Plate Solving failed with Photometric Colour Calibration

Hi Team,

This error is quite common for me when trying to color correct my stacked Fit files. I usually try a bunch of stars or nebulae or anything that’s related to the image, But itseems to fail most of the time. Anyone got any suggestions to fix this.

I am shooting with a Fujifilm X-T4, and this image below was shot with a 18-55mm f2.8.

I see you are trying to do it on a wide field. Wider the image is, more difficult the plate solving will be.

I thought that too but I’ve had the same issue with images I’ve taken of single objects. Any suggestions to solve this? I’ve tried Astro Pixe Processor and it resolves any image automatically

Doing astrometry for just astrometry is not the same that doing astrometry for photometry.
We don’t use same catalogue. The one we are using has less stars.

And probably our astrometry tool would work.

All I want to do is colour calibrate the image above dude. If possible, Clear instructions would be appreciated

I think your field is too wide.

  • You can try other image center (like a star that is really in the center).
  • You can try astrometry within Siril, with the other plate solving tool.
  • You can try to make astrometry with another program that save it in FITS keywords and use the result in Siril.

But photometry will not be optimal when I see your vignetting. Don’t expect something good. Photometry must be applied on flat image.

Then, Siril has another color calibration tool just in case.

What is too wide for Siril’s Photometric color calibration to fail to plate solve? I have images from a 35mm lens and 105mm lens that Siril fails to plate solve. Yet with the images can be plate solved. I’ve tried using the maunal color calibration, but the colors are off. I would really like to see Siril plate solve wide field images. I could understand maybe that an image from the 35mm might be too wide to plate solve, but I would hope it would be able to work with a 105mm lens. Below is the image from a 105mm lens I was hoping to plate solve with Siril.
Any help is apprecaited.
Won’t plate solve in Siril, but will with nova.astrometry

You have to understand that is tailored for astrometry. Not siril. Siril uses astrometry as a tool. is much more powerful but you can use the result of this later to try to perform the photometric color calibration with Siril.

OK, that’s understandable, I wasn’t trying to insult anyone, I’m very impressed with Siril.

Can you please explain how to enter the results from into Siril to perform the Photometric color calibration? I see there is a check box to enter stars manually but I don’t know how to select one or enter the data.

Thanks for any and all help,


You just need to get the image center given by the astrometry, and to report it in Siril (with the right focale length and pixel pitch)

OK, thanks, I have the center RA and Dec from It also reports the radius and as 12.061 deg and the pixel scale as 30 arcsec/pixel. How do I translate that to the focal distance, Pixel size, and resolution I need to enter in Siril. My camera has 5.97 pixel pitch ( its a D750) and I was using a 105mm macro lens. When I use the meta data from image in Siril , it reads the correct local length of the lens and the pixel size and calculates the resolution. Does cropping the image after stacking make the meta data values incorrect? Do I just alter the focal distance till the Resolution values equals the Pixel Scale reported in I tried that and used 41mm as the focal length left Pixel size = 5.97 and the Resolution was 30.034, nearly the value reported from nova, and Siril could still not plate solve the image. Any ideas? Attached are the results for astrometry.

So like it does not work, use the other color calibration tool.
It gives good result too…

Thanks, you probably should not make suggestions for work arounds unless you really know they will work. Getting the values from astrometry would not have been too big of a deal, but it didn’t work at all. The colors look off using the other color calibration tool and the the histogram tool doesn’t appear to be able to adjust just one channel at a time. At least I haven’t figured out how to adjust just one channel. It would be nice if the Photometric Color calibration worked with wide field image.

Same here. Aps-c nikon and 35mm lens and whatever focal length, stars, or pixel size I put there, it can’t plate solve in 99% of the case. This worked better with 0.99.7, not always but increasing focal length it got to plate solve the image. now I tried from 35mm up to 60 in 1mm increases and it didn’t. Thanks for the suggestions, will try that.

Edit: plate solved with astrometry and copied the RA and Dec central values into the right fields of RA and dec and now it did plate resolve. That worked!

Edit2: What I don’t understand is why the RA and dec are way off from a star in the center of the image that I searched for in the image parameters field and the central RA and DEC which nova.astrometry provided. I mean, star 35 ERI is in the middle of the image, and it shows RA: 32.0446 and DEC: 58.7112 and astrometry provided RA: 59.732, DEC: -1.886
This is the image:

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Well, this works with some cases. What seems to work quite good is the following. Determine center RA and DEC via paste that values into the photometric color tool. select a star in the image, right click, select “pick a star”. Up the threshold to something like 1.20. do a star detection with the first button below. Go back to the photometric color tool and enable manual star detection. Do a manual background reference selection, too. It seems to help with light polluted images. Of course, if it doesn’t help either, play with these values. At least it helped for me.

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Hi, you may see on the image that the annotated positions are not quite on the stars, it’s probably because of geometric distortion of the lens system.
I think the method you are suggesting is in fact the recommended method.
It’s not easy for siril either to work on noisy and distorted images for a plate-solving that is not as powerful as the one from

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That worked for me thanks very much @nightspace

Now with the last version this isn’t necessary anymore, just enter a star that is in the centre of the image and it will normally solve it correctly.

En 16 feb. 2022, en 14:45, “ozguru via” <> escribió: