Drizzle Integration

rjbokleman

Active member
Dec 14, 2015
32
0
www.astrobin.com
It's been awhile since I processed an image, but I'm working with 01.08.06.1475 and was going through the rather normal motions of:
  • Cosmetic Correction - Each filter into its own folder ...\CC
  • Subframe Selection - (Using the new tool and I like it over the script before.  Much easier!) Each filter into its own folder ...\SFS
  • Star Alignment -  Each filter into its own folder ...\R, using Generate Drizzle Data to the same ...\R folder.
  • Local Normalization - Each filter has it's best reference image selected from the ...\R folder, all the ...\R folder images for that filter selected, and the output also going to the ...\R folder such that each image now has its .xisf, .xnml and xdrz files ALL in the ...\R folder per filter.
When I ran the Drizzle Integration, however, the Process Window is showing me that's it appears to be pulling the .xisf from the ...\SFS folder instead of where I thought it would...which should be the ...\R folder where the registered/star aligned .xisf file actually lives.

Anyone see this as a problem, bug or did I just do something wrong with my LocalNormalization?
 

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John_Gill

Well-known member
Hi,

I cannot help with your file structure.  Perhaps reprocess and check each folder for the resultant images and the file name change.  As a side note.... I have read many "bad" reports about LocalNormalization.  Mostly people say you should not use this process unless you know exactly how, what and when to use it.

space is not black
John
 

Juan Conejero

PixInsight Staff
Sep 2, 2004
8,129
334
57
Valencia, Spain
pixinsight.com
What you describe is perfectly normal behavior. Drizzle integration uses exclusively calibrated data, i.e. pre-registered, non-interpolated data. If you have implemented all preprocessing tasks correctly, the geometric transformations necessary for image registration, along with statistical data and pixel rejection data, have already been stored in the .xdrz files that you load from the DrizzleIntegration tool. The drizzle algorithm reads the original calibrated pixels and re-projects them on a finer grid.

I strongly recommend you to read the original paper by Fruchter and Hook, where the drizzle algorithm was first described:

https://www.researchgate.net/publication/1840344_Drizzle_A_Method_for_the_Linear_Reconstruction_of_Undersampled_Images

In our implementation of drizzle, the registered frames, as well as the output of the ImageIntegration tool, are all temporary data necessary to update .xdrz files.

As for LocalNormalization:

- Please do not use it on a regular basis, unless you have good reasons to use it (mainly gradients with varying orientations).

- Please do not use it on dissimilar images. For example, don't use LN on narrowband and wideband images. This simly does not make any sense.

- Always inspect the resulting images after LN. The LN task is ill-posed by nature, so never take for granted that the implemented algorithms will succeed. The LocalNormalization tool provides many resources for quantitative and qualitative evaluation of results.