layer with no stars just the background and DSO and another layer with just the stars on.

I know how to create actions its more of how to do the above.

Does anyone have an action they could post up or indeed explain what steps would be needed to create the above action.

I think I have the removing the stars from an image bit, its more of how to move the stars to another layer.

Can anyone help?



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I have an action in my set that does this (just fyi) and I have gotten several requests for a video showing how which is already in the works.

Depending on how slow my internet is tomorrow I should hopefully have that tutorial up and you can use the steps to create your own action if you wish.

The video will be posted at Enterprise Astrophotography: Shooting the stars | Videos ... If I can't get the video up I will at least post the steps for you

Edited by antimorris

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Thats great, thanks Anna, I will keep my eye on the web page



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It is so quick and simple to do you do not really need an action. Apart from anything else you need to set a selection value and then modify the subsequent selection so the action would have to keep stopping while you 'adjust' it.

Try this:

1. Assuming you are starting with a single layer, duplicate the layer. (Drag it to the new layer icon in the layers palette).

2. Set the layer to Threshold, Image - Adjustments - Threshold.

3. Adjust the slider until most of the stars are selected. OK.

4. You sometimes pick up bits of galaxy or nebula, just switch to Quick Mask and using white as the foreground colour select the Brush tool SET TO 100% HARDNESS and de-select the bits you do not want selected.

5. Use the Magic Wand with a low tolerance (4) and select the background.

Remember; you can always use another duplicate layer and stretch it unreasonably just to help make the selection. Then delete that layer.

6. Invert the Selection, you now have just the stars.

7. Save the selection if you want to use it again.

8. Delete the Threshold layer

9. Expand the selection by a small amount, say 1-2 pixels depending on the sharpness of the stars. You MUST select some background to the star at this stage.

10. Feather by 1 pixel.

11. With the background the active layer do a Ctrl J to make the star layer. The selection outline will automatically disappear.

12. You can now duplicate the background and set to Overlay to do a High Pass on the nebula without affecting the stars. Then flatten.

It can be very inadvisable to do anything else to the picture whilst it is in layers.

With practice you can do all of the above very quickly. Often it requires no intervention by you to clean up the selection. I can do this much quicker than you can read the above. Although it is not a race that might give you some idea of how simple it all is.

Do not do unnecessary work on the picture while it is in layers. Did I already say that?


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My video capture software is having a few bugs so until I get it sorted here are the basics. As Dennis showed you can do it via the Threshold adjustment, however if you are willing to spend a little more time I have found that the "Dust & Scratches" filter allows a bit more accurate layers so you can work on them a bit better separately.

Here are the basic steps:

1. Duplicate your Background Layer

2. Run "Dust and Scratches" (Filter->Noise->Dust & Scratches) ... I find that a good starting point is a radius of 26-28 and Threshold of 16-19. You want to make sure you don't blur out any detail of your DSO, just the majority of the stars. Its ok at this point if you have some star remnants left

3. Run a few more iterations of Dust & Scratches, each time halving both the radius and threshold until you get to a radius of 1-2.

4. At this point you will have most of the stars removed, though you are likely to have some remnants. You will use the Healing Brush Tool to clone them out - this is the part that is time consuming as the more accurate you are here the better your final result will be. Make sure when you are cloning the remnants that you select an area as close as possible and that you don't add or remove any detail to your DSO (i.e. if the star was in nebula make sure you clone the same portion of nebula and likewise if it was just on the background)

5. Once you have your completely starless layer duplicate it as well as your original background. You should now have 4 layers, order them thus: Starless, starless copy, background copy, background. Select the "Starless copy" and set its Blending mode to "Difference" then merge it with the "background copy" - the result is your "Star layer"

6. You will now have your starless layer, your star layer, and your original background and you can work on them as you wish.

Hope this helps. I do hope to have the video still up soon once I sort out the Lion OS incompatibility.


Edited by antimorris

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Many thanks to you both, I will have a play.



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