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    Thread: Polaris
Post: RE: Polaris

My guess is the Polaris tables found in the USNO's nautical almanac are for long term use.  The Air Almanac Polaris table is recalculated every year.  Pub. No. 249 Polaris table is recalculated for ea...
LouisC The Sight Reduction process 1 2,800 12-26-2020, 02:19 PM
    Thread: New (to me) Ebbco
Post: RE: New (to me) Ebbco

BigBill, Is that the sextant that's similar to the "life-boat" sextant? It's pretty simple if the web pictures are correct. Is there a telescope or just a sight tube? Doesn't it feel good ...
LouisC General Topics Here 3 4,756 09-06-2020, 12:13 PM
    Thread: Celestial Nav problem I can't solve
Post: RE: Celestial Nav problem I can't solve

Hello All and especially Ray....welcome aboard! My guess is they're using Ho-229 to solve the problem.  Look at these pages from Pub. 229 Volume 2 page 339 to get Hc d and Z.  For interpolation of ...
LouisC General Topics Here 12 13,269 04-30-2020, 09:20 PM
    Thread: Questions
Post: RE: Questions

Joe, Thanks for telling us about the updated Bowditch. As to Haversins, can't help you much about that for finding the distance between two points. I use this formula for that; Distance = ...
LouisC General Topics Here 2 4,413 08-04-2018, 11:57 AM
    Thread: CN History
Post: RE: CN History

"History of.... is an excellent recommendation I read it a few weeks ago and enjoyed it. The writing is very understandable. SurvivorLibrary is an excellent site and the Librarian has provided man...
LouisC General Topics Here 1 3,460 07-16-2018, 11:35 PM
    Thread: LONGITUDE
Post: RE: LONGITUDE

Joe, Excellent video. I saw it quite a while ago. Very well done and a pleasure to watch. Concerning John Harrison (may his name be remembered forever) and his great work, I've often wondered if...
LouisC General Topics Here 6 8,566 07-07-2018, 01:09 AM
    Thread: Landfall procedure?
Post: RE: Landfall procedure?

Joe, It sort of is, but you're following a Sun line azimuth that would pass through your destination. It's pretty simple. Lou.
LouisC General Topics Here 10 16,039 06-09-2018, 12:49 AM
    Thread: USNO Astronomy site down?
Post: RE: USNO Astronomy site down?

They've replaced their batteries with weak ones- the site's "reachable" but extremely slow. It takes about 2 minutes to load this page- aa.usno.navy.mil/data/docs/celnavtable.php Well, better t...
LouisC General Topics Here 2 5,543 04-23-2018, 11:16 AM
    Thread: Video- Concise Sight Reduction Tables
Post: RE: Video- Concise Sight Reduction Tables

Bill, That's a great presentation you did. Pardon my lack of knowledge but can the Concise Sight Reduction be performed for all celestial bodies? I'll need to study your presentation since, so fa...
LouisC The Sight Reduction process 8 12,727 03-12-2018, 11:53 PM
    Thread: Analog or Digital time display
Post: Analog or Digital time display

Do you have a preference for time display?  Which do you like better?  Analog or digital? Do any of you use mechanical watches (not quartz)?  Now wouldn't it just be nice to have a Rolex GMT Ma...
LouisC General Topics Here 2 6,026 10-21-2017, 01:13 AM
    Thread: Electronic Sextant G-Stell
Post: RE: Electronic Sextant G-Stell

It probably wont work too well if the batteries die. Maybe there are backup instructions included on how to use a sextant? It would be curious to try it out. Lou
LouisC General Topics Here 3 7,474 07-12-2017, 11:18 AM
    Thread: Fun day on the deck
Post: RE: Fun day on the deck

BigBill, What's it like to take a sight through a bubble sextant? Must you hold very still to keep the bubble in the center of the circle? Lou
LouisC General Topics Here 4 7,404 04-04-2017, 02:12 AM
    Thread: Buy a sextant
Post: RE: Buy a sextant

Time has past but I got a Mark 15 off of Craigslist and the Davis AH (junk) to go with it for $75. The Mark 15 is small and easy to handle but not too accurate. It does get the job done and doesn't ...
LouisC General Topics Here 14 34,015 03-21-2017, 12:38 PM
    Thread: Beaufort scale
Post: RE: Beaufort scale

