Celestial Navigation, Episode 4: Calculating Local Hour Angle (LHA) and the Assumed Position (AP)

[@causewaykayak]

It is well said that explanation from a real master eases the passage of learning. That was so well done. Thank you.

[@kpeinthoven]

I have spent a lot of COVID time trying to teach myself celestial nav. I find this the best explanation so far. I like the approach of explaining the big picture before diving into the tables. Most other sources dive into the tables without explaining the big picture and I have struggled to understand what different terms actually represented. Keep up the great work.

[@thenavstation]

Thanks and keep after it! The more one gets used to the steps involved, the easier it is to go back and make some sense of the theory.

[@parkerssafes]

Same here!

[@AJ-hl5rd]

I agree! Nothing better than a good classroom instructor.

[@GMT-plus-seven]

​@@thenavstationthanks for sharing your knowledge. "When the student is ready, the teacher appears."

[@OzDiGennaro]

i appreciate NavStation's careful analysis and repetition. It makes me understand and come along. thanks, Andy

[@FlatEarthMath]

I can't tell you how much enjoyment I'm getting out of this series. I'm a geometry guy (High School math teacher), so you're speaking my language. Very clear explanations, and I love your approach. There are probably a million different ways to teach celestial navigation, but your approach must have taken a bit of time in planning, and it really pays off. "Big picture" first! 🙂

[@thenavstation]

Thanks for your comments. Let me know if anything isn't clear and I'll do my best to explain it.

[@tonymcflattie2450]

All the flat earth debunkers are buying sextants and learning celestial nav, me included! Ps, you are gonna need arrrgghhhh for that!

[@tenoveira432]

Excellent! Teaching the 30000f altitude, then explaining the details is a good way to explain. I was looking for celestial navigation and found your series of videos. Thanks for your dedication and patient to transmit this art!

[@luiscelma2109]

Thank for the explanation very good material

[@lady38155]

So well set out, very enjoyable. Thank you.

[@mariepierremaingon4487]

Thank. you for your step by step clear explanations!

[@thenavstation]

Thanks for watching!

[@peterfynn]

Very confusing at minute 14:33. Why isn't LHA in the second example of the Eastern hemisphere 50 degrees? The actual angle between your position and the sun's. ie. 360 - 310 = 50. Thanks for great explanations - very helpful.

[@marcg1686]

GHA is always measured westward. LHA is also only ever measured westward AND only ever FROM the observer to the GHA. In the second example we have the observer located E 20°, so his LHA starts at E 20°, goes westward to the prime meridian and then all the way westward till it intercepts the longitude of the celestial body, thus 20° plus 290°.

[@alvelijr]

Well done Really enjoying the coarse..

[@josephlai9759]

You explained it very clearly and patiently. Just a question: will it be the same process in the Southern Hemisphere?

[@thenavstation]

The process is the same, but it is a big help to draw yourself a diagram to make sure you are following the rules!

[@Navisworker]

Was GHA the measurement taken from the sextant?

[@thenavstation]

GHA is a measurement of how far to the West of the Greenwich Meridian (O degrees of Longitide) the body is located at the specific time of the sight. It is found in the pages of the Nautical Almanac based on month, day, and time for the particular body.

[@doglao1236]

thanx

[@kellycarpenter9350]

Yes !

[@stephenrichie4646]

Okay, it’s starting to come back 🤔

[@peterfynn]

Got it! Sorry - the LHA is from me to the body (sun), not the angle between them - keep going clockwise!! OOOps!

[@thenavstation]

And that points out that the best way to approach celestial is to not fully trust your work until you've had a chance to essentially "talk it out with yourself" to see if it makes sense. I've made plenty of mistakes and am always willing to scrap a sight and take another one, or completely rework the sight reduction.