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Catalina/Capri 25/250 Sailor's Forums

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I finally bought a sextant, C.PLATH

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Ben - FL
Admiral

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880 Posts

Initially Posted - 09/29/2002 : 13:34:31

I finally gave in to desire and bought a used C.PLATH HAMBURG sextant.
This morning I drove to the beach and took my first Sun sight. However I don't have the almanac so I can't do the DIP or any other calculations. I did find a website that does some of the calculations at [url="http://www.tecepe.com.br/nav/almanac.html-ssi"]Online Almanac[/url].
So does anyone out there have any experience with celestial navigation or know of any other references on line. I would like to find a soft copy of the Nautical Almanac and Sight Reduction Tables.
<img src="http://www.members.aol.com:/benraye/pictures/sextant.jpg" border=0>

Safe voyages,
Ben, FL s/v Chick-a-pea C250wk

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Tray
Navigator

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Namibia
224 Posts

Response Posted - 09/29/2002 : 15:10:24

Ben,

I might have an extra almanac at work. I'll email you from work tomorrow.

Do you plan on using the old manual calculations, or a computer program? In my prime I could get a star fix within 3NM of GPS.

Tray
C-250WB #554
"Weeny Bean"

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Ben - FL
Admiral

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880 Posts

Response Posted - 09/29/2002 : 20:12:50

Ahoy Tray!

I was wondering whose brain I could pick apart about this. <img src=icon_smile_big.gif border=0 align=middle>
Didn't think submariners did celestial navigation.

I would love to have an old NA. I was just going over that website and it says that I can use an old almanac for the yellow pages as some of the data is not included, but that it does not change from year to year.

Found a couple of old books on the shelf here at home. One is <u>Practical Celestial Navigation</u> by Tom Bottomley. The other is <u>Calculator Navigation</u> by Stafford Campbell. So I'll be having to brush up on my trig a little.

BTW, is your 250 still in St. Marys or did you get it moved to NAS JAX? If so, we'll be within about six miles of each other.

Safe voyages,
Ben, FL s/v Chick-a-pea C250wk

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Tray
Navigator

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Namibia
224 Posts

Response Posted - 09/29/2002 : 20:44:56

At the moment, she's in the slings at Point Peter, but I'm launching tomorrow and going back to St Marys. I finally got a slip in Fernandina, and I'll be moving there next weekend, weather permitting.

When I first joined up, submarine quartermasters had to know celestial nav, but I think it was a carry over from the old days. We can't exactly hook the sextant up to a periscope, but it was on our rating exams, so I practiced when I could.

I let you know what I find leftover at the office.

Tray
C-250WB #554
"Weeny Bean"

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allencl
Navigator

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USA
143 Posts

Response Posted - 09/29/2002 : 23:24:54

This is passing along a recommendation of somebody else's, rather than my own personal experience.

In My Old Man and the Sea (http://www.amazon.com/exec/obidos/tg/detail/-/0060976969/qid=1033356516/sr=1-1/ref=sr_1_1/104-9144716-4819960?v=glance), which I did read and enjoy, the authors David and Daniel Hays talk about the only good book ever written on the subject. It is described as very readable and very practical. This is Mary Blewitt's Celestial Navigation for the Yachtsman (http://www.amazon.com/exec/obidos/ASIN/0070059284/qid=1033356380/sr=2-2/ref=sr_2_2/104-9144716-4819960).

Have fun,

-Chris on "SPIRIT" C25 SR WK #5644

Edited by - allencl on 09/29/2002 23:27:57

Edited by - allencl on 09/29/2002 23:28:59

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mqp
1st Mate

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USA
46 Posts

Response Posted - 09/30/2002 : 09:58:22

I seconded Chris' recommendation of Mary Blewitt's book. It's very readable and has clear explanations.

--Minh

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Ben - FL
Admiral

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880 Posts

Response Posted - 09/30/2002 : 19:40:24

Hey Thanks for the links to the books!

Progress report:
I took four Sun sights this morning as I wrecked my truck this morning in a frog strangling downpour during the predawn hours and didn't go into work. But the Sun peeked through for a short half hour.

I used a bowl of water on the lawn for an artificial horizon. Then focused the eyepiece on the bowl with the reflected Sun in it and brought the real Sun down until the two matched. Then I instantly look at the seconds on my watch, then minutes and the hour. My GPS said I was 21' above sea level, so I used that for my DIP. After doing four sights I plugged the numbers into the program referenced above. I got four LOPs and a fix. But it was 1300nm off from my AP of 30n 082w.

I did divide the Hs by two because of the artificial horizon. I then ran the numbers again, halving the Index Error also and still came up 1300 mi off.

