PixInsight error running SPCC on a preview

You likely have a preview region named “Background” selected as your target image.

Note this is different from setting that preview as your background reference — that’s correct. But your target image — the one SPCC is actually operating on — needs to be the full image, not a preview of the full image.

Getting the hang of PixInsight would take a while :)

You are supposed to run SPCC on the whole image.

What quick start guide suggests is to create the preview of stars-only region and drag it to “Region of interest” for background neutralization. The reason is to avoid taking a fairly large object like a galaxy treated as background. (You can do without this step, and just SPCC the image wholesale, yielding an imprecise result.)

But after you dragged the preview to SPCC box, and — accidentally or intentionally — selected the preview tab, you now need to select the whole image tab back, so that SPCC gets applied to it, not to the (currently “active”) preview. Once you select that tab, either press “Square” button to apply to this current image, or drag “Triangle” from SPCC process over the image to tell it explicitly what to work on.

Anthony (Tony) Johnson · Jul 17, 2026, 06:52 PM

In reading through the pages you referenced they are telling you to set the region of interest to your Preview you selected by dragging it to that part of the box and dropping it. It will then set your background to the preview. SPCC will then run on your image but use that part as the background neutralization. You can select it from the from preview button. That will open a select preview box with a drop down that you can then select your preview. Either way works. If you’re not to good with the drag and drop then just use the select preview button. I use SetiAstro’s find my background routine. His repository is on his website at SetiAstro.com. That way you know you actually have the background selected with no nebulosity in it. It needs to be the background and nothing else. I wouldn’t even put stars in it. Why I use his script for finding the background. It’s just easier. I like easy.

Tony - this comment was deleted due to erroneous information given.

CS

Bob

Again did a search;

In PixInsight, here is how you effectively set your ROI:

1. Create a Preview: Draw a preview box over a dark area of your image that contains no stars and no major nebulosity.

2. Configure SPCC: Open the SPCC process window and locate the Background Neutralization section.

3. Select your ROI: Check the Region of Interest box and select the name of the preview box you created (e.g., Preview01) from the dropdown menu.

4. Execute: Run the SPCC process to neutralize the background sky and accurately calibrate your image's colors.

   So this has always been my understanding as to how to use the ROI in the SPCC process.

Anthony (Tony) Johnson · Jul 17, 2026, 07:14 PM

Bob Meincke · Jul 17, 2026 at 07:02 PM

Tony - For SPCC background neutralization, you don’t want to use the Find Background script, that’s for the Neutralize Background Script. SPCC neutralization works differently in that it wants lots of stars in that preview for better color calibration. I just found that out when I was having issues calibrating an image yesterday. So, essentially if your image has lots of stars, no preview is needed. Just check the background neutralization box.

So I did a search; you might note SPCC, and I’ve used it that way since he published it and to my knowledge the reason he came out with it. But as always I could be wrong, but these are not my words.

From the search;

FindBackground from SetiAstro automatically finds a good (or best possible) object-free background region in dense star fields and nebulae, where it is often hard to know which area has no objects. It then shows a preview of the chosen background and prints key values like average background brightness per channel, color correction constants, and the background region coordinates for easier use in workflows such as SPCC or Background Neutralization.

Heres the link to his youtube video that explains how to use the script:

https://youtu.be/qrlH_R4WwmU?si=HIki6nuP-Lh8_zSe

of course there has been updates since that video and he has others explaining it.

Tony, I stand corrected - as said, the way you do it is how I’ve done it until yesterday. here’s an update from my source. “Correction: I previously said that SPCC’s Background Neutralization should use a starry preview rather than the star-free preview created by FindBackground. That was incorrect.

SPCC does not need stars in its background reference. The reference should represent true background sky, with as little stellar signal, nebulosity, dust, or gradient contamination as possible. FindBackground is specifically designed to locate such a region and create a suitable preview, so it can work very well with SPCC. The important step is still to inspect the selected area, especially in fields filled with faint nebulosity where genuinely empty sky may not exist.” so with that said, my sincerest apologies for passing along bogus information. My source is ChatGPT when I was having an issue getting my image to color calibrate, showed the settings I had set that were wrong and we modified some. That’s when it told me what I said today. I will modify my response so others do not go down my FUBAR rabbit hole. Thanks for correcting me.

Bob