Considering these ideas of navigation.. What is your opnion on it?

[Jammer]

Originally Posted by wingssail

But all of this is not really the best way to spend your time. You really don't need to put much effort into covering the situation where all power is lost and all GPS systems have fallen out of the sky. Other comments have used sarcasm to point out the unlikeness of this eventuality. We started using GPS in 1993.

My parents live in a rural area prone to storms. In 2001 they purchased a 15 kw propane-powered generator set that mounts on a concrete pad, and had it wired up with a transfer switch and everything. I don't know how much it cost but it was expensive. Since then they have only had brief outages that would have been only a minor inconvenience.


Until the tornadoes last Thursday. There were 10, all small, and though they didn't get a direct hit, the transmission line that goes to the substation where their power comes from was shredded with dozens of very large poles down. Power came back on today.


Fortunately they've have the foresight to keep up on the preventative maintenance. Had they been without electricity, they would have had to leave their house and move in with us or something, because their house is dependent on electricity.


Complex systems have vulnerabilities. Maybe the way will never come when we lose GPS. I hope we never lose GPS. If we do, I want to have a better plan than "sail west until land becomes visible, hope the government there is friendly, and then sell my boat and cancel the rest of my journey once I'm in port."

[GrowleyMonster]

Originally Posted by fernandosmooth

Growley, do you get crawfish yourself there in nola or do you buy it?


edit: I dont know if offtopic conversations are allowed.

I think you can just start a thread in the appropriate subforum and mention me by putting an @ in front of my user name somewhere in the post and it will show in my notifications. Worsk that way on most web forums, anyway. But I am too lazy to go out and catch crawfish. Most of the time, too lazy to purge and boil them, too. We buy them at seafood sellers already boiled. Grocerie stores here usually have them but they overcook and don't season enough. For cooking we get frozen tails. You gotta peel a lot of crawfish to get enough for a gumbo or an etouffe. I try to put one tail in the bowl for every two I peel but I don't have much willpower when it comes to denying myself a crawfish tail already peeled and in my fingers. So figure about one in three that I peel makes it to the pot. So I have to peel an awful lot to get any amount of meat into the recipe. Frozen tails are not so much temptation and not so much work per pound of meat. We now return you to your regularly scheduled on topic thread.

[roverhi]

FWIW, had my GPS give me a position nearly a minute of longitude off actual position this past April off Monterey. Fortunately had a back up lat/lon gps and used that to find position and DR us into Monterey. I shut malfunctioning plotter down, stowed it away and bought another GPS plotter for the rest of the trip to Oceanside. When I got to O'side powered up the offending GPS and it was working and has continued to work fine ever since. Have no idea what got into it off Monterey but GPS units can and do screw up.

A real good idea to have a simple back up battery powered GPS. Keep it locked up in a metal case with several sets of uninstalled batteries. Never can tell when the Martians will land.

We did SoPac in the good old days with sextant, hf radio, quartz clock, almanac and tables. Navigated accurately enough to find the islands but it always seemed a miracle when the green hills and/or palm trees appeared on the horizon close to where they were supposed to be. Don't have any desire to have to depend on the old ways but still sail with a sextant that I've forgotten how to use.

[SteveSadler]

I agree, we're one lighting bolt, or rouge wave away from the 19th century.
a cheap sextant, almanac, and timepiece are almost all you need. Knowing how to use them takes practice 10 easy steps to celestial nav is my refresher book.
You'd best read it and practice before lightning strikes though.
The simplest fix is a noonsite. Dawn and dusk horizons aren't often clear.
Shoot the sun 20 minutes before zenith with a time, shoot the Zenith for Latitude, shoot the same elevation as the one 20 minutes earlier with time. Divide time in half and you get longitude.

[SeanPatrick]

Originally Posted by davefrediam

If anyone knows of a cheap resource for celestial tables I would be most interested!

https://navsoft.com/astronav.html


For £20 ($26 or €22) you can print almanac pages for any day of any year between 9999 BC and 9999 AD. And they are laid out almost exactly like the official Nautical Almanac.