LouisC Wrote: (02-20-2017, 04:48 PM) -- Here's a link to a description of the Beaufort scale. My guess is if anyone here has been in a Force 12 we wont be hearing from them anymore. Beaufort sc...
LouisC Marine Weather 4 9,251 03-16-2017, 02:14 AM
    Thread: Beaufort scale
Post: Beaufort scale

Here's a link to a description of the Beaufort scale. My guess is if anyone here has been in a Force 12 we wont be hearing from them anymore. Beaufort scale- Picture & description (https://simpl...
LouisC Marine Weather 4 9,251 02-20-2017, 04:48 PM
    Thread: Altitude correction, Sun, with reflecting artificial horizon
Post: RE: Altitude correction, Sun, with reflecting arti...

The levels arrived earlier this week. They were placed flat 90° apart on a first surface mirror (1/8") thick. The fs mirror was placed on a 1/2" thick piece or Corian. My AH has 3 screws for adjust...
LouisC General Topics Here 9 23,932 07-30-2016, 11:29 AM
    Thread: Altitude correction, Sun, with reflecting artificial horizon
Post: RE: Altitude correction, Sun, with reflecting arti...

bletso Wrote: (03-31-2016, 10:37 AM) -- These are what I bought; http://www.amazon.com/Accuracy-Engineers-Workshop-Equipment-Building/dp/B014YHII8K?ie=UTF8&psc=1&redirect=true&ref_=oh_aui_detailpage_...
LouisC General Topics Here 9 23,932 07-12-2016, 10:39 AM
    Thread: Altitude correction, Sun, with reflecting artificial horizon
Post: RE: Altitude correction, Sun, with reflecting arti...

That's a solid looking arrangement of your AH. Can you give us a link to the levels? Lou
LouisC General Topics Here 9 23,932 03-30-2016, 11:40 AM
    Thread: Altitude correction, Sun, with reflecting artificial horizon
Post: RE: Altitude correction, Sun, with reflecting arti...

bletso Wrote: (03-27-2016, 09:16 PM) -- Get a 1st surface mirror, no ripples, no freezing, (well except for you).  Remember to level it.  $20 for a 6 X 6 1/4 thick glass unit from www.firstsurfacemir...
LouisC General Topics Here 9 23,932 03-29-2016, 01:26 AM
    Thread: Arrogant mathematicians
Post: RE: Arrogant mathematicians

It seems to me that those who love and understand math are the very ones who shouldn't be teaching it. It is probably an unwritten job requirement for math teachers to not have any personality and ze...
LouisC General Topics Here 3 8,167 03-05-2016, 03:15 AM
    Thread: Does anyone really shoot the Moon?
Post: RE: Does anyone really shoot the Moon?

Even on the hard with an AH the Moon isn't all that difficult to shoot. The right filter will make the work much easier. I think years ago there was some correction or figure for "irradiation". I...
LouisC The Sight Reduction process 8 15,706 02-27-2016, 01:38 PM
    Thread: Form- Doniol sight reduction
Post: RE: Form- Doniol sight reduction

We probably should provide the butterfly method if guys don't want to use a calculator. Lou
LouisC The Sight Reduction process 1 4,889 02-04-2016, 01:25 PM
    Thread: Buy a sextant
Post: RE: Buy a sextant

albyreto Wrote: (01-27-2016, 05:48 PM) -- Hi I have a Mark 15 plastic sextant and I want to buy a better one..  I've heard about Astra IIIb and Astra Professional... differences? what is the best...
LouisC General Topics Here 14 34,015 02-04-2016, 12:56 AM
    Thread: Doniol- Sight reduction
Post: RE: Doniol- Sight reduction

Slide rules are rather out of date but they don't require batteries! What I like about them is you can see a variety of answers linearly, such as 25nm divided by 3kn. I wish I had piles of the...
LouisC The Sight Reduction process 7 13,776 02-03-2016, 05:20 PM
    Thread: Davis Mark 15 sextant- wanted
Post: RE: Wanted- Davis Mark 15 sextant

