NavList:

'Evening, Peter.

Probably not related to the horizon shades at all, though I am curious about the 2nd photo. You already mentioned that  you removed the scope,  and, yes I too can see the two suns, but the camera is not looking directly down the normal line of sight, does looking throught the scope show the same displaced sun ?

Another thought, I went back along the anwering posts and can find no mention of checking the perpendicularity, prior to doing the correction for side error and then Index error.   At Trinity House Navigation School, we were taught to refer to the error and their adjustments, as ...'first error=perpendicularity of index mirror'.  '.first adjustment= the correction of the first error' and that was the very protocol expected at any Board of Trade exams on navigation principles.  It was such a very basic ,fundamental  routine and perhaps very much taken for granted by folk who used these instruments.

So,perhaps you have not known of the  full , pre-use routine before, if so,  a basic search on this site will show all that's needed.

Lawrie