Bug 460040

Summary: Variable HFR values
Product: [Applications] kstars Reporter: Jean-Claude <jcjesior>
Component: generalAssignee: Jasem Mutlaq <mutlaqja>
Status: REPORTED ---    
Severity: normal    
Priority: NOR    
Version First Reported In: 3.6.1   
Target Milestone: ---   
Platform: Other   
OS: Other   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:
Attachments: HFR = 3.93
Variable HFR values

Description Jean-Claude 2022-10-06 09:47:04 UTC
Created attachment 152612 [details]
HFR = 3.93

SUMMARY
During a session , recorded images are displayed in the FITS Viewer with their HFR value.
But if the SAME image is read immediately after in the FITS Viewer its HFR value is different .
Why ?


STEPS TO REPRODUCE
1. Record an image and note its HFR
2. Open the same image 
3. It has now a different HFR

OBSERVED RESULT


EXPECTED RESULT


SOFTWARE/OS VERSIONS
Windows: 
macOS: 11.7.6
Linux/KDE Plasma: 
(available in About System)
KDE Plasma Version: 
KDE Frameworks Version: 
Qt Version: 

ADDITIONAL INFORMATION
Comment 1 Jean-Claude 2022-10-28 08:16:48 UTC
Created attachment 153253 [details]
Variable HFR values
Comment 2 Jasem Mutlaq 2022-10-30 06:02:08 UTC
I believe this is because different algorithms are used to measure. Some only examine a small area in the image to measure HFR, others measure HFR in all the stars and take an average.
Comment 3 Jean-Claude 2022-10-30 06:55:01 UTC
Your explanation could be valid : in my attachment, the "Just recorded image" uses 1747 stars while the "Same image read from disk" uses only 244 stars.
But why not using the SAME algorithm ? This is confusing !
Comment 4 Jasem Mutlaq 2022-10-30 07:06:31 UTC
Good question, it comes down to performance issues. This might not matter on very fast computers, but it makes a big different on limited hardware.