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Chris has a video where he demonstrates the process of converting an observed altitude into an intercept.

Chris has three videos dealing with basic, intermediate and advanced concepts of time. Very informative.

@@marcg1686 Thanks. I've been over these a few times but Equation of Time doesn't get a mention except to say it is included in the Daily pages box, page bottom alongside Sun and Moon transit times. What I have "worked out" for myself is this: taking an example from today's entry - Meridian Passage given as 1205 UT and EoT for Noon as negative 04':54". It seems plain that 6 seconds have been rounded off. For tomorrow (March 29th. 2024) the rounding is 24". This practice is evident in the Nautical Almanac for all recent years. I was a bit thrown when there is otherwise insistence on time keeping precise to the second. In the NA Auxiliary & Planning Data para.18 (page 260 in UKHO volume for '24) advice is given to adjust mean time by applying EoT. No mention that the time of Meridian Passage is perhaps already adjusted. It is I think a Grey area. I make solar compasses of the Bagnold type and prepare setting tables for these. It's a historic feature of these that individual operators make their own adjustment calculations for LAN at their DR position. The values for this (EoT) are taken from the Analemma. PS Are you The Captain Marc attending the past Sailings online classes ? If so Greetings. Many Thanks for the input 👍🏼

You look at your watch first. The reading stays on the sextant if you don't move the arm.

Congratulations!!

No offence, but I don't understand the point you're trying to make. If you use HO229 or HO249 Volume 2 and 3, the entry arguments are Lat, Dec and LHA. If you use HO249 Volume 1 the entry arguments are Lat and the LHA of Aries. The LHA is a prerequisite.

@@marcg1686 That is my point. With LHA you can constrain the number of possible triangles that need to be pre-computed down to something manageable. Very clever.

You needn't have a sextant to understand celnav. 10thman has a sextant, yet has never used it and completed a sight reduction.

😂 exactly! None of you have used the tools!! Where is 10th man by the way? Left the sinking ship?

@@Elder-Bear I'm not a flat earther. I have several sextants. I do understand how celnav works.

@NathanOakley1980 seems to be trying to debunk your expertise, yet he has Never used a sextant, that's a strange position to take isn't it?

I am not a flat earther either.

Well that isnt how celestial navigation works and you have sevetal flaws in your new way of doing it. Where do you get 60 nautical miles from? 60 nautical miles per degree is incompatable with a flat earth. The distances between lines of longitude wouldnt work. Right angle triangles aren't used in celestial navigation, but if you claim we can make one to the sun then i feel bad for those poor people being roasted at sun set. Way to many holes, back to the drawing board.

@@iveneverseensuchbehaviorin5367 I am still waiting for Jon, Any of Joakley's disciples, or any other Flerf to show me the derivation of the dip angle corrections in the nautical almanac (which they all agree are correct) WITHOUT using the Earth's radius. Going on 2 months now and no takers!

Circles of equal altitude only work on a globe, literally on a globe. They don't even work on the charts that navigators use. Why are there no maps available that show the flat earth?

@@marcg1686 OMG! Is it necessary for me to answer this nonsense? The surface cannot be spherical if there are circles of equal altitude over it!

@@JonBernhards66 I've an idea. I'll post three observations with the GPs of the celestial bodies observed and you plot them on a flat map and post a photo of the result to your Community tab. Think you're hard enough?

well with zero evidence and zero understanding of how celestial navigation works we'll just have to ignore you until you grow up.

​@@iveneverseensuchbehaviorin5367 clearly if our understanding of celestial navigation comes from this video with the fictious modeling of angles from curved adjacents then we would all be lost at sea

​@@njappboyUntil you come up with an alternative to the sight reduction process as has been employed for the last two hundred years, we'll just go with a globe with a mean radius of 3440.1 nautical miles.

@@marcg1686 stick with pretending you live on a ball and watch those government agency's computer generated images. "Sweet dreams are made of these...some of them wanted to be abused"

Nathan couldn't navigate his way out of a paper bag.

Deep down you know this insertion of assumed curvature is pure cognitive dissonance. Sure, if land is too close to you there can be a correction to adjust for the horizon. This has zilch to do with Earth curve and you both know it. Even the claim made of exaggerated curvature in the video is stated with hesitation. This is a purposeful slight at the fear of FE.

