That is bad seeing! From the top of your mountain I managed to get slightly further south than 62S: https://www.flickr.com/photos/nickdjames/34749184922 . Horizon depression at 2,200 m is about a degree I think.

Tacande's latitude is 28.642N, so at the surface of an airless spherical planet the southern horizon would be at a declination of 61.358S.  My figure of 62S is a convenient approximation which allows for half a degree of refraction and a bit more for an altitude of 765m above sea level.

The major problem at Tacande is that the seeing is ruined by turbulence in katabatic winds coming down from the Cumbre Vieja to the east. They are especially prevalent during a calima where hot Sarahan air (and dust) comes over. On a good night the seeing here is 2 to 3 arcsec, as it was last night.  On a truly bad night it can easily be 15 arcsec!

Those figures are for low airmass / high altitude. Seeing is almost invariably worse closer to the horizon.

One advantage of aperture photometry over imaging is that, within reason, bad seeing is not a show-stopper. Only in crowded fields does it matter (much) that the aperture and annulus needs to be set higher than in conditions of good seeing. Indeed, many photometrists at good sites purposely defocus so that the stars' images are spread over more pixels, thereby averaging out pixel-to-pixel variations in sensitivity. Essentially all my "real" work is photometry and very little is imaging per se.