Here is an example:
https://www.dropbox.com/s/fcwfsfy62v...manac.pdf?dl=0

[GrowleyMonster]

https://www.thenauticalalmanac.com/
https://www.nauticalalmanac.it/en/na...l-almanac.html
Download the Nautical Almanac for 2017 and 2018


The first link has a lot of other useful stuff besides the almanac. HO229, HO249, and other good stuff. I think the third link is a very good layout for the almanac pages. You can download PDF and print all, or just the pages you will need. However I think it is more convenient to just buy printed sight reduction tables and a printed almanac as it comes available. By the time you print out a couple of volumes of sight reduction tables and a complete almanac including increments etc, you have used up a ream of paper and a couple of printer cartridges and a bunch of your time. For a single short voyage then printing it out is more practical. Of course you can keep it on your phone or computer and refer to it as needed, but perhaps that is not in keeping with the idea of reliability in the face of complete loss of modern technology. Also the cost of the pubs is chimp change compared to the cost of a good used sextant.


Speaking of sextants,

https://www.celestaire.com/
A comprehensive source for all things related to celestial navigation. I got my first sextant from them, an Astra IIIB before the upgrade to LED light. Served me well until Katrina caused stuff to happen.


I also heartily recommend a copy of Bowditch, AKA "The American Practical Navigator". Deep reading but very authoritative. Download a free PDF first before you drop your coin on a printed copy. Like the full set of HO229, it is a bit bulky and it is the 600lb gorilla in the room, so to speak, at the navigator station in a small boat.

[GrowleyMonster]

BTW, having not bought a new sextant since Katrina, and no longer having one I could borrow due to the owner moving away, I thought it was time. Scored a Cassens & Plath, recently serviced, for $299 on Fleabay. Don't think just because you are on a budget, you are doomed to using a plastic sextant. There is a bustling used market. There are some dogs out there, but most will be just fine when you make a couple of adjustments and create a table of corrections if the limb has gotten warped. Also, always let your final adjustment of the micrometer be in the same direction so any gear lash in the teeth is accounted for. Some well worn sextants will have a bit of lash, or "wiggle". And if you see a nice low price on a vernier type sextant, don't think for a minute that it is greatly inferior to a micrometer drum sextant. A vernier sextant will still easily resolve to a half minute of arc if the marks are still clear and legible. There are a lot of 80 or 100 year old instruments out there that are not half dead yet, looking for a good home. Avoid the ones that the seller thinks are "rare" or have "collector's value", though. You want to use it, not display it. It is a tool, not jewelry. Just an old sextant that is probably still good to use, no more, no less. It is easy to pay too much! I saw several likely ones in just a half hour of searching, for well under $500. A couple of old Navy MkII's for less than $200. My strategy on Fleabay is I throw out lowball bids that I know have about a 10% chance of winning, because I know that there will be more chances to bid on similar, and sooner or later I will win. If you win every auction you bid on, you are bidding too high. And I don't allow myself to be unduly influenced by a reserve. Just cause it has a reserve of $400 doesn't mean it is worth $400.

[rickwest]

I sailed across the Pacific..to Asia
I had several GPS backups and old hand held..buy cheap used...a gps doggle for my laptop with Open CPN free mapping, I had two auto gps that when out at sea gave me lat/long of my location...I believe uour oven is a faraday cage...if all system failed I knew my location and I had a compass..food and water I would not die..just sail on a compass heading..you will hit land somewhere...

[longjonsilver]

i received my "Long Term Almanac 2000-2050 by Geoffrey Kolbe" It weighs only 239gms and comes complete with workcharts, examples, instructions and sight reduction tables. The Almanac must be corrected for any year after 2003 and so involves extra steps that would not be required for a current year almanac, however, one could print out the current year almanac using the link in post #111 or here: Download the Nautical Almanac for 2017 and 2018 . (Thanks Growley) Being light the book is also very compact, making it a good choice for a backup system, or any weight conscious sailor.

jon

[longjonsilver]

i've been working thru the Kolbe almanac. Not really much harder than other almanacs, but one or two extra steps -depending on how you count. Actually there are four almanacs in the Kolbe, years 2000, 2001, 2002, and 2003. You use one of the four depending on the year you are in. In 2018 we are using the almanac for year 2002. In addition, there is a correction for each cycle of 4 years. We have completed 4 cycles of 4 years now in 2018, so you must multiply 4 times the correction factor listed in the quadrennial column. You do this for the GHA and the Declination. Not that hard, but an extra step.
jon

[Adelie]

I received a PM from another member regarding my above post #6. Some of the issues raised are worth discussing generally so I have quoted portions of his/her PM below.

