ACCURACY?

[Pleiades]

Good day Navigators!
I wonder if anyone has any suggestions on the following?
I have been practicing celestial nav for over 60 years now, at sea in pre-GPS days, and later simply to “keep my hand in”. I have 2 sextants, a vintage H. Hughes which I used at sea, and a modern Tamaya with a 7×50 scope.
I use HO 229 and 249, shooting the sun via a water art horizon. I live on the 17th floor, but with the AH I don’t need to correct for dip. I use ephemeris from the Nautical Almanac and refraction from Bennett 1982.
Both sextants have been cleaned up for errors, and both give exactly the same results; my p/ls always run between 0.7′ to 1.2′ to the west of my known position. I have tried using the interpolation tables, table 5, and interpolation by maths, and always end up in the same place. This is based on ~50 sights!
I have picked my known lat/long from Google Earth and that is confirmed by a plot on the Admiralty charts.
I can only get the sun later in the day…when LHA = around 50 – 65….as I am blocked in the mornings. I can’t get stars due to light pollution.

So why the constant error to the west?
Is it finger trouble? (Maybe but also maybe not!)
Is the refraction somehow incorrect due to my h.e. ? (A question mark here?)
Is there anything that needs to be applied due to the h.e.? (Not that I can think of.)
Is there a slant in both tables which, if I could get sights in the a.m. would cancel out the westerly error? (I doubt so.)

I look forward to your comments!
Jon

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