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Okay, I give up. Can you set an arbitrary rotation point? I've got 32 layers of an astrophotograph and to align them, I need to rotate them individually around a specific point.

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Hi tharper,

 

and welcome here …  :)

 

You can indeed set a custom rotation center. Select the Move Tool, activate the layer you want to rotate, and tick the Show Rotation Center button on the context toolbar. Now the rotation center gets visible and you can move or snap it to any position you like. But please note, that you currently cannot use the Transform panel with a custom rotation center. You have to use the bounding box handle to rotate your layer on-canvas.

 

Hope that helps …  :)

Alex

post-1198-0-67357200-1450123409_thumb.png

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I am not familiar with astrophotographs but I can pick up on the graphics dilemma you're in, sort of. Can you provide a little more detail on your setup and what you end goal output should be? This doesn't sound too terribly difficult to solve.

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Maybe it's with trying the stacking option because AP can auto align images

 

You can then switch to "scale and rotate" or "perspective" and scale and rotate should give you pretty much the same result you'd get manually ...


 

 

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Ideally auto align would be the bomb, but it's hit or miss on astrophotos; the scene is dark and stars are tiny. The situation is this, the camera is locked down but this damn planet rotates at just over 1000 MPH at the equator (I'm in Costa Rica, 9° north of the equator). In this case, my shutter is open for 4 seconds, then there's a 6 second break, then another shot at 4 seconds and so on up to 32 shots. You then want to align and stack those images and use the mean filter to eliminate noise (because you're shooting at a high ISO). Are ya with me? I've got a jpeg of my first and last frame blended, the rotation is obvious, but I can't seem to get it into this post.

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I think you want to create star track images?

It might also be difficult to align them with stacks if there are only moving stars and no constant foreground.

 

As I think there´s no 100% automated solution for star tracks yet in AP.

 

But I can say that noise reduction through stacks is a beast :) 


 

 

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Hm but if the earth moves and you want to fix it through rotation only, I'd say that you also have to transform it in x and y position?

Or do you line up the centre star first and then rotate around it to match the rest?

Well you seem to be the expert and my suggestions may not work in this situation, sorry.


 

 

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Hi tharper,

 

To add an image to your post, click the More Reply Options button below, and follow the instructions on the page that is linked.

 

What regards your question, well, you can “sort of” work at a hundred percent zoom with a custom rotation center. If you have a mouse and a trackpad (or a mouse with a scroll wheel), you can activate the rotation cursor by clicking the rotation handle of the layer’s bounding box and then, while the mouse button is still depressed, use the pinch gesture on the trackpad (or the scroll wheel of your mouse) to zoom in. But that is very cumbersome.

 

So here’s another technique, essentially due to evtonic03 and Gear maker (see following posts), and this technique does not make use of translating rotation points:

  • Locate the star, you want to use as the rotation center for your layer.
  • Choose the Ellipse Tool from the tool bar, hold down Shift and Command, click on the canvas position of this star and drag out a circle around it, such that the whole layer, that you want to rotate, is enclosed within that circle.
  • Set the created circle transparent and group your layer with the circle.
  • Now select this group, go to the Transform Panel, set the Transform Panel rotation center to the mid point there, and use the slider to rotate your group around the chosen star.
  • The big advantage is, that you can use the slider of the Transform Panel at any zoom level.

That should work … see my video below …  :)

Kind regards, Alex

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Hi tharper,

 

To add an image to your post, click the More Reply Options button below, and follow the instructions on the page that is linked.

 

What regards your question, well, you can “sort of” work at a hundred percent zoom with a custom rotation center. If you have a mouse and a trackpad (or a mouse with a scroll wheel), you can activate the rotation cursor by clicking the rotation handle of the layer’s bounding box and then, while the mouse button is still depressed, use the pinch gesture on the trackpad (or the scroll wheel of your mouse) to zoom in. But that is very cumbersome.

 

So here’s another technique, essentially due to Gearmaker, another forum member, and this technique does not make use of translating rotation points:

  • Locate the star, you want to use as the rotation center for your layer.
  • Choose the Ellipse Tool from the tool bar, hold down Shift and Command, click on the canvas position of this star and drag out a circle around it, such that the whole layer, that you want to rotate, is enclosed within that circle.
  • Set the created circle transparent and group your layer with the circle.
  • Now select this group, go to the Transform Panel, set the Transform Panel rotation center to the mid point there, and use the slider to rotate your group around the chosen star.
  • The big advantage is, that you can use the slider of the Transform Panel at any zoom level.

That should work … see my video below …  :)

Kind regards, Alex

 
Not sure if I like Gearmaker getting credit for this solution! I posted the same thing in video here! LOL
 

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