Author Topic: Eccentricity = 0 in Subframe Selector  (Read 593 times)


Offline pfile

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Re: Eccentricity = 0 in Subframe Selector
« Reply #16 on: 2019 October 20 14:56:05 »
that's something else then - your screenshot is of the SFS process, not the script.

anyway clearly something is wrong here - juan would have to take a look - i know that the new StarAlignment module does all sorts of stuff with PSF fitting so it could be that both the SFS script and SFS module need updates to take this into account.

rob

Offline smccully

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Re: Eccentricity = 0 in Subframe Selector
« Reply #17 on: 2019 October 20 15:03:27 »
Yeah, this was always working and then even prior to the recent 1.8 update it stopped working. So i am not sure its actually related to the rework, though i really dont know

Offline dkuchta5

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Re: Eccentricity = 0 in Subframe Selector
« Reply #18 on: 2019 October 20 18:19:47 »
smccully: Good to know.  I checked a friend's installation on Windows and he was getting good eccentricity numbers, and it works for me on my Windows laptop.  So I figured it was just a Mac issue.  Not so, I guess.  I wonder if it has something to do with the individual computer configuration. 

-Dan

Offline smccully

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Re: Eccentricity = 0 in Subframe Selector
« Reply #19 on: 2019 October 20 21:07:53 »
I dont know, this was working. No idea what if anything really changed when it stopped working. But it hasn't worked since, even after reinstallation for latest version

Offline Geoff

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Re: Eccentricity = 0 in Subframe Selector
« Reply #20 on: 2019 October 21 02:38:34 »
It’s not only eccentricity that is a problem.  An FWHM less than one arc second is not believable unless you are imaging somewhere in the high Andes.
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Offline Juan Conejero

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Re: Eccentricity = 0 in Subframe Selector
« Reply #21 on: 2019 October 21 06:20:41 »
Quote
It’s not only eccentricity that is a problem.  An FWHM less than one arc second is not believable unless you are imaging somewhere in the high Andes.

I have just measured the two frames linked above with SubframeSelector, and the FWHM values reported are 3.3 and 3.6 arc seconds, respectively for the 25_c and the 29_c frames. I have used a frame scale value of 0.4"/px and a circular Gaussian PSF, just as shown on the screenshot. These FWHM values are quite correct IMO.

It is true that eccentricities are being reported as zero for both frames; I'll investigate this later. As for FWHM, something looks wrong with the measurements being shown here. Can you please upload this entire set of M33 frames?
Juan Conejero
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Offline dkuchta5

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Re: Eccentricity = 0 in Subframe Selector
« Reply #22 on: 2019 October 21 06:47:59 »
>> I dont know, this was working. No idea what if anything really changed when it stopped
>> working. But it hasn't worked since, even after reinstallation for latest version.

My experience exactly.  Installing the latest version did not change the behavior.
-Dan

Offline smccully

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Re: Eccentricity = 0 in Subframe Selector
« Reply #23 on: 2019 October 21 12:15:56 »
Quote
It’s not only eccentricity that is a problem.  An FWHM less than one arc second is not believable unless you are imaging somewhere in the high Andes.

I have just measured the two frames linked above with SubframeSelector, and the FWHM values reported are 3.3 and 3.6 arc seconds, respectively for the 25_c and the 29_c frames. I have used a frame scale value of 0.4"/px and a circular Gaussian PSF, just as shown on the screenshot. These FWHM values are quite correct IMO.

It is true that eccentricities are being reported as zero for both frames; I'll investigate this later. As for FWHM, something looks wrong with the measurements being shown here. Can you please upload this entire set of M33 frames?

https://www.dropbox.com/sh/n6rp6090dq7k67k/AAADSR7IZI0fkdAth-ASM9aea?dl=0

Offline Juan Conejero

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Re: Eccentricity = 0 in Subframe Selector
« Reply #24 on: 2019 October 22 08:10:42 »
Thank you for uploading the images. I have no problem at all to measure them with the current version of the SubframeSelector tool.

If you force measurements of circular PSFs, then eccentricity has to be zero. Eccentricity is defined as:

sqrt( 1 - (sy/sx)2 )

where sy and sx are the standard deviations of the fitted PSF function on the vertical and horizontal axes, respectively, and sx >= sy conventionally. In the circular case we have sx = sy, so eccentricity is equal to sqrt( 0 ) = 0. So this is the expected behavior.
Juan Conejero
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Offline Juan Conejero

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Re: Eccentricity = 0 in Subframe Selector
« Reply #25 on: 2019 October 22 08:27:54 »
See the enabled Circular PSF parameter in your screenshot.
Juan Conejero
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Offline dkuchta5

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Re: Eccentricity = 0 in Subframe Selector
« Reply #26 on: 2019 October 22 17:12:11 »
And we have a winner!   Thank you, Juan !!!

I checked in the Script under the Star Detection and Fitting panel and sure enough, the circular PSF was checked. I have no memory of changing that.  In fact I never change anything in that panel.  I wonder if the default got changed in some release?

Anyway, it works now.  Thanks again!

-Dan

Offline Juan Conejero

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Re: Eccentricity = 0 in Subframe Selector
« Reply #27 on: 2019 October 23 03:10:20 »
Quote
And we have a winner!   Thank you, Juan !!!

Now you owe me a virtual beer! ;)
Juan Conejero
PixInsight Development Team
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