Gallant Spirit
Well-Known Member
Keep a sextant onboard , but cheat a bit by using the astro plugin on CPN 
makes it really easy as the almanac is included
makes it really easy as the almanac is included
Call yourself a navigator?'
- Thread starter zoidberg
- Start date
Pye_End
Well-Known Member
Electrical storm?
prv
Well-Known Member
Have you ever had your mobile phone die because of one? Do you know anyone who has? I don't. I've carried a phone near-constantly since 2001 and I must have been in and around my share of storms in that time. Note I'm not asking about VHF radios and other installed yacht electronics, but referring to the fact that nowadays practically everything with a screen also has a GPS chip in it.
Nevertheless, on Ariam I have an old handheld GPS and portable depth sounder (and a 24-pack of AA batteries for them) in a metal tin in a deep locker. Not specifically against electrical storms but the closed tin would presumably help. One assumes a well-found boat crossing an ocean could afford the £50 for a similar backup.
Pete
Kukri
Well-Known Member
Yes but why are the RN using Plath sextants?
Daydream believer
Well-Known Member
Did anyone notice Boris J state in one of his early speeches just before or after election to PM that he would provide science funds for UK to have their own GPS system?
sorry do not want taint thread with politics but it did make me smile:encouragement:
sorry do not want taint thread with politics but it did make me smile:encouragement:
lw395
Well-Known Member
Found a couple in stores and thought they'd make a video?
lw395
Well-Known Member
Probably doesn't realise that the UK was very much involved in the current one.
vyv_cox
Well-Known Member
See post #10. The guy I contacted was collecting information, in some sort of official capacity, about total loss of signal in locations worldwide. His e-mails advised me that there are quite a few such places. When we lost GPS in Bay of Naples we had three alternative receivers but all were useless. I plotted our last position on paper but within a few miles we had signal again.
capnsensible
Well-Known Member
How often do you replace the old batteries with a new pack? Top tip. :encouragement:
Beelzebub
Well-Known Member
I've coped very nicely with the Davis Mk25 plastic sextant with an old Ebco as a backup. Thank goodness I never had to use the backup.
Fr J Hackett
Well-Known Member
Saw a Freiberg drum sextant in an auction at St Cast 3 days ago guid price €400 I thought about leaving a bid on it to give to our son, then I thought better of it.
Kukri
Well-Known Member
I’d say that’s expensive. I bought a Tamaya that has navigated (a) a Japanese WW2 submarine and (b) P&O’s “Oriana” for £109 on eBay, just to see if the 7x50 scope fitted my Plath, which it didn’t, so I gave it to a friend who was taking his Master’s ticket. It’s back at sea and back in business. So far as I can see, it’s almost identical to the Tamaya that you can buy today.
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prv
Well-Known Member
The expiry date for the pack is on my list, along with the equivalent pack in the grab-bag (for VHF, GPS, torches, and strobe), the food and water in the grab-bag, the main flares, the single flare in the dinghy, the lifejacket auto modules, and the lights on the lifejackets and Jon Buoy. So like everything on that list, the answer is "the winter before they expire".
Checking the list, it seems the current pack is good to 2023. I must have replaced it a year or two ago, which will be why the box of technically-expired batteries in my study for non-critical items like TV remotes is particularly full at the moment.
Since you ask :encouragement:
Pete
Frank Holden
Well-Known Member
At 38 seconds in the OP's vid..... why is that bloke looking at his watch after getting a MerAlt? Checking if its Gin'o'Clock yet?
sarabande
Well-Known Member
Doing a very small Sun-Run-Sun ?
PHN
Well-Known Member
The pinnacle in astro navigation IMHO is the Shackleton trip on board the James Caird from Elephant Island to South Georgia. Finding such a needle in a haystack of turbulent water and ice with very limited resources is close to a miracle. Worsley's navigational skills were amazing.
I have sailed that route myself under a whole lot better and much more comfortable conditions so it gives me at least some understanding how difficult it must have been for them.
I have sailed that route myself under a whole lot better and much more comfortable conditions so it gives me at least some understanding how difficult it must have been for them.
zoidberg
Well-Known Member
Worsley was the real hero on that trip IMHO...... but he wasn't a favourite of the King - just a 'tradesman'.
Frank Holden
Well-Known Member
Doing a very small Sun-Run-Sun ?
No accuracy in doing it that way ( if he is taking a normal morning sight or whatever) .... should be saying 'stop' to the person at the chronometer... ....
And his mate shouldn't need to bring the sun down to the horizon the way he is....
'Noon' should have been pre-calculated using the DR Lat.... set the altitude to what you have calculated... step outside... job done .
Doing that does let you read the lat directly off the arc.... if alt is 2' different to calculated alt then obs lat is 2' different to DR lat... easy peasy.
And what is the narrator doing with that horizon shade? At noon with that horizon? ..........
Seajet
...
The nearest I'll get to such skills is, I once got to touch the James Caird at the old, proper Earls Court Boat Show...I saw her on a lorry on the Horsham bypass just after.
This is exactly the sort of thing which winds me up a treat when people call footballers ' heroes ' - the story of Worsley and the James Caird should be much wider publicised, Jeremey Clarkson would do a good documentary.
Achosenman
Well-Known Member
Not true. Commercial aircraft still have inertial backup along with VOR DME and ADF, not forgetting radar.
Modern FMC’s calculate a very good fix even without GPS using VOR/VOR or VOR/DME or DME/DME. When they must revert to DR, it’s still pretty good and from my observations within a few miles after 10 hours at 550kts.