The Mark 15 is ok. Not super accurate but good for learning the art and it won't rust.
LouisC Equipment- Wanted or for Sale 4 10,661 02-03-2016, 03:22 PM
    Thread: Doniol- Sight reduction
Post: RE: Doniol- Sight reduction

Here are the haversine tables up to 179° 58'. The decimal point was eliminated to save space on the pages.  Just assume there's a decimal point in front of each of the 4 digit numbers. Only the ...
LouisC The Sight Reduction process 7 13,776 01-20-2016, 03:19 AM
    Thread: Doniol- Sight reduction
Post: RE: Doniol- Sight reduction

I used Libreoffice Calc to make some haversine tables up to 179° 58'.  Beginning at 178° 37' the haversine figure goes to .9999 all the way up to 179° 59' I'll post them here tomorrow. Lou
LouisC The Sight Reduction process 7 13,776 01-19-2016, 10:05 PM
    Thread: Doniol- Sight reduction
Post: RE: Doniol- Sight reduction

Fred_B Wrote: (01-14-2016, 11:58 PM) -- Yes, I'm up for it.  The haversine tables I got off the web somewhere last year.  Bowditch 1972 vol. 2 has 'em also.  You have to buy the 1972 edition now.  Co...
LouisC The Sight Reduction process 7 13,776 01-16-2016, 02:35 AM
    Thread: Doniol- Sight reduction
Post: Doniol- Sight reduction

Anybody want to talk about their experience in doing a Doniol sight reduction? Do you HAV your Haversine tables? Louis
LouisC The Sight Reduction process 7 13,776 01-13-2016, 02:23 AM
    Thread: Pub. No. 249
Post: RE: HO-249

Doniol is a simple method and over the past few months I have given it a try. Initially, it was a somewhat confusing and I got the Haversine tables from Bowditch 1972 Vol. 2. I have not solved for Z...
LouisC General Topics Here 3 7,324 01-13-2016, 02:18 AM
    Thread: Good sight of Venus on January 12, 2016
Post: Good sight of Venus on January 12, 2016

Much to my delight I noticed Venus this morning at UTC 07:00 Rather than freezing outside a dish of water was placed on the window sill and I got 3 good sights of Venus. Now if I had referred to thi...
LouisC General Topics Here 0 3,292 01-13-2016, 02:13 AM
    Thread: Instructions- Sun sight reduction
Post: RE: Instructions- Sun sight reduction

That Sun sight reduction write up is excellent!
LouisC The Sight Reduction process 1 4,435 12-30-2015, 05:11 PM
    Thread: Sight reduction- Spreadsheet
Post: Sight reduction- Spreadsheet

I'm lazy and sometimes am not inclined to work with paper-and-pencil so I use this spreadsheet; Sunsight reduction spreadsheet (http://thenauticalalmanac.com/Sunsight.xls) I put the program on m...
LouisC General Topics Here 0 3,389 12-23-2015, 02:39 PM
    Thread: Determine Latitude- method
Post: RE: Determine Latitude- method

CelNav57, did a Latitude shot the other day following your AH method for Latitude, for fun, and it worked out very well. Good write up. Louis
LouisC General Topics Here 4 9,665 12-18-2015, 02:12 AM
    Thread: Limb to use- Upper or Lower?
Post: RE: Limb to use- Upper or Lower?

I have made many superimposed Sun sights with an AH. Why? Because the lake I was using as an AH had a light breeze blowing on it and the water rippled so much selecting an UL or LL was not going to ...
LouisC The Sight Reduction process 11 18,798 12-18-2015, 02:08 AM
    Thread: Pub. No. 249
Post: Pub. No. 249

Pub. No. 249 makes life easier as I only need about 10 degrees of Latitude Same Name sheets.  Guess what time of year we sail? We do mostly Sun sights and Stars using Vol. 1. The celestaire Vol....
LouisC General Topics Here 3 7,324 12-15-2015, 03:15 AM
    Thread: Writing down sights
Post: Writing down sights

Index cards are very handy for writing down shots- it's what I use.  Maybe there's a quicker and easier way- what do you write the sights down on? Lou
LouisC The Sight Reduction process 2 5,052 12-14-2015, 05:01 PM
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