Add Eccentricity Measure to Image History and Image Grading

I love the image history. In fact one of my earlier requests resulted in
it. I find it very useful. But currently there is no measure of
eccentricity either in the image history or in image grading.
Unfortunately it is quite possible to have a sub that looks great from a
HFR point of view that is horrid from an eccentricity point of view. My
preference would be that eccentricity be added to both image history as
an option and to image grading. But if I had to have it just one place
or the other, I would choose to add it to image grading.

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I like this idea. I too sometimes get a low HFR image that has elongated stars, and a tool to measure it live would be really helpful.

I agree. Eccentricity is really useful. There is a good thread on the PI forums about it.

I would like to add my vote for this as well.


I’m unsure if the math to calculate eccentricity is appropriate for whole-image measurements. Is anyone else doing this? Moving to archive for now… (not because I think it’s a bad idea).

Was thinking of requesting this, but found this archived feature request. Not sure how PI calculates eccentricity for the whole-image (I think CCDInspector also calculates this as Aspect). Yes, I have PI and could use the SubframeSelector script, but like all things PI ease of use isn’t the first priority. In PI it’s a multistep process to run the script, then you have to close the script before you can open Blink to view and compare the images visually. Nice thing about adding this feature to SGP is that it would make it a simple and easy to use solution. HFR gives you a measure of star bloat, # Stars give you a measure of sky background and contrast. Add eccenticity and it would be a complete solution to sort images and quickly bring them up on the screen for viewing. Sometimes the simplest interface is the best.

Ya… I’ve always liked the idea of doing this. The new AF moved in the right direction for flexibility and resilience, but in the wrong direction for speed (computational intensity). It is probably worth a try to see what kind of penalty is incurred.

Out of curiosity, besides general information and usefulness when grading the quality of an image, are there any other aspects of automation to which this metric might apply?

As the OP said in the first post, it would also be useful for on the fly assessment in Image History.

I wonder why eccentricity was never added to image history and image statistics. Would be a very helpful feature for image and equipmet setup evaluation

The SubframeSelector tool in Pixinsight calculates a large number of image metrics in its image analysis, including FHWM, eccentricity, SNR, etc. It consumes significant processing resources.

SGP already consumes between 25 and 40% CPU time when running a sequence. When imaging in the field, this causes more drain on batteries. Increasing processing demands on the laptop will have an adverse impact. To upgrade to larger capacity batteries with new battery boxes etc. would be costly and add more weight to lug around. Recently, the software engineers developing Celestron’s CPWI mount control package made a significant effort to reduce CPWI’s CPU consumption. They lowered it from about 25+% to between 6 and 8%.

If SGP were to add additional computations, I would advocate for them to be in image grading and not image history. Also, it would be very useful for SGP V4 to reduce CPU consumption if possible.

Mark W

I think PC power cosumption has more to do with hardware efficency than with SGP. Of course software plays a role also, but if you just run SGP you will not see a big difference in power consuption when SGP is running. I am running a mobile rig with a dedicated imaging mini PC, a Zotac PI 335 that just consums an average of 12W (I continuously measure voltage, current and power being drained from my battery with an accesory I truly recomend you to install if you are a mobile imager). I connect my laptop to the Zotac with a lan cable and Microsoft Remote Desktop to configure and start the imaging session. When all is set up I disconnect my laptop and leave the Zotac running alone. If I want to check somenthing I connect again in less than 5 seconds always through MRD. The Zotac uses way less power that my laptop!
This little extra eccentricity computation would make no difference and on the contrary would help to find some tracking issues (I do unguided imaging).

Martin Seb

PD: The Zotac is even able to run from a normal 5V phone powerbank!
Of course I would NOT like to run PI on my Zotac just to measure eccentricity…

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