Any suggestions as to what the cause may be? The program says it does the Simidiameter. And watch error is only +1 sec.

Safe voyages,
Ben, FL s/v Chick-a-pea C250wk

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Buzz Maring
Master Marine Consultant

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USA
1775 Posts

Response Posted - 10/01/2002 : 12:03:24

Progress report:
I took four Sun sights this morning as I wrecked my truck this morning in a frog strangling downpour during the predawn hours and didn't go into work. But the Sun peeked through for a short half hour ... After doing four sights I plugged the numbers into the program referenced above. I got four LOPs and a fix. But it was 1300nm off from my AP of 30n 082w ... I then ran the numbers again and still came up 1300 mi off.

Any suggestions as to what the cause may be? - Ben

Holy cow Ben! You wrecked your truck, couldn't go to work, but you stayed home to take sextant readings between the downpours?! I think you must have hit your head in the accident! Seriously, I hope you're OK, but don't tell your Admiral about your sextant sightings ... she'll likely send the white-suited men with a straight jacket to pick you up! (Maybe they'll let you take your sextant with you to the sanitarium.)

Buzz Maring, C-25 SK/SR #68, "Freya"

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Ben - FL
Admiral

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880 Posts

Response Posted - 10/01/2002 : 20:14:11

Hey Buzz,

It was only my 2000 GMC Sierra truck, not my C-250!<img src=icon_smile_big.gif border=0 align=middle>

On the way to work I hit a downpour on the [url="http://www.mikestrong.com/dames/"]Dames Point Bridge[/url] and started hydroplaning. Went back and forth four times before the @$$ end finally got ahead of me and ended up with my back bumper hanging over the outside wall! Fortunately nobody else was involved and I lived to tell about it. <img src=icon_smile_blackeye.gif border=0 align=middle>

Safe voyages,
Ben, FL s/v Chick-a-pea C250wk

Edited by - ben - FL on 10/01/2002 20:26:33

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Tray
Navigator

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Namibia
224 Posts

Response Posted - 10/02/2002 : 16:53:31

Ben,

I've got a book for you. Email your mailing address to me, and I'll send it out.

Tray
C-250WB #554
"Weeny Bean"

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ssteakley
Captain

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USA
467 Posts

Response Posted - 10/02/2002 : 22:53:58

Ben,
I am interested in buying my first Sextant and have spent the night searching e-bay...one thing in reading the numerous articles is making sure the sextant has been recently calibrated, so some error may be due to the need to have the instrument calibrated by a professional. I want to have one just to understand celestial navigation just in case I am out there some day and the GPS dies,
Steve Steakley

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Ben - FL
Admiral

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880 Posts

Response Posted - 10/03/2002 : 20:42:47

As I understand it, the only error in the sextant is the index error (IE) which is taken into account during the calculations. The IE is read by lining up the horizon (or a window sill) in the mirror and the glass until it is continuous. Then read the scale. If it reads 0 deg. O min. then there is no error. If there is say a plus 4' error then you subtract 4' in your calculations. Which I did do.

I'm off work for another three day weekend so I am hoping to do some more practice sights and some more reading on the matter. Like you said, just in case I need it some day. And it makes life more interesting. <img src=icon_smile.gif border=0 align=middle>

Safe voyages,
Ben, FL s/v Chick-a-pea C250wk

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bren737
Captain

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291 Posts

Response Posted - 10/03/2002 : 22:13:28

Steve,

If the GPS dies, might I suggest rather than going through the trouble of purchasing and learning to use a sextant, you simply steer for the big "S" on your compass until you come to the dam. When you see the dam, stop, as you can go no further. Walk down the back side of the dam to the Corps of Engineers' office and call for a ride back to the marina. Much easier than messing with old "technology".<img src=icon_smile_wink.gif border=0 align=middle>

(Sorry, I simply could NOT resist the temptation. . . I'm really just kidding. I admire your dedication to the true sailing tradition. It's something I hope to also do at some point, just simply the proverbial "too busy" at this point)<img src=icon_smile_big.gif border=0 align=middle>

Got any more of those "accident" pictures?

Bren Peterson
C250WB, #642, "Ruah"
San Antonio, TX

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Derek Crawford
Master Marine Consultant

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USA
3324 Posts

Response Posted - 10/03/2002 : 22:27:08

I admire anyone who can master celestial navigation! However, when we brought the "Big Cat" from Key West to Port Aransas, Texas, we had the nav. station hard mounted GPS and all 3 crew had their own handheld units. Plus we carried 24 spare batteries...I still don't think that was overkill! We also plotted DR positions every hour. Nobody on board knew celestial!
Derek

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