NavList:

I was lucky enough to be flying on the Solstice, and doubly lucky to have a good leg to try some Sun lines. The only draw back was the huge jetstream Thursday, so we were battling continuous turbulence. Tried to get three sights 5 minutes apart for the traditional groundspeed plot. Turbulence was such, coupled with the oblique angle of the LOP's, that the results were not particularly accurate or useful this time; but still good fun on a special day.  hs' ranged from 9°10' to 8°30'. Declination for all three sights was S26°26.1', dead bottom on the Solstice per the Air Almanac.  Attached is the plot for your enjoyment.  Tracy

Well done Tracy.  It’s lovely to see someone still using celestial in an aircraft.  Which sextant were you using?  Was it in a mounting, or was it hand held?  Did it have an averager, and was it a mean or a median type.  An automatic mean averager should be best for turbulence.  Having GPS to compare your results to is a mixed blessing.  You can assess your results easily, but it can make you realise the limitations of celestial in a high speed aircraft.  We never had anything as good as GPS to compare our results to, so mid-ocean our results might well have been of the same order of accuracy as yours.  I’m attaching the acceleration errors for an aircraft flying at 480kts in the tropopause, the TAS acceleration values being roughly twice those recorded from the pilot’s ASI (para 3b refers), so others can see what you had to contend with.  DaveP