5 ms·

Curious how navigation at night was not possible without expensive equipment, sounds like they were relying only on starts in the morning and evening? Are the m

Curious how navigation at night was not possible without expensive equipment, sounds like they were relying only on starts in the morning and evening? Are the measuring something like angle of those morning/evening stars or their set/rise times with respect to the sun?

_yb2s 2y ago
It is not true- the authors sound very inexperienced with celestial navigation. There are many ways including the lunar distance method to get a position at night with regular equipment. The math is more complex than a simple noon solar sighting, but it can be done with just a regular cheap plastic sextant and a watch. It’s also no big deal to go 12 hours with no position. If you know your speed and heading you can accurately estimate your position much longer than that. Overall, they also made it sound almost impossibly difficult for a large team of professionals, when solo and otherwise short handed recreational sailors have been reliably sailing around the world with celestial navigation for more than a century- through all possible conditions.
- danielvf 2y ago
  Note that they were staying roughly 2 miles within the actual track, while having the bulk of the work being done by a combo of officers and newbs that they had just trained. That's high accuracy standards for celestial nav, not even counting that this is most of other people's first time doing this in anger.
quercusa 2y ago
And just how expensive is a bubble sextant?
- wrycoder 2y ago
  I have one I paid $150 for. But bubble sextants are usually only used on aircraft.
- ianburrell 2y ago
  I discovered that real Tamaya marine sextants are available on eBay for $100-150. They were 30x that new. My understanding is that the sextants are coming from breaker yards in India where the sextants were left on ships and salvaged.
throw0101a 2y ago
> Curious how navigation at night was not possible without expensive equipment, sounds like they were relying only on starts in the morning and evening? As a sibling comment notes, it is possible. There are tables for lunar distance: * https://thenauticalalmanac.com/Lunar_Distance_Tables.html https://thenauticalalmanac.com/Lunar_Distance_Tables.html * https://en.wikipedia.org/wiki/Lunar_distance_(navigation) https://en.wikipedia.org/wiki/Lunar_distance_(navigation) * https://www.starpath.com/resources2/brunner-lunars.pdf https://www.starpath.com/resources2/brunner-lunars.pdf The planets Venus, Mars, Jupiter, and Saturn can be used, as well as several dozen planets (lookup tables in an almanac) * https://en.wikipedia.org/wiki/Nautical_almanac https://en.wikipedia.org/wiki/Nautical_almanac * https://thenauticalalmanac.com https://thenauticalalmanac.com Two US military videos explaining the theory (ground points/GP, circle of position, etc): * USAF: https://www.youtube.com/watch?v=UV1V9-nnaAs https://www.youtube.com/watch?v=UV1V9-nnaAs * Army: https://www.youtube.com/watch?v=G4DRBi66cOA https://www.youtube.com/watch?v=G4DRBi66cOA The USAF has a video because that's how planes used to do navigation outside of radio range—sextants on the ceiling of the cockpit: * https://www.youtube.com/watch?v=C7gAiI79nOY https://www.youtube.com/watch?v=C7gAiI79nOY * https://www.youtube.com/watch?v=xc3rAlCDf54 https://www.youtube.com/watch?v=xc3rAlCDf54

_yb2s 2y ago

It is not true- the authors sound very inexperienced with celestial navigation. There are many ways including the lunar distance method to get a position at night with regular equipment. The math is more complex than a simple noon solar sighting, but it can be done with just a regular cheap plastic sextant and a watch. It’s also no big deal to go 12 hours with no position. If you know your speed and heading you can accurately estimate your position much longer than that. Overall, they also made it sound almost impossibly difficult for a large team of professionals, when solo and otherwise short handed recreational sailors have been reliably sailing around the world with celestial navigation for more than a century- through all possible conditions.

danielvf 2y ago
Note that they were staying roughly 2 miles within the actual track, while having the bulk of the work being done by a combo of officers and newbs that they had just trained. That's high accuracy standards for celestial nav, not even counting that this is most of other people's first time doing this in anger.

quercusa 2y ago

And just how expensive is a bubble sextant?

wrycoder 2y ago
I have one I paid $150 for. But bubble sextants are usually only used on aircraft.
ianburrell 2y ago
I discovered that real Tamaya marine sextants are available on eBay for $100-150. They were 30x that new. My understanding is that the sextants are coming from breaker yards in India where the sextants were left on ships and salvaged.

throw0101a 2y ago

> Curious how navigation at night was not possible without expensive equipment, sounds like they were relying only on starts in the morning and evening? As a sibling comment notes, it is possible. There are tables for lunar distance: * https://thenauticalalmanac.com/Lunar_Distance_Tables.html https://thenauticalalmanac.com/Lunar_Distance_Tables.html * https://en.wikipedia.org/wiki/Lunar_distance_(navigation) https://en.wikipedia.org/wiki/Lunar_distance_(navigation) * https://www.starpath.com/resources2/brunner-lunars.pdf https://www.starpath.com/resources2/brunner-lunars.pdf The planets Venus, Mars, Jupiter, and Saturn can be used, as well as several dozen planets (lookup tables in an almanac) * https://en.wikipedia.org/wiki/Nautical_almanac https://en.wikipedia.org/wiki/Nautical_almanac * https://thenauticalalmanac.com https://thenauticalalmanac.com Two US military videos explaining the theory (ground points/GP, circle of position, etc): * USAF: https://www.youtube.com/watch?v=UV1V9-nnaAs https://www.youtube.com/watch?v=UV1V9-nnaAs * Army: https://www.youtube.com/watch?v=G4DRBi66cOA https://www.youtube.com/watch?v=G4DRBi66cOA The USAF has a video because that's how planes used to do navigation outside of radio range—sextants on the ceiling of the cockpit: * https://www.youtube.com/watch?v=C7gAiI79nOY https://www.youtube.com/watch?v=C7gAiI79nOY * https://www.youtube.com/watch?v=xc3rAlCDf54 https://www.youtube.com/watch?v=xc3rAlCDf54