NavList:

   

Reply

Paul Hirose writes:
 > One good exercise is to work a sight on a blank sheet of paper, i.e.,
 > don't use a printed form.  I do that on all the Silicon Sea problems.
 > Helps keep me sharp.

I'm not so sure I see it the same way.  The point behind the form is
to be sure the information is complete and accurate.  The layout can
vary with whatever style fits and certainly doesn't need to be
pre-printed (heck, my laser printer doesn't fit on the nav station
anyway [grin]) but a regular and ordered form is important.

I work with a Celesticomp and I lay out the day's information from the
calculator's SSET function (Date, AP for LAN, predicted sunrise and
set, AM and PM twilights, AM and PM best star times, and LHA of Aries
for AM and PM stars) at the top of the day's notes.

Each round of sights is headed with the body (I use the appropriate
symbol, e.g., circle with a dot in the middle for the sun and a line
underneath for a lower limb shot, line above for upper limb), fix
time, He, Ie (checked again after a long round of noon sights),
current *true* course and speed, and fix AP (filled in during
reduction).  If I'm using a stopwatch to time shots, I write the hack
time (the exact hour and minute the watch was started) and then the
stopwatch time for the shot, Hs and, after the round, Hc, intercept
distance, and azimuth (again, this is driven by using a Celesticomp).

A note about times: with the advent of digital watches, it's easy
enough to carry GMT on the navigation timepiece so I do all of my work
in GMT instead of constantly converting back and forth between local
and GMT times.  Where local and GMT times appear in notes, GMT times
are marked "Z": 23:56:34Z.  In cases where times are not on the same
GMT day (for example, the prime time for evening stars is at 0103Z) I
write 0103Z+1 to indicate the time is on the next date.

Anyway, using a consistant form for all work helps when it's been a
long day and the brain's not firing on all cylinders.  Plugging into a
fixed form makes at least some errors easier to spot than might happen
when relying strictly on memory.

 > Oh, you're saying you want to work less, not more!  Well, try this
 > trick.  Since your index correction and dip are normally constant from
 > day to day, you can treat them as a single correction and save
 > yourself some math on the reduction form.  E.g., on Silicon Sea IC =
 > -2.0 and D = -2.8.  So the combined correction would be -4.8.

Er, I'm sorry but I disagree here, too.  For me dip changes because
sometimes I shoot from the cockpit and sometimes from the cabin house
- it depends where the target is and the boat's heading to say nothing
of the boat's motions (kinda tough to head forward with the sextant in
one hand and a notepad and stop watch in the other and still have a
free hand to hang on when the boat's doing a nasty pitch and roll).  A
long session in the sun or a bump on the sextant can shift index
error.  Assuming the index error is unchanged could be a problem.

 > Some sextants let you adjust the micrometer scale to zero out any
 > index error.  I've never handled one of these, but I wonder if the
 > adjustment range is large enough to compensate for dip as well.  That
 > would be great - refraction would be the only remaining correction.

See above regarding shifting dips.

Rick
S/V One With The Wind, Baba 35
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=--=-=
=-=  TO UNSUBSCRIBE, send this message to majordomo@roninhouse.com:     =-=
=-=       navigation                                         =-=
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=--=-=

   

Reply