3x3 Mosaic Aberration Inspector

Would like to have a simple 3x3 mosaic aberration inspector to check all cornes of the frame.
Scrolling to each corner of a FF chip has become a very demanding task :sweat:

I KNOW there are other softwares that can do that, BUT opening a file in another software just to see an overview of all edges is even more time consuming, therefore doing it directly in SGP would be a hit.

This would be a nice addition that won’t hurt, and DO NOT tell me that noboby scrolls to the edges at least a few times per night!!



I’m not sure what you are asking. You are displaying your frames at 100% zoom and then looking at the edges of your frames to check the quality of the star images?


Correct Charlie, at 100% or more depending on screen size.
With my former 1600 sensor scrolling was ok, but now with a FF sensor, it takes way more effort to scroll to each edge. I am not lazy, just trying to optimize muy imaging time with a new small usefull function.

Here is an example taken from PI


I don’t have the patients to do a mosaic so I am not familiar with the PI mosaic function. I am not sure that viewing the frame edges in SGPro is going to do you any good as SGPro can’t do anything about the star quality in your frames.

What changes would you make to your imaging run in SGPro, if you had this function?

Perhaps telling SGPro to have a larger overlap and then using the Crop function in PI to remove the overlap would help get rid of poor stars in the corners. You can only remove the overlap; otherwise, I don’t think the frames will stitch together correctly.


SGP can’t do anything to correct my star quality in the cornes but I can do something in the imaging train if I see the problem before waisting precious time.

Anyway, unfortunatly I don’t think the culture of SGP is about adding new functions, just polishing the existing.

I would be more than happy to have aberration analysis tools in SGP, e.g. inspector (as in PI) or tilt analysis (as in ASTAP).

Hope, this comes on one day.

yeap, some kind of basic image analysis in addition to the standard HFR and star count, would be very appreciated, at least the here-mentioned aberration inspector and an eccentricity measurement. I am constantly switching between SGP and CCDInspector. Basic image analysis is fundamental to avoid wasting precious imaging time.

I am switching between SGP and ASTAP. Even a simple “single-button solution” (I suggested this some time ago) which throws the image into ASTAP or CCDinspector without the need to save manually it into a folder, would be a huge help for collimation sessions.

Well, collimation is another thing.
It’s a useful function, but I don’t think it necessarily needs to be integrated into imaging software. Imaging is one “complex” process and collimation is another “complex” process. Of course, evaluation of an image is also another process, but basic evaluation as is HRF and star count could be complemented with another basic value, as is eccentricity and a time-saving 3x3 aberration inspection window instead of manually zooming and scrolling to each of the 4 corners of the image

Count me as a vote for this feature request. Sure would be nice to get some more image inspection features as mentioned above.

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We do actively add new features to SGPro. We also polish existing ones… Trying to do both of these things while providing support is difficult and time consuming so it’s understandable to think we don’t add new features I suppose. It’s just slower… we don’t have the manpower.

Anyhow… new stuff:

As for stuff like this, we do read through, collect and prioritize (usually based on popularity… but sometimes other stuff)

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Also… we do calculate eccentricity currently, but it has never been tested or used in any way. If you have a “eccentric” data available, please send it our way and we’ll work to expose it.

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Alright… just a check in here. I did some work to expose this metric. The goal, in the is case, is to see if we can provide something useful in a pretty quick way so that it doesn’t compete with AutoFlats and Custom Horizons (SGPro 4.3). Assuming this is somewhat useful, it can also go into 4.3, but before we talk about that, let’s review the state of things.

In order to get an accurate measure of eccentricity, I was forced to re-evaluate the way in which we find and measure star fields. The current method in SGPro uses a method that is a compromise between accuracy and speed. It really just deals with centroid calculations by bounding the star in a rectangle and then finding the centroid in said rectangle by calculating the center of gravity as dictated by pixel intensity. All said, it’s fairly accurate and reasonably fast. BUT… this method does not produce accurate measurements for star eccentricity. The work I have completed recently refactors this method a good deal and uses proper ellipse detection through a least squares fit. Much to my surprise I was able to tune this method such that the find stars method only incurs an additional time penalty of 1 ms per star on the image (usually around 1/3 of a sec for most images). I think this means that eccentricity can always be measured, but SGPro will still provide an option to disable it… the reason being that SGPro is already a wall of data and stats. If you don’t use or need eccentricity, you don’t need to have it add to the clutter.

So now we have access to eccentricity, but how does it become useful in a way that does not require weeks of work. This is my proposal, but I want to see if it meets needs regarding the subject of this thread, if it falls short and if there are any quick adjustments that would close the gap between those 2 things.

An in-depth look at this is here:

Specific to this thread, and as an example, from the “bad data” zip file you provided us.


Eccentricity: 0.5
Aspect Ratio: 20%

This doesn’t really mean anything though… What I am hoping you might provide is a sample of a few images from the same events (filters, gains, etc) that you have classified as “good”. In my mind, the absolute number isn’t the most important aspect of this measurement, but rather that there is an actual difference in the measurements between good and bad.

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I am really glad you are moving forward with the eccentricity and a new HFR calculation. You are doing an excellent work with the elaborated approach you are taking. Although you minimize it and do not consider it useful for every scenario, I think this is one (and hopefully more to come) great step forward for SGP and you will see that it was worth it.

I personally don’t mind about time penalty if this adds useful information. Anyway your flexible solution allows everyone to decide if and how to use this new function.

Few questions:

  1. Does SGP need to finish the HFR/e calculation to start the next exposure?
  2. How will this calculation react to very elongated stars? Above certain elongation e will always be 1?


  1. Please do not forget to add the e value to the image history diagram
  2. BTW now that you are inspired, adding mean (or meadian) background pixel value to the history diagram would also be nice cause it is an indication for clouds/haze (sometimes star count is not affected by few thin clouds)…it also allows to see how frame quality is affected by sky glow at lower altitudes, specific sky areas or to early/late imaging start/finish time…
  3. Here is a link with good (and some bad) data from the same (or very similar) events.
  4. In that link there is an excel spreadsheet I made to compare CCDI “ar” and PI “e” values. You can use it to add the SGP values and see how they compare.
  5. Please let me know if there is something else I can help for this (or other) subject.

Not to imply that I am minimizing your desire for it or the workflow you use. I think that the eccentricity measurement may actually make a big difference when attempting to use Auto Focus in star-poor regions.

Sometimes, but most of the time, no. More specifically, SGPro’s current implementation will allow the next frame to start and analyze the last image in the background. If the sequence requires the results of that analysis in order to make a decision about what to do next, then the next frame will wait. Currently, the only case where image analysis does not happen in the background is for the HFR Auto Focus trigger. If this question is more geared toward the notion that high precision measurement can negatively impact time available for gathering lights data, it is Auto Focus that will present itself as the primary offender (and not the image history analysis of sequence images).

I have this noted, but, in all likelihood will be pushed to SGPro 4.4. Adding a new series to image history will take some time. I don’t disagree with the notion tho… the relative measure of eccentricity is likely the most useful user input.

Also a good idea, but I am at least slightly concerned about the potential loss of usability with 4 series on the same small graph. Would probably be ok on the larger graph, but I’d need to think about it for a minute.

I think that, ideally, you would be able to (optionally) plot any of the values in Image Stats over time.

Thanks! The bulk of the changes are complete, but things still need to be tuned and this will help.