Author Topic: How to use Dynamic Aligment to register a non-astro image to an astro image?  (Read 1518 times)

Offline marekc

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Hi Everyone,

I'm trying to make an `overlay map' to put on an image of M31. I shot M31, and processed it in PI, and I'm pleased with the result. I would like to overlay an isophote map published by some professional astronomers. The isophote map is basically a drawing consisting of a bunch of lines.

I have the isophote map as a PDF, and I can re-save it in pretty much any format required, using Photoshop. I can even use PS to do some basic scaling, rotation, etc... I could use PS to invert it, and remove the background, so that it would just consist of glowing white lines on a transparent background - perfect for overlaying onto my image. But, I need to be able to pick corresponding `control points' on each image, and distort the overlay to match my M31 image.

Photoshop has a `Warp' tool, which sort of works, but doesn't work as well as I'd like. The isophote map has a number of stars marked on it, and I'd like to get those marked stars to `drop onto' my stars with a reasonably high degree of accuracy.

All of this reminds me a lot of Dynamic Alignment. I see that I can choose an `inverted' registration point, but that isn't doing what I want. My main problem is that the control points keep `snapping' to certain features in the target image. I try to put the target-image version of the control point on a particular feature, but Dynamic Aligment keeps saying `no, no, I've detected a feature over HERE! This is where I want to put the control point!'

This makes perfect sense, of course, since Dynamic Aligment is very good at finding stars, which is what it's designed to do. But I wish I could invoke a `manual override', so that I could set the `target' version of the control point wherever I want. Does anyone know if this is possible?

I've tried to find other software to do this kind of thing, without much success. Panorama-stitchers like Hugin don't seem to do what I need. Photoshop's `Warp' tool is too much of a blunt instrument. Dynamic Alignment seems to have the power that I need, but it seems to be designed to work with stars, and I just can't place the points where I need them, unless there's something I'm missing.


- Marek Cichanski