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Re: Silicon Sea: Leg 84
From: Paul Hirose
Date: 2002 Oct 10, 22:51 -0700
From: Paul Hirose
Date: 2002 Oct 10, 22:51 -0700
> We spend 5 days at Hilo(19d 50.0'N 155d 01.0'W) then depart. We get a
> departure FIX at 02:27:00Hrs after sunrise on the morning of 21/07/2002.
>
> 1) What is the Zone Time(ZT) of the departure FIX?
I couldn't figure out the input data behind this question. A later
explanation, directed to someone else, cleared it up. But the scenario
seemed so weird, I elected to disregard the problem. If it had been me
taking departure, UT and position would have been recorded.
2. Total distance from Hilo Departure Point to Hanalei Bay is 296
miles.
3. At 9.3 knots, it will take 31.9 hours to cover the distance.
4. The Sun lower limb is only 10 minutes from the zenith at the noon
sight. It would be difficult to secure an accurate observation, so the
sight should be disregarded.
> 05:30:02 Moon LL
23 20.5 Hs
-2.5 IC
108 36.9 GHA -2.9 D
-156 36.9 A lon N21 00 A lat 65.8 R, SD, PA
-------- -------
312 LHA S24 49.5 dec 24 20.9 Ho
25 08.7 tab Hc 132 Z -38.7 d
-24.8 d corr
-7.2 d corr
--------
24 36.7 Hc
24 20.9 Ho
--------
15.8 away
> 05:34:11 Vega
41 39.7 Hs
104 05.2 GHA N38 47.2 dec -2.5 IC
-157 05.2 A lon N21 00 A lat -2.9 D
-------- -1.1 R
307 LHA -------
41 33.2 Ho
41 33.5 tab Hc N056E Z +5.6 d
0.0 d corr
4.4 d corr
--------
41 37.9 Hc
41 33.2 Ho
--------
4.7 away
> 05:40:00 Altair
21 57.8 Hs
87 04.6 GHA N08 52.5 dec -2.5 IC
-157 04.6 A lon N21 00 A lat -2.9 D
-------- -2.4 R
290 LHA -------
21 50.0 Ho
21 28.4 tab Hc N088E Z 19.8 d
8.8 d corr
8.6 d corr
--------
21 45.8 Hc
21 50.0 Ho
--------
4.2 toward
> 05:43:55 Polaris
20 25.1 Hs
347 18.8 GHA N89 16.1 dec -2.5 IC
-157 18.8 A lon N21 00 A lat -2.9 D
-------- -2.6 R
190 LHA -------
20 17.1 Ho
20 00.9 tab Hc N000E Z 59.1 d
13.4 d corr
2.5 d corr
--------
20 16.8 Hc
20 17.1 Ho
--------
.3 toward
> 05:46:20 Regulus
16 08.0 Hs
234 16.5 GHA N11 57.5 dec -2.5 IC
-157 16.5 A lon N21 00 A lat -2.9 D
-------- -3.3 R
77 LHA -------
15 59.3 Ho
15 56.0 tab Hc N 83W Z 19.4 d
9.6 d corr
9.0 d corr
--------
16 14.6 Hc
15 59.3 Ho
--------
15.3 away
5. Time to use for the fix isn't stated, so I will make it 0530Z
(evening of July 21 local time). My Vega LOP doesn't look too good (I
reversed the sign of d extracted from HO 229), but the others agree at
21 00 N 157 00 W.
6. From the fix position, Pailolo Channel entrance bears 100 true or
090 by the compass. It's only 5 miles away so there's no reason to
attempt a highly refined answer.
7. We should be there in about 30 minutes.
I did all plotting on a single piece of typing paper at a scale of 2
miles per millimeter. To do as well as I did at that scale requires a
lot of luck! It would have been smarter to plot the celestial LOPS on
a separate sheet at larger scale. In fact, plotting the whole trip at
such a tiny scale didn't make much sense either. I did that to fit it
all on one sheet. I should have just split it between two sheets. From
now on I'll use 1 mile per mm as my smallest scale, unless a single
long leg needs to be plotted.
My "almanac" was the USNO Web site, since I don't have a current book
almanac. I could have simulated its hourly tabulations, but the
contortions would have been unnatural, so I just cheated and let the
UNSO crank out each body's position at the time of observation.
Sights were reduced with HO 229. Using the message to be posted to the
list as my sight reduction form was surprisingly inconvenient. In the
future I'll do it on paper.
