Setting the time on a chronometer - how?

[Refueler]

Is it OK to ask if there is an android app or a program for my PC that will do the maths for me - or is this cheating?
For the purposes of YM Ocean I assume that one has to show all the working and not use an electronic shortcut?

TudorSailor

Its actually not hard to create a Spreadsheet to do it ... OK - you still need the tables. But that's not a bad thing as then you don't lose the manual skill to work it out.

I still have my workbooks .... where each page had a standard table of working set out.

 

[emandvee44]

Is it OK to ask if there is an android app or a program for my PC that will do the maths for me - or is this cheating?
For the purposes of YM Ocean I assume that one has to show all the working and not use an electronic shortcut?

TudorSailor

Yes - go to backbearing.com - it is all there ! (also elsewhere on the internet)
M.

 

[Refueler]

Plain Nav app Android ... free :

Nautical Calculator – Apps on Google Play

Navigation Calculator – Apps on Google Play

Nautical Astronomy – Apps on Google Play

Sight reduction – Apps on Google Play

>>>>>>>>>>> and so on

 

[GHA]

Is it OK to ask if there is an android app or a program for my PC that will do the maths for me - or is this cheating?
For the purposes of YM Ocean I assume that one has to show all the working and not use an electronic shortcut?

TudorSailor

The opencpn plugin is pretty good, nice visual LOP, if it helps you to learn then it's not cheating

Celestial Navigation Plugin
Celestial Navigation [OpenCPN Manuals]

 

[tudorsailor]

By chance I saw a play about Shackleton this week. This prompted me to look to see how Worsely managed to navigate from Elephant Island to South Georgia. I found a publication on the net that examines Worsley's log book and records. Much to my surprise he managed to take sights and then do all the complete working out whilst in a gale. For anyone interested, it is recorded in https://www.canterburymuseum.com/as...-James-Caird-on-the-Shackleton-Expedition.pdf
The article recounts how Endevour set out with 24 chronometers and Worsely took the best remaining one to South Georgia.

Amazing!

TudorSailor

 

[Skylark]

Is it OK to ask if there is an android app or a program for my PC that will do the maths for me - or is this cheating?
For the purposes of YM Ocean I assume that one has to show all the working and not use an electronic shortcut?

TudorSailor

It’s not only “cheating”, it’s also Heresy!

It really is not difficult to reduce a sun sight and time to a position line. Once the “penny has dropped” you’ll do it, on plain paper (no template required), in just a few minutes. Also, it will be obvious if you’ve made a error while working through the process, something not possible by pressing buttons on a keyboard and believing in the result.

There are plenty of experienced posters on here to offer support and encouragement while learning.

It is possible to derive Long from a MP but it’s controversial at best. Bowditch shows 2 methods.

It relies upon being able to precisely determine the time of the point of maximum Hs and this isn’t easy. Taking a number of sights, say 20 mins before and after predicted MP enables you to plot the results and make a mathematical estimation. Long by MP is not taught within the RYA Ocean Shorebased course.

 

[GHA]

It’s not only “cheating”, it’s also Heresy!

Tudorsailor, as relative newcomer in learning celestial nav I have to disagree with that, 110%. When learning it can be so helpful to see the position line from lots of sights straight away without having to go through all the maths as well, really handy. Then the next day after you've got confidence in just taking sights and feel comfortable that they won't be too far off you can start on the next step. Doing the whole thing start to finish just means any step of the way could contain errors and you have no idea where. Nothing wrong whatsoever in having some stabilisers on your bike at the very start.

 

[Skylark]

If it helps people to pick up a sextant and take a sun sight then I can’t argue with suggestion. But, the maths isn’t hard, it is very, very basic trigonometry. Sight Reduction tables are very similar in concept to sin, cos and tan tables as taught to school kids.

I’m sure that with a globe, a golf ball (aka the sun) and a few simple diagrams an instructor could outline the procedure in half a day, max.

Reducing a sight and time to a position line is an extremely satisfying and rewarding process. I don’t see the point in using a calculator, but I readily acknowledge that many do, but I still live in a era of wearing a mechanical watch (ironically no use whatsoever for navigation ?) and ink pens.

 

[Refueler]

Funny ... both myself and my business partner use Ink Pens. I keep meaning to have my Mothers Waterman No 7 serviced. It was left to dry out and now the lever is stuck, nib is clogged. Shame - its a nice pen and has a lot of real value as well as family sentimental.

But even though mental arithmetic is a strong ability of mine - I have succumbed to a calculator !

Reminds me - I must go find that Ti59 !!

 

[AntarcticPilot]

Funny ... both myself and my business partner use Ink Pens. I keep meaning to have my Mothers Waterman No 7 serviced. It was left to dry out and now the lever is stuck, nib is clogged. Shame - its a nice pen and has a lot of real value as well as family sentimental.

But even though mental arithmetic is a strong ability of mine - I have succumbed to a calculator !

Reminds me - I must go find that Ti59 !!

I was taught mental arithmetic back in the Dark Ages, when the teacher would rap out a sum and we were expected to snap the answer back. It didn't make me good at it! I can do it, but a calculator is faster for all but the simplest arithmetic.

