NavList:

David, you wrote:
"In addition, he must have had some way of knowing the Sun’s declination, or he couldn’t have worked out meridian passage latitudes. He only needed the declination at local noon, so if he knew the declination for that day and the next at Greenwich and his approximate longitude, he could work that out, so he could manage with a very small table of declinations for several years ahead such as appears in some almanacs."

Right, and assuming he had a copy of Moore's Navigator, this would have been the obvious source. Tables with four years worth of the Sun's declination were included in Moore and many other navigation manuals and "common" almanacs with the usual leap year instructions for advancing the tables ahead into later years. So even a copy of Moore from eight or ten years before the voyage would have provided the necessary data. The procedure for interpolating the declination based on the approximate local time and the approximate longitude was well-known, standard, and sufficiently accurate. No problems here. He knew the Sun's declination.

You added that Richard Dunn and Rebekah note in "Finding Longitude" that Bligh and company also had the "Tables Requisite" and "they also say that he had a sextant by Jesse Ramsden". As I noted in my short review back in the winter, that's an excellent book. I have only browsed it however, and I guess I missed that section. But fair enough then! They had at least two sextants aboard Bounty (or was it three?), so it would not have been any loss to give one to Bligh. But here's the thing: this would not have helped in any significant way. Neither the Tables Requisite nor a fine sextant would have provided them anything useful except, presumably, better morale. A wooden octant/quadrant, assuming it was a reflecting instrument, which I assume it must have been, was like a modern plastic sextant, yielding altitudes accurate to +/- 3 to 5 minutes of arc. That fine Ramsden sextant would be limited by the usual horizon accuracy so its altitudes would have been accurate to +/- 0.5 minutes of arc at best. There was no point in the open boat voyage where knowing the latitude to half a mile would have been more useful than knowing the latitude to within five miles. Unless they were trying to spot a low atoll, which somehow had a dead-on accurate latitude in 1789, they would have had no trouble reaching any chosen destination's latitude with either instrument. And since Moore himself had copied most of his tables from the Tables Requisite, leaving out only those that were counted as exotic or rarely used, I can't imagine that there was any real benefit from having the T. Reqs. (not to be confused with a T. rex, which is not a good thing to transport in a small boat).

The key datum that was missing, and I would argue was carefully prohibited by Fletcher Christian, was longitude. Without accurate longitude, Bligh should have stopped on some safe island and waited for rescue, possibly years later. The mutineers kept the chronometer from Bligh, and they also kept the Nautical Almanac, which made lunars for longitude impossible --and Christian knew this very well. There was no alternative. Tables of lunar distances were not included in other navigation manuals, like Moore. The mutineers would have benefited tremendously from the time that Bligh would have spent trapped in the western Pacific. They surely did not expect him to make it back to civilization (such as Timor was) so quickly.

You also wrote:
"A statement similar to this appears in Jules Vernes 'The Mutineers of the Bounty' 1879 when Christian says '[I] Also, give him my nautical charts, and my own sextant', but but did Verne's just expand on Belcher, and did Belcher copy from Morrison?"

Fascinating. I've never opened Verne's 'Mutineers'. Is it a good read?

You added:
"David Barrie says in 'Sextant' Ch4 'Equiped only with a sextant and a compass', and in Ch 4 reference 3 he says 'Bligh claimed in his published account of the voyage that he was allowed to take only a quadrant, but his journal shows that he actually had a sextant and navigational books' "

I was convinced already by Dunn and Higgit as sources. David Barrie, I found, had a tendency to repeat material from secondary sources. In any case, as I have described above, this is inconsequential. It's interesting trivia, but it does not make the navigation during the open boat voyage any easier, nor does it change the practice in any meaningful way. A sextant would not have helped.

Here's a hypothetical to ponder. Suppose Bligh had been presented with two options for celestial navigation (in addition to the compass, tables of latitudes and longitudes, and other elements of dead reckoning navigation):

• You can have this old wooden quadrant, that hasn't been adjusted in months, along with the Nautical Almanac and Astronomical Ephemeris for the current year, and also Moore's Navigator.
• Or you can have this beautiful sextant, Moore's Navigator, and every other book we have except the Nautical Almanac for the current year.

With the first option selected, which sounds worse, a navigator could get very good, completely sufficient latitudes and also usable longitudes by lunars (within a couple of degrees after careful averaging). With the second option, a navigator could get excellent latitudes, more accurate than necessary given the poor charting of the western Pacific, but no astronomical longitudes whatsoever.

Frank Reed