I have bought the Kolbe almanac and I notice that there are no moon or planet tables in it, just sun and stars. You mentioned "Moon almanac printed on waterproof paper for several years to come including laminated correction tables." Where can this be found? Would this just be a portion of the full almanac? I have printed out the moon correction tables. I am interested in the moon, because it is often visible in the daytime when the horizon is also visible. I like your idea of printing these things and laminating them. i suppose that this is to allow one to use a grease pencil or erasable marker and reuse them over and over?

I have found several different systems of sight reduction, and have printed them out and intend on laminating them when i decide which system works the best for me. i will be studying celestial nav this winter and hope to master sun, star, planet and moon sight reductions.
....

There is no easy way to create a long-term almanac for the moon or planets, the motions of both are fairly complex. In the long term (for me) I intend to create a long term almanac for the moon which tabulates moon position every 6hr with appropriate tables for interpolation. I expect some degradation in accuracy. I wouldn’t bother but the moon has 2 uses not found with other bodies:
A. It’s visible during daylight hours and can be used with the sun for a fix.
B. Because of its comparatively fast motion relative to all other bodies it can be used to reestablish accurate time if it is lost.

Developing a long term almanac for the planets could be done similarly but with little advantage over stars to make the effort worthwhile.

There is not actually an almanac with just moon ephemera in it. What I intended was that the moon portions of the almanac be extracted, consolidated and laminated. This should be some work but not excessive if using an inline or computer generated almanac.

Laminating tables or printing them on waterproof paper is intended to make them more durable on a boat for the long term (years/decades). For workforms I would print on waterproof paper and then laminate that. Lamination means the forms and plotting sheets can be used repeatedly rather than as consumables.

Yes, there are number of sight reduction methods, usually with multiple names and some with variations:

HO208, Driesenstock
HO211, Ageton. Var: Bayless, Pepperday
HO214 (9 volumes)
HO229 (6 volumes). Var: Schlereth (1 vol)
HO249, Aircraft tables (2 volumes + 1 supporting volume. )
Davies, NOA, Concise Sight Reduction Tables
Brown-Nassau Celestial computer (actually a page sized plastic slide rule from before when “computer” got its current meaning)
Bygrave (cylindrical sliderule)
LaPook (flat variation of Bygrave)
Hav-Doniol, currently being refined by the folks on NavList.
Weems

Plenty of others too from non-English sources.

For use on a small boat I would not use HO214 or HO229, too bulky unless I had a very large boat. The 1 vol. Schlereth would be fine.

[GrowleyMonster]

Originally Posted by Adelie

I received a PM from another member regarding my above post #6. Some of the issues raised are worth discussing generally so I have quoted portions of his/her PM below.



There is no easy way to create a long-term almanac for the moon or planets, the motions of both are fairly complex. In the long term (for me) I intend to create a long term almanac for the moon which tabulates moon position every 6hr with appropriate tables for interpolation. I expect some degradation in accuracy. I wouldn’t bother but the moon has 2 uses not found with other bodies:
A. It’s visible during daylight hours and can be used with the sun for a fix.
B. Because of its comparatively fast motion relative to all other bodies it can be used to reestablish accurate time if it is lost.

Developing a long term almanac for the planets could be done similarly but with little advantage over stars to make the effort worthwhile.

There is not actually an almanac with just moon ephemera in it. What I intended was that the moon portions of the almanac be extracted, consolidated and laminated. This should be some work but not excessive if using an inline or computer generated almanac.

Laminating tables or printing them on waterproof paper is intended to make them more durable on a boat for the long term (years/decades). For workforms I would print on waterproof paper and then laminate that. Lamination means the forms and plotting sheets can be used repeatedly rather than as consumables.

Yes, there are number of sight reduction methods, usually with multiple names and some with variations:

HO208, Driesenstock
HO211, Ageton. Var: Bayless, Pepperday
HO214 (9 volumes)
HO229 (6 volumes). Var: Schlereth (1 vol)
HO249, Aircraft tables (2 volumes + 1 supporting volume. )
Davies, NOA, Concise Sight Reduction Tables
Brown-Nassau Celestial computer (actually a page sized plastic slide rule from before when “computer” got its current meaning)
Bygrave (cylindrical sliderule)
LaPook (flat variation of Bygrave)
Hav-Doniol, currently being refined by the folks on NavList.
Weems

Plenty of others too from non-English sources.

