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    Celestial suggestions
    From: Rick Emerson
    Date: 1998 Aug 24, 11:23 AM

    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
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