For me, it's about understanding WHY a method works. I haven't done celestial navigation in anger, but I understand the principles very well, and have no doubt I could obtain a position line from first principles - I've worked through the theory and it's not difficult (I have a strong background in spherical trigonometry). Having that understanding, I'd quite happily use a canned solution, be it a work sheet, spreadsheet or app - they all automate a procedure that leads to the result; they just use different technologies. Even pencil and paper reckoning of all but the noon sight for latitude hides a lot of trigonometry behind the apparently simple procedure - computers do the same, but avoids even having to look up tables! Now, many people don't have the background to follow the trigonometry, but they are perfectly capable of following a procedure and getting the right answer. I don't think it matters whether the procedure is pen and ink, calculator, app or whatever - they are all simply procedures that reduce the mathematics to a simple series of steps.

 

[Skylark]

Funny ... both myself and my business partner use Ink Pens. I keep meaning to have my Mothers Waterman No 7 serviced. It was left to dry out and now the lever is stuck, nib is clogged. Shame - its a nice pen and has a lot of real value as well as family sentimental.

I imagine that it would be well worth while getting it serviced. Nice pen. One of my favourite’s is a Mann 100, centennial issue.

My handwriting is dreadful but using an ink pen makes it almost legible ?

No doubt someone will post that handwriting is obsolete and we should be dictating into a smart ap to convert spoken word into new, keyboard abbreviated English ?

 

[Refueler]

If I write with a ball point pen - my writing is atrocious ... my father was the same. Believe me - far worse than a Doctors prescription ...
But a fountain pen seems to make it better.

Yes my Mothers pen was valued at over 400 pounds when I investigated having it serviced - I did not know she had it, it was in her Jewellery box after she passed on, along with my Fathers medals etc.
I then found out she was given it as a young teenager by her Grandmother, who had also given her, when a small child, a porcelain doll dressed in WW1 parachute silk. Unfortunately my Brother, also passed on, who was an alcoholic sold the Doll and one of my Fathers medals after she died before I could stop him.

I've watched videos about servicing Waterman pens ... but I'm not willing to risk my having a go. One day I will have it professionally serviced.
The agents that looked at it those years ago - mentioned it was a special issue, it has a black top with gold band, with an individual metal clip with CS engraved into the upper part, plus the gold marbled body has an inscription that has partly worn away that I can no longer read fully. I never realised it was a Waterman because of that clip. But they confirmed it was.

 

[Kukri]

Nice pen. Teaching grandma, no doubt, don’t force the lever as the sac will be hardened. Cold water with a drop of household ammonia in it will eventually get the dried ink out. Yes it needs a professional repair. I’ve been pleased with this chap:

Battersea Pen Home: Vintage and Modern Pen Specialists

 

[TLouth7]

Sight Reduction tables are very similar in concept to sin, cos and tan tables as taught to school kids.

Similar to what? I had never heard of a sin table until I read TudorSailor's quite excellent paper (post #85 above).

I find it very funny that because these days the purpose of astro nav (apart from an academic interest) is to provide a backup in the case of failure of electronics, it is necessary to have a procedure that does not rely on anything electrical. By contrast when it was the principal form of ocean navigation immediately prior to GPS people were quite happy to use eg a programmable calculator. I guess when you are used to low precision the idea of relying on DR as a backup isn't so daunting.

 

[Refueler]

Similar to what? I had never heard of a sin table until I read TudorSailor's quite excellent paper (post #85 above).

I find it very funny that because these days the purpose of astro nav (apart from an academic interest) is to provide a backup in the case of failure of electronics, it is necessary to have a procedure that does not rely on anything electrical. By contrast when it was the principal form of ocean navigation immediately prior to GPS people were quite happy to use eg a programmable calculator. I guess when you are used to low precision the idea of relying on DR as a backup isn't so daunting.

Astro even today is still the standard .. GPS has not superceded that fact.

Similar situation to Digital Charts / ECDIS ... paper charts are still the standard. If a ship wants to 'rely' on ECDIS - it is required to have a second full system as back-up, but still carry the paper.

What in practice has happened - navigators have over time left the sextant in its pretty case in the cupboard and only dust it off for inspection. Bridge has multiple GPS units .....

I can remember one vessel I visited and while waiting next lightering barge ... asked the 3rd Mate if he ever used the sextant ... he didn't even know where it was ... I then looked in cupboards and found it. I tyook the box out and opened the lid. He went to lift it out .... I stopped him. Lifting a sextant out is done with one hand and by fingers holding the middle part of the frame - so its a straight lift out. He went to 'twist' it out.

Sad.

 

[tudorsailor]

Here is more heresy.......... I am checking the accuracy of two watches (a Tissot vs Suunto Core) with a neat app called watchcheck that is free on Android
WatchCheck - Apps on Google Play

TudorSailor

 

[Uricanejack]

Gosh! I mistakenly thought that by noting the time that the sun was highest that one could work out the time difference from the Greenwich meridian and hence one's longitude.

Back to Mary Blewitt...

TudorSailor

Not a mistake. You can. Problem is accuracy, getting an accurate time of the sun at its maximum altitude is difficult. The sun moves quickly. So the longitude changes very quickly.
So the practice of taking an earlier observation and running it up to noon as a running fix was developed. To increase accuracy.

In the close enough category. A method printed in the instructions for a Davis.

Before you take your meridian passage at apparent noon.

Set the sextant to a chosen altitude a bit less than what you expect noon altitude to be. Take an accurate time when the sun is at this Altitude.
Or just take an altitude and time.

Just after apparent noon.
Set the sextant to the same altitude as prior to noon. Observe sun until at same altitude and take the time.

Divide the difference in time and you will have a more accurate time for apparent noon which you can use as you describe. To determine longitude.

It’s not quite accurate. Two problems, both your boat and the sun continued to move. During the interval.
But it’s close enough for horse shoes and hand grenades.