For use on a small boat I would not use HO214 or HO229, too bulky unless I had a very large boat. The 1 vol. Schlereth would be fine.

Actually I think a long term Moon almanac is a pretty good idea, for the reasons that you stated. Shouldn't be too hard to do. That, with a long term Sun almanac combined with most any set of concise sight reduction tables would make for a nice, compact daylight sight solving kit. And no worries about star identification! All of this could be put into a fairly small booklet suitable for tucking into a sextant case. That would be a very low impact way for someone to get started with Celestial Navigation.


Brown-Nassau Celestial computer is not something I am familiar with. Too bad this is apparently no longer made. It would be an interesting tool to mess around with, maybe even a very practical one.

[Adelie]

Originally Posted by GrowleyMonster

Actually I think a long term Moon almanac is a pretty good idea, for the reasons that you stated. Shouldn't be too hard to do. That, with a long term Sun almanac combined with most any set of concise sight reduction tables would make for a nice, compact daylight sight solving kit. And no worries about star identification! All of this could be put into a fairly small booklet suitable for tucking into a sextant case. That would be a very low impact way for someone to get started with Celestial Navigation.


Brown-Nassau Celestial computer is not something I am familiar with. Too bad this is apparently no longer made. It would be an interesting tool to mess around with, maybe even a very practical one.

As mentioned, in my long term, I will be preparing a long term moon almanac. It will be part of a complete compact Celestial Navigation system including almanacs for all bodies except planets, sight reduction tables, worksheets, a plotting system and tables for some secondary uses of sextants.

The B-N was developed during WWII and was sold for a bit following but the USAF went with HO-249 so it didn't have a major buyer to help it establish market share. The NavList folks discovered this item several years ago including papers describing the underlying mathematics so were able to recreate the relevant pieces in PDF form. You can download and print all the pieces from them if you want and put your own together.

[NevisDog]

Growley: Let's say that Cassiopeia is directly above Polaris. Polaris then, is 40' lower than the celestial North Pole. So, a correction is needed to be added to HS to get the height of the celestial North Pole above the horizon. 90 degrees minus this corrected Sextant Height (HS) gives you Latitude. With an accuracy of a minute or less. In other words, within one mile North or South...

David M: Remember that Polaris rotates around true North at 89 degrees, 16 minutes.

Growley: Brain fart alert!!!! You don't subract HS of the North Pole (corrected height of Polaris) from 90 to get Latitude. It IS latitude.

Thanks all - this seems a really neat way to get latitude to within a mile or two (next time I'm in the northern hemisphere at least) without bothering with almanacs or sight reduction calcs (other than Height of Eye). But a quick scan of my 2018 almanac shows Polaris varying between about 89-20.1'N and 89-20.8'N, so maximum 40' from celestial north pole, in agreement with Growley. Have I missed something?

[GrowleyMonster]

Originally Posted by NevisDog

Growley: Let's say that Cassiopeia is directly above Polaris. Polaris then, is 40' lower than the celestial North Pole. So, a correction is needed to be added to HS to get the height of the celestial North Pole above the horizon. 90 degrees minus this corrected Sextant Height (HS) gives you Latitude. With an accuracy of a minute or less. In other words, within one mile North or South...

David M: Remember that Polaris rotates around true North at 89 degrees, 16 minutes.

Growley: Brain fart alert!!!! You don't subract HS of the North Pole (corrected height of Polaris) from 90 to get Latitude. It IS latitude.

Thanks all - this seems a really neat way to get latitude to within a mile or two (next time I'm in the northern hemisphere at least) without bothering with almanacs or sight reduction calcs (other than Height of Eye). But a quick scan of my 2018 almanac shows Polaris varying between about 89-20.1'N and 89-20.8'N, so maximum 40' from celestial north pole, in agreement with Growley. Have I missed something?

Only one thing, and I missed it too. Polaris is actually on the SAME SIDE of the Celestial North Pole as Cassiopeia. Compare their SHA and you will see what I mean.



But yes, definitely, 40', I double checked. Approximately. More accuracy than that would be wasted, due to the imprecision of eyeballing the angle of the line through the end star of Cassiopeia and Polaris to the horizontal, as well as observation error if shooting from a small boat. But if you had used 89deg 16' as declination and therefore a Polar Distance of 44', it would only make 4' of difference in calculated Latitude, anyway.