A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Art Leung
Date: 2022 May 11, 09:29 -0700
Sorry to come to this conversation a little late.
As previously mentioned, the distortion you see is from a damaged pellicle. I have fixed these with clear plastic wrap and overhead transparancy film. Both work fine - transparancies are easier to work with but the clear plastic wrap makes for a better image.
If the bubble cannot be adjusted down by working the knob while tilting the chamber left, then you can try what I did here:
Refilling a Kollsman Bubble Chamber – a guest post by Arthur Leung | The Nautical Sextant (sextantbook.com)