Image Integration missing keyword error

[cuivenion]

Hi, I'm using this guide:

http://www.lightvortexastronomy.com/tutorial-pre-processing-calibrating-and-stacking-images-in-pixinsight.html#Section5

I'm using image integration to get my final image but I'm getting an error as shown in the attachment. In the next attachment is the fits header clearly shown with the SSWEIGHT keyword that I used. I'm a little confused as to why I'm getting the error.

Any help would be much appreciated.

[cuivenion]

The problem is negative weights on some keywords. I will try adding 75 to this equation instead of 50 at the end.

(10*(1-(FWHM-5.209)/(6.360-5.209)) + 10*(1-(Eccentricity-0.6066)/(0.7352-0.6066)) + 30*(SNRWeight-2.178)/(2.343-2.178))+50

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Adding 100 solved the problem for me.