ISS Lunar transit processing

[Peco4321]

I was lucky enough to capture an ISS transit of the moon the other night but need some tips on processing please.  I captured .ser, about 5100 frames, only 90 of them are the actual transit.  What I have done so far is using PIPP is extract those 90 frames into tiffs, using an old version of GIMP, I have produced and image to show every frame of the ISS passing though it is not very sharp. For lunar my normal workflow is Autostakkert and Registax to produce a final sharp image, but stacking in AS takes out all the ISS as I guess it is seen as an anomaly, the purpose of stacking!  I can't get as good an image if i try and process the tiff made from the 90 in GIMP, it just does not achieve anything loading it Registax and messing with it, as it is a non stacked image.

Any thoughts what I can do, can I stack and keep the ISS on the final stacked image somehow.  Here is the image produced in GIMP of the transit, and an image from AS and Registax that I would like to have the transit on, saved as Jpgs to upload quicker, but they are tiffs.

[Clavius D]

Beautiful picture. Well done