Re: [APML] Widefield Comet Machholz

Thanks Carlos, I will be working on it.

Gary

----- Original Message -----

From: Carlos Milovic F.

To: Discussion of Film Astrophotography

Sent: Monday, January 31, 2005 2:08 AM

Subject: Re: [APML] Widefield Comet Machholz

It isn't as complex as you may think. Each layer contains features of certain characteristical scales, wich are very related to the pixel scale that is shown. It depends critically with the scaling function you use. If you are familiar with convolutions (user defined kernels, or maks), you can think on the first layer just like a high-passed version of the image, made with the same principles of the unsharp mask, but using the scaling function as a bluring convolution. To create the other layers, you make new high passed version of the image from the result of deleting all the small scale features you just isolated in the first layer (so, now you have a blured images as a remannent, called "residual image"), and so on.

So, in practical words, we can think on every layer as a subimage containing all the features of the original image at certain scales, plus a last layer with the residual image. The final image is builded just by adding each processed (smoothed, biased, etc.) layer to the residual image.

You just have to keep in mind the the way the features are separated into those layers is in direct relation with the scaling function. If it looks very sharp, you can isolate high frecuency features very well (for planetary images, for example). In the other hand, big and plain functions will play a great role if you want to enhance large scale features. Keep in mind that you can manage the functions just like if they were convolution filters, modifying them, creating new ones, etc.

Regards,

Carlos Milovic F.
-------------------------
Astro & Photo - CMF
http://www.astrophoto.vze.com
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Visita "AstroFoto", el foro de astrofotografía en español
http://espanol.groups.yahoo.com/group/astrofoto

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