NavList:

Robert Eno wrote:
"I will likely be crucified  for saying so, but I find that a little side
error is a good thing for  determining IC using a dim star. It is much easier
to judge when the two  images are side by side rather than superimposed."

There is no  crucifixion in your future. Quite a few people on the list have
agreed that side  error is not a problem so long as it's not too big. The only
case, in fact,  where it leads to a significant error is when you do
limb-limb index error  measurements with the Sun. Otherwise index "error" is a bit of
a  misnomer.

For sights, I have been happiest recently getting index  correction from a
nearly full moon in early twilight. The edge definition is  excellent. There's
no additional shade error involved and no eye strain from the  glare of the Sun
around the line of sight to the Sun. For the next week or so  there are good
morning twilight opportunities to try this. It's somewhat  important to align
the Moon pole-to-pole when doing this though if you're near  Full Moon, a
little tilt won't do much harm.

There is also a table top  method for measuring index error. I'll stick that
in another  post...

-FER
42.0N 87.7W, or 41.4N  72.1W.
www.HistoricalAtlas.com/lunars 


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