NavList:

The idea the effect of tides on dip seems very academic to me.  A change of a few feet or perhaps a meter at a distance of 10 nm seems inconsequential to the similar effects sea state would have on both the ship and the apparent horizon.  If there is a seaway, the height of eye due to heave, roll, and pitch can change dramatically and easily vary the dip quite a bit, certainly more than a tidal difference in most places in the world. 

 

Also, I would think that given seas of several meters, you get a very different apparent horizon than if the seas are fairly calm.  I was actually contemplating this during my last trip out to sea last week as we were in a gale.  While there were no bodies to observe due to cloud cover, the visibility was about 18 miles and the horizon, while clear, was very different than in calmer seas due to the waves and swell at the horizon.  I cannot give observations to see if this gave me any unusual errors however, but will attempt to do so in  the future.

 

Jeremy