Global Star Alignment doesn't find any stars during registration

Hello,

I’m new to Siril, so far I’m not very impressed – quite difficult to use with the latest version.

Anyway, I have several images, all very clearly have stars in them yet Global Star Alignment reports no stars found in the image. I’ve tried playing with Dynamic PSF to no avail – spent over an hour changing the 3 values and not a single star was found. There are several concerns, for example why this should even be necessary, but the concern right now is why this doesn’t work. Is it a but? User error? Both?

Thanks,

Gary

Last official version, or dev version? Both are very different, and the dev one is better for star detection.

Thanks so much for the response.

Latest official version.

/Gary

Maybe changing the reference image will help.
Sometimes Siril fails to find stars (not very often), especially 0.9.12 version. The future version will fix that.

Awesome! I’ll play with it some more.

Thanks,

Gary

Hi,
maybe your stars are too elongated, maybe they are too faint but appear bright because of the rendering, maybe they are overexposed and cannot be detected as a Gaussian shape… Share an image maybe, we can have a look.

Hi Vincent,

I suspect you are on the right tract. They are not very good images, lots of background light.

I’ve played with it a bit more, and will do again today.

I’ve stacked (poorly) a few images using the single star registering and Siril can detect stars in that stacked image (with default settings), but not detect any stars in the original images (even adjusting the parameters).

I’ll send an image shortly.

Thanks,

Gary

Hi Vincent,

I’m having issues with sending the image, it bounces off of my email server. Is there another way to send the image?

I’ve been learning the camera and thought I’d extend into stacking some images — was looking for some SW to make that simple. Images were originally saved by the camera in JPEG format (I know that it is better to save in RAW format and will do so in future tests). Using Siril I converted the JPEG to FITS format and proceeded to learn and experiment with the tool. BTW, I’ve also found that any of the Siril FITS files “re”saved into any other format are blank (all black), so 'SaveAs…’ doesn’t work with these files either (I didn’t try to resave as FITS, but bmp, jpg, tiff, png are all blank).

I think this will come down to a combination of SW bugs, image quality, and user error (it’s odd that stars can be found in the stacked image but not the originals, and as a SW developer that is a great clue as to what’s going wrong — either bug or user error).

Thanks,

Gary

Use the web interface and drag and drop your images onto the editor window.

Your original images from jpeg converted to FITS are probably in 8 bits per channel while the stacked images are in 16, maybe the dynamic is simply not good enough for star detection, or maybe there is a bug with 8-bit images to that regard.

Saving the images has issues with 0.9.12 I think, but in any case, they should be saved in the same way they look when the linear rendering mode is active, so very dark. If you see them with other rendering, like the autostretch, they become much brighter and this is misleading, but it’s explained widely in the documentation, videos, forums.

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You are all amazing, thank you so much.

I’ve included two images, one that doesn’t work and one that does. Vincent was correct, the 8 bit images fail star detection (at least Dynamic PSF doesn’t find any with the 8 bit, but finds many with the 16 bit, using defaults). The failing image is directly converted from jpeg. The working image was resaved as a FIT file 16 bit unsigned.

Thanks,

Gary

notworking.fits (68.7 MB)

working.fits.zip (41.6 MB)

I guess my next question is how to convert all the jpeg images to 16 bit FITS.

Pointing me at manuals and videos is very welcome. :slightly_smiling_face:

Thanks,

Gary

The main issue is that the stars are saturated in the raw image, so they are in the stacked image too. There’s a bit more signal around the saturated pixels in the stacked image so the algorithm is able to find stars, but not in 8 bits.
You cannot convert the JPEG into 16 bits, or not in a meaningful way, because JPEG images are 8 bits.

So next time, shoot in raw, but also try not to burn the images, it’s not a problem if objects appear faint, with stacking you’ll get them.

Thanks Vincent, I’ll do that from now on.

I appreciate everyone’s advice.

Thanks,

Gary