NavList:

Took a C & P  sextant today in the balmy december weather, and used Frank's technique (as  understand it) to up set the horizon mirror and set index correction. I used my stanley london 20x spyglass, a beautiful gift from a lovely lady now passed.

I can only say the ease and results were spectacular. I used a far distant vertical flagpole in view of my boat dock, wth the sextant standing on its legs.  I had previously set this mirror for a .1 - .2 index correction using the sun SD method and distant roof edge checks. With the scope technique, I was able to literally zero this one out from this preliminary setup.  Later sextant checks with its own scope remounted proved out the initial happy results. 

Can't wait to try it on my own Astra III and especially my old davis plastic.  THe plastic makes me totally waka waka because index vs precision error can be hard to evalaute at times. I find a tight hand grip on my Davis can distort the readings.

PS I also find using a high grade low friction lube on plastic sextants to be key...as it reduces tiny little sticking errors and incremental jumps.