Alignment Issue

[mick pinner]

when doing a core layering for M42 in Photshop is there a particular way of aligning the 2 images before pasting the short exposure onto the long exposure? l think this is the misalignment issue some people have mentioned in my recent images. thanks.

[Omaroo (Chris Malikoff)]

Mick - whenever I'm aligning frames that I've pulled into Photoshop and that reside on separate layers, I usually use guides to help me. While showing just the base layer, I pull both horizontal and vertical guides in to intersect a bright star at the top left of the image and then repeat for a star at bottom right. In your layers palette, deselect the base layer view and select the next layer. With the Move tool selected, tweak its position until the same two stars are intersected by the guides. If you flick back and forth between the layers being viewed they should all line up with the chosen intersected stars. Maybe view it at 100% to be more accurate.

When you have all the layers aligned manually this way (as long as you haven't suffered rotation - which is a bit more complex to fix) you can convert the layers to a Smart Object (if you have CS3 or newer) by right-clicking in the layers palette and then choose the appropriate stack mode from the Layers/Smart Objects/Stack Mode menu. I usually use "mean" stacking here.

Does this help or am I missing your intention?

[sheeny (Al)]

Mick,

What version of Photoshop are you using? If CS3, have you tried the automatic process for stacking?

It's under Files, then either Batch or Scripts... something like Stack Images it's called (I don't have access to PS ATM so I'm forced to make it up as I go along - that should inspire confidence!). In the dialog there is a check box for "align frames based on content".

I have used that with some success. The key is if there is enough that PS recognises as the same between the frames, so it may not work on radically different exposures.

Al.

[Omaroo (Chris Malikoff)]

If you haven't tried it before Mick, and you have CS3, then try this method! I've had it working, like Al, quite successfully in a few instances.

This is the way to get there if you intend to start at that point. File/Scripts/Load Files into Stack" is the menu item. Auto-alignment rarely works very well, so you usually have to split the stacked Smart Object back into layers anyway, do what I did in the post above to manually align, and then re-combine the layers back into a Smart Object and set the stack mode.

[sheeny (Al)]

Thanks for the translation, Chris!

Al.

[Geoff45 (Geoff)]

The other thing which works is to use ImagesPlus (and I presume other astro software) to produce two aligned pics and then paste them separately as layers in PS.

[multiweb (Marc)]

Originally Posted by mick pinner

when doing a core layering for M42 in Photshop is there a particular way of aligning the 2 images before pasting the short exposure onto the long exposure? l think this is the misalignment issue some people have mentioned in my recent images. thanks.

Hi Mick, depending on the PS version you can use Photomerge which will align your pictures and split them on different layers. Its prime use is to mosaic regardless of the amount of overlapping. Just delete manually the opacity mask it generates and make your own and blend "to taste".