From: Milton Aupperle <milton@outcastsoft.com>

Date: April 22, 2005 4:23:49 PM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Alignment

Hi Alan;

On 22-Apr-05, at 3:40 PM, Alan Friedman wrote:

Hi Milton -

From the images, the new version seems to be a real improvement.

The sharper your edges - the better it will work.

Having no idea what is involved in writing a complex piece of software, would it not be possible to have a user interface to the fine alignment routine? Drawing a selection box, or at least positioning the box if the dimensions are to be a set size.

Picking an edge manually probably wouldn't help much, as what you perceive as a feature may not exist, especially since I first convert the image to monochrome before processing to reduce the color and other noise issues. I also do a lot of upper and lower limit filtering (mean, median mode STD based) too to make the centroid calculation more precise.

I get such different results depending on what section I choose for alignment - I can't imagine not having this option.

I'd have to think about it - as it means breaking the process flow up and I really want an automated tool for batch processing and stacking.

Two other quick questions -

what is a centroid?

A centroid is basically the weighted X,Y center of an area.

http://www.efunda.com/math/areas/Centroid.cfm

Commonly you use the pixel intensity for the mass of the object..

what does HTH stand for?

HTH = Hope That Helps..

Milton J. Aupperle

President

ASC - Aupperle Services and Contracting

Mac Software (Drivers, Components and Application) Specialist

#1005 - 815 14th Avenue. S.W.

Calgary Alberta Canada T2R0N5

1-(403)-229-9456

milton@outcastsoft.com