Registration failure - what causes this?

[magnusl]

Hi!

I am trying to register a bunch of not perfectly guided images (I know, better guiding is a good thing), and my registration process fails. However, I don't understand why it fails - what tests are causing the error for some images? And if I wish to register these images - what should I adjust? (I'm having troubles registering all of my images, and this is an attempt to understand how to understand PI and to be able to tweak the settings). These are images of M57, with a lot of clearly visible stars, taken the same night with the same settings (no geometry issues or similar). I just don't understand why image 3 of this bunch of 3 fails, when the others work - they look very similar. And with 872 stars found - why is there not a match?

This is this output from the registration for one image that fails:

Registering target image 3 of 3
Loading target file:
/media/magnus/Elements/astrobilder/2015-11-15/M57_90sek/centred/lights_cal/Light_006_c.xisf
Loading image: w=5472 h=3648 n=3 RGB Float32
34 FITS keyword(s) extracted.
Structure map: done
Detecting stars: done
872 stars found.
Matching stars: done
342 putative star pair matches.
Performing RANSAC: done
* Previous attempt failed - this is try #2
useScaleDifferences=false
Matching stars: done
302 putative star pair matches.
Performing RANSAC: done
* Previous attempt failed - this is try #3
useScaleDifferences=true
* Reference image: Limiting to 250 brightest stars.
* Target image: Limiting to 250 brightest stars.
Matching stars: done
67 putative star pair matches.
Performing RANSAC: done
* Previous attempt failed - this is try #4
useScaleDifferences=false
* Reference image: Limiting to 250 brightest stars.
* Target image: Limiting to 250 brightest stars.
Matching stars: done
89 putative star pair matches.
Performing RANSAC: done
* Previous attempt failed - this is try #5
useScaleDifferences=true
* Reference image: Limiting to 125 brightest stars.
* Target image: Limiting to 125 brightest stars.
Matching stars: done
49 putative star pair matches.
Performing RANSAC: done
* Previous attempt failed - this is try #6
useScaleDifferences=false
* Reference image: Limiting to 125 brightest stars.
* Target image: Limiting to 125 brightest stars.
Matching stars: done
46 putative star pair matches.
Performing RANSAC: done
* Previous attempt failed - this is try #7
useScaleDifferences=true
* Reference image: Limiting to 60 brightest stars.
* Target image: Limiting to 60 brightest stars.
Matching stars: done
18 putative star pair matches.
Performing RANSAC: done
* Previous attempt failed - this is try #8
useScaleDifferences=false
* Reference image: Limiting to 60 brightest stars.
* Target image: Limiting to 60 brightest stars.
Matching stars: done
25 putative star pair matches.
Performing RANSAC: done
* Previous attempt failed - this is try #9
useScaleDifferences=true
* Reference image: Limiting to 30 brightest stars.
* Target image: Limiting to 30 brightest stars.
Matching stars: done
*** 0 star pair matches found - need at least six matched stars.
* Previous attempt failed - this is try #10
useScaleDifferences=false
* Reference image: Limiting to 30 brightest stars.
* Target image: Limiting to 30 brightest stars.
Matching stars: done
9 putative star pair matches.
Performing RANSAC: done
* Previous attempt failed - this is try #11
useScaleDifferences=true
* Reference image: Limiting to 15 brightest stars.
* Target image: Limiting to 15 brightest stars.
Matching stars: done
*** 0 star pair matches found - need at least six matched stars.
* Previous attempt failed - this is try #12
useScaleDifferences=false
* Reference image: Limiting to 15 brightest stars.
* Target image: Limiting to 15 brightest stars.
Matching stars: done
*** 0 star pair matches found - need at least six matched stars.
* Previous attempt failed - this is try #13
useScaleDifferences=true
* Reference image: Limiting to 8 brightest stars.
* Target image: Limiting to 8 brightest stars.
Matching stars: done
*** 0 star pair matches found - need at least six matched stars.
* Previous attempt failed - this is try #14
useScaleDifferences=false
* Reference image: Limiting to 8 brightest stars.
* Target image: Limiting to 8 brightest stars.
Matching stars: done
*** 0 star pair matches found - need at least six matched stars.
* Previous attempt failed - this is try #15
useScaleDifferences=true
* Reference image: Limiting to 500 brightest stars.
* Target image: Limiting to 500 brightest stars.
Matching stars: done
181 putative star pair matches.
Performing RANSAC: done
* Previous attempt failed - this is try #16
useScaleDifferences=false
* Reference image: Limiting to 500 brightest stars.
* Target image: Limiting to 500 brightest stars.
Matching stars: done
177 putative star pair matches.
Performing RANSAC: done
*** Error: Unable to find an initial set of putative star pair matches

[gvanhau]

Hello
It is difficult to answer WO a look to the images.
If could be that Hot pixels are recognized as stars.
You can tweak a litle the star detection parameters (roundnes) in order to facilitate the matching, however dont expect great ressults if stars are trailed.

Geert

[magnusl]

Hi!

Here is the image that the above output refers to. It's been crudely subjected to Histogram transformation just to show more stars, converted to png and scaled down. The original is CR2-file from Canon 70D.

For the moment, nothing is registered over here, no series that I have taken works with PI. I feel that there must be some setting that is off..... any ideas? Or are these stars not possible to work with for PI?

Magnus

[pfile]

under the star detection tab, you can try increasing the "peak response" setting, and perhaps try decreasing the sensitivity.

having said that your images are way out of focus which is why PI is not detecting any stars.

rob

[magnusl]

Hi!

If I understand the output correctly, it finds 872 stars in the first round......?

If it did not find any stars, I'd understand. If the focus (and guiding) is so bad that it cannot find any stars - what does this "Detecting stars: done
872 stars found." mean?

Magnus

[pfile]

you need to see how many stars were detected in the reference image. if the reference image is significantly worse than this image, it may not be able to find a common set of stars between the reference and image 3.

it may also have just found hot pixels instead of stars. you can set star alignment to "detected stars" mode and you can then look at the output to see what the objects are that it thinks are stars.

rob

[oldwexi]

As your image is not calibrated or not correct calibrated the hot pixels
are interpreted as stars.

However only with the raw calibrated reference fits image and the raw calibrated fits Image
which does not Register a clear answer can be found.
Cropped stretched JPEG Images cant be used for finding the reasons.
Gerald

[magnusl]

Hi!

Ah, I found it. I had not debayered the images. The sequence I followed used raw images, but I have switched to fits, but missed the debayering step. Now they register nicely. Despite bad focus.

Magnus

[pfile]

cool, glad you found the solution

rob