@@LBBstore My fear of FE is matched only by my fear of being savaged by a moist lettuce leaf. Until you explain how you would apply the dip correction on your space fritatta, we'll just go with a globe that has a mean radius of 3440.1 nautical miles.

@@marcg1686 Are you nuts? The dip correction is done based on the observer height to ensure the line from the observer to the horizon is PARALLEL with the FLAT WATER from observer to horizon to the GP of the star! If you are at an elevation of 0 THERE IS NO DIP CORRECTION. Again, if you lie you do realize you will be called out to show your claims in diagram form and once exposed you will never ever be trusted again! At 0 elevation there is NO dip correction…SHOW THE DIAGRAM of what is being done!

@@marcg1686 Are you stating it is not possible to remove the depression angle after taking an elevation angle with a Mariner’s sextant on a flat Earth? That would be an outright LIE… From Maritime Org: The correction is referred to as DIP and must always be subtracted from the observed altitude. In order to find the value of dip, the nautical tables must be entered with the height of eye of the observer above the sea surface. Once applied the observed altitude becomes the “apparent altitude” - Ok, so you remove the depression angle and correct your angle to ensure your baseline is PARALLEL with the horizon.. What’s the problem? You do realize if you lie you will be called out and exposed.

You're living on a globe. We've checked.

Hey Willy, you think Earth is flat. Prove it. Solve this celestial navigation problem using flat earth only. Should be easy. No flat earther will touch it, they all run away, deflect or give excuses. What will you do? Here are 2 real Sun sights. Find the observer's position. 1st Sun sight: February, 20 2010 17:26:26 UTC (GMT) Sextant: 40°18.2' Artificial horizon Sextant error: 0.0' Upper limb of the Sun 2nd Sun sight: February, 21 2010 00:16:02 UTC (GMT) Sextant: 24°04.4' Artificial horizon Sextant error: 0.0' Lower limb of the Sun No cheating now, you can't use globe science, only ''flat earth science''. Show all your calculations.

Oh btw there is no spherical right angle triangle when we take a sextant sight, in fact there is not even any kind of triangle in a sextant sight. The line of sight from the observer to the star is parallel to the line from the GP to the star so there is no triangle. There is only an angle between the horizon and the star. A spherical triangle exists in Celestial Navigation but it's a triangle on the surface of the globe as shown starting at 42:48. He beats it that Earth is a globe only for flat earthers that haven't figured yet that Earth is not flat, normal people already know that Earth is a globe. So when can I expect your flat Earth Celestial Navigation demonstration?

Nothing? I'll take it as it's imposssible to do flat earth celestial navigation.

Given your beliefs it's clear that you have the mind of a gold fish. Skip to 54:00 and try to identify the 'spherical right angle triangle'. Dunce.

" It is laughable." Yep it certainly was. You ran as far as you could. Zero attempt to make your point. (but truth be told you held a losing hand).

Level follows the curvature of the earth. Celestial navigation is created with the earth being a sphere. Celestial navigation wouldnt work if the eath was flat. Celestial navigation works, therefore the earth is a sphere. Your comment is meaningless, but if you want to understand the error of your ways i can help you.

'...a lot of straight lines...' Only two. The curved line to the horizon, the dip correction takes care of that and the curved line to the celestial body that is being observed. The altitude correction takes care of that. None of you 'tards can demonstrate celestial navigation on a notional flat earth. Why is that?

How close are the two objects to one another? I have several sextants. Two Davis MK15s and several metal ones. Mostly Cassens and Plaths. A sextant will do the job but calibrating one for such close distances could be an issue. Parallax at short distances can be an issue.

Your idea should work but a bit of work is required on the position calculations if they are at different elevations. I have used my Davis 15 to measure the horizontal angles between three lighthouses in the bay near where I live. What I did was to get their location coordinates and use maths to calculate my position, a process known as resection. That was done in the old days by a three-armed device known as a "station plotter" probably used in the 8th and 19th century by sailors making charts of the coastlines. All good fun!

@@karhukivi Sory about my crappy initial post (no editing). Continuing to work on this project. Will be using some device thus summer when the snow melts. I'm currently looking at a surveyors compas. I may do testing across a river with GPS knowns and see how accurate I can get. If my accuracy is less than acceptable, I will move to some other device. I continue to believe the sextant would do the job well. 10 minutes of accuracy. A sextant with a calibrated compas may be how I will proceed.

@@TimKaseyMythHealer Interesting project - let us know if it works, good luck!