Integration fail on 2sec exposure M42

G

gottsch

Well-known member
Hello All,

I'm trying HDR on M42 with exposures of 2sec, 10sec, 60sec.
The 2sec exposures fail in SatrAlignment. I'm highlighting the error given for a sample image below.

From log:
...
* Previous attempt failed - this is try #19
useScaleDifferences=false
* Reference image: Limiting to 3000 brightest stars.
* Target image: Limiting to 3000 brightest stars.
Matching stars: done
1052 putative star pair matches.
Performing RANSAC: done
* Previous attempt failed - this is try #20
useScaleDifferences=true
* Reference image: Limiting to 3000 brightest stars.
* Target image: Limiting to 3000 brightest stars.
Matching stars:
1008 putative star pair matches.
Performing RANSAC: done
*** Error:
*** Error: Unable to find an initial set of putative star pair matches.
...
===== StarAlignment: 18 succeeded, 12 failed, 0 skipped =====
03:12.03

Yes, there are not so many stars, but a stretched image doesn't look so bad. I am showing the image 0028 which had triggered the error in the log.

M42_2sec_StarAlign.jpg


Thanks,
Gert
 
It is always difficult to help without working with the data, but the problem is typically the large amounts of noise and uncorrected hot pixels. Two parameters should always be used in these cases:

- Minimum structure size. Set it to something in the range from 20 to 40 pixels (just guessing).

- Noise reduction. If the above doesn't suffice, increase the value of this parameter to 2 or 3 pixels (again guessing; you'll have to try with your data).

One or both of the above parameters will surely allow you to register these low-SNR frames without problems.
 
Hello Juan & All,

I found a prev. comment on same error message in the forum archive.

Unable to find an initial set of putative star pair matches

Hi, I am not being successful in performing a Star Alignment with PixInSight. I don't understand why this is so difficult to do with this software, as I have had experience with others that worked very well. I have 25 exposures from a Canon 6D (first, not Mark II). I am using the newest RAW...
pixinsight.com

John Gill recommended:
Star Detection
- Detection scales 3
- Noise scales 0
- Hot pixel removal 1
- Noise reduction 5
- Log sensitivity -1.00
- Peak response 1.0
- Maximum distortion 0.500
- Upper limit 1.00

Star Matching
- RANSAC tolerance 7.00

Following the above the alignment went fine.

Best,
Gert
 
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