Image analysis software to quantify vignetting

[Max N]

I'm using a Celestron Edge HD 8" with full-frame sensor. There is some vignetting, and I have recently realised a lot of this is not due to the scope itself, but is caused by the adapters between the visual back and the camera. I've taken a series of flats with various adapters, and I'd like to quantify the differences between the different setups so I can recommend to other users of this scope what the best setup is. I can't afford CCD Inspector (and I can't justify the cost for this simple task - maybe in the future). Is there another piece of software (or method) which will analyse the images and allow me to quantify and compare the vignetting objectively?

Or if I post the images, can someone analyse them and post the results? If so, what's the best format to post the images?

Cheers

Max

[Oddsocks]

ImageJ is probably the best of the free image analysis applications for a scientific approach, it is quite a learning curve though.

https://imagej.net/Welcome

Alternatively, fiji is an enhanced version of ImageJ

https://fiji.sc

Both imageJ and fiji are applications written for microscopy but can be used for astronomy image analysis.

Another alternative is the free ESA/ESO/NASA Fits liberator, very simple to use, you can measure, scale and stretch astronomy images, read pixel values and save tiffs.

https://www.spacetelescope.org/projects/fits_liberator/download_v30/

If you want CCD Inspector analysis by interested parties you would need to supply images in fits format, 32bit or 16bit or uncompressed or 16bit tiff in a shared Dropbox or Google drive as jpegs posted here on the forum are downscaled in bit depth.

There used to be a free evaluation period for CCD Inspector, I'm not sure if that still applies.

PixInsight can also be used to evaluate flats in a scientific manner, again, there was a free evaluation period available, you would need to check on the website to see if that is still the case.

[vlaiv]

+1 for ImageJ

You will be able to make something like this:

Which I suspect will be enough to quantify vignetting.