Brandis Sextant Taxonomy, Part Seven: Outlier Sextants

Several Brandis sextants I’ve come across aren’t like of any of the five sextant types I’ve discussed in previous posts.  One of these outliers is a sextant with Brandis serial number 5687 (Figure 1).  Brandis 5687’s frame has one straight and one curved lateral brace connecting its radial arms, like the U.S. Navy Surveying Sextant illustrated in Brandis Catalog No. 20 (Figure 2).  Because of its frame pattern, I initially thought that Brandis 5687 was a surveying sextant but then I noticed that its arc scale is graduated in 10-minute intervals (Figure 3).  U.S. Navy surveying sextant specifications published in 1897, 1901, and 1918 require the arc scales of surveying sextants made for the Navy to be graduated in 20-minute intervals, so Brandis 5687 isn’t a surveying sextant, at least not according to these specifications.

Figure 1.  Brandis 5687

Figure 2. Brandis Catalog No. 20

Figure 3.  Brandis 5687's Arc Scale

Brandis 5687 was the first sextant of its type that I came upon, but eventually I found two more like it; their Brandis serial numbers are 5965 and 6028, respectively.  I came upon all three of these sextants on eBay, and so all I know about them is what I can see in the photos posted in their eBay listings and what little their sellers had to say about them.  As far as I can tell, none of these sextants are marked with a Naval Observatory serial number but it may be that the photos provided in their eBay listings don’t happen to show them.  I’ll note here that the eBay listing for Brandis 5965 reported its box to have dimensions of 10” x 10” x 5.5”, which matches the dimensions of Brandis surveying sextant boxes.  That tells me that sextants of this type have the same frame radius, 6 inches, as a Brandis surveying sextant.

The U.S. Navy’s high grade sextant specifications published in 1897 requires the arc scales of high grade sextants to be graduated in 10-minute intervals. Brandis 5687 meets this requirement, but it fails to meet an additional requirement in these specifications that high grade sextants have at least two curved lateral braces connecting their radial arms. The frame pattern of Brandis 2864 (Figure 4), which was discussed in my earlier post on Brandis high grade sextants, conforms with this specification as does the frame pattern of the high grade sextant illustrated in Brandis Catalog No. 20 (Figure 2).

Figure 4. Brandis 2864

So far we’ve looked at how Brandis 5687’s frame and arc scale compare to those of Brandis surveying sextant and high grade sextants. Let’s next look at how Brandis 5687’s tangent screw compares to the tangent screws that sextants of these two types are fitted with.  The U.S. Navy’s surveying sextant specifications published in 1901 requires surveying sextants to have a 2.75-inch long, two-headed tangent screw, while the Navy’s specifications for high grade sextants published in 1897 requires high grade sextants to have a 4.1-inch long, single-headed tangent screw.  The surveying and high grade sextants illustrated in Brandis Catalog No. 20 (Figure 5) appear to be fitted with the tangent screws called for in these specifications, so it seems that the Navy sextant specifications in effect when Brandis Catalog No. 20 was published called for the same kind of tangent screws that the earlier specifications did.  What kind of tangent screw is Brandis 5687 fitted with? The photo in Figure 1 shows us that it has a short, two-headed tangent screw. Photos I have of Brandis 5965 and Brandis 6028 show that they too, are fitted with a short, two-headed tangent screw.

Figure 5  Tangent Screws, Brandis Catalog No. 20

As a final point of comparison, let’s consider how Brandis 5687’s sighting devices compare to those of Brandis surveying and high grade sextants.  Both the U.S. Navy’s surveying sextant specifications published in 1901 and its high grade sextant specifications published in 1897 require instrument manufacturers to furnish these sextants with a sighting tube, short telescope, and long telescope.  These three devices can be seen in the illustration of the surveying in Brandis Catalog No. 20.  They also can be seen in the illustration of the high grade sextant in Brandis Catalog No. 20, but an additional device appears in this illustration as well.  That additional device is a second eyepiece for the high grade sextant’s long telescope.  The Navy’s 1901 surveying sextant specifications requires a surveying sextant’s long telescope to be furnished with an eyepiece providing a magnification of six diameters, while the Navy’s 1897 high grade sextant specifications require the long telescope of a high grade sextant to be furnished with two eyepieces providing magnifications of six and twelve diameters, respectively. Apparently, the sextant specifications in effect when Brandis Catalog No. 20 was published were the same as these earlier specifications with respect to the sighting devices these two sextant types were to be provided with.  A photo of the sighting tube, short telescope, long telescope, and second eyepiece for the long telescope of a high grade sextant, in this case the high grade sextant Brandis 2864, can be seen in Figure 6.  The way these four devices are stored in Brandis 2864’s box can be seen in Figure 7.  The holder for the long telescope is at the bottom right of the box, while the holder for the sighting tube, short telescope, and long telescope is at the box’s rear right corner.  In the photo in Figure 8 of Brandis 5687 in its box, a sighting tube, short telescope and long telescope, can be seen but not a second eyepiece for the long telescope.  We can be sure that the photographer didn’t neglect to include a second eyepiece in this photo, because this photo shows that the holder in the corner of Brandis 5687’s box doesn't have a space to hold such a thing.  So Brandis 5687’s long telescope has only one eyepiece, and in this respect Brandis 5687 is like a surveying sextant. Photos that I have of Brandis 5965 and Brandis 6028 show that their long telescopes, too, were supplied with only one eyepiece.

                                                     Figure 6. Brandis 2864 Sighting Devices (l to r):                                                                    Second Eyepiece for Long Telescope, Sighting Tube, Short Telescope, Long Telescope.

Figure 7.  Brandis 2864 Box with Sighting Devices in their Holders

Figure 8. Brandis 5687 in its Box, with Sighting Devices

Brandis 5687 and other sextants of its type are like Brandis surveying sextants in terms of their frame pattern, tangent screw, and the sighting devices with which they were provided, but their arc scales are graduated like the arc scales of Brandis high grade sextants. Sextants like Brandis 5687 don’t appear in any Brandis product literature I’ve seen and so I don’t know what name Brandis had for them  Until I have a better idea what sextants like Brandis 5687 were called, I’ll refer to them as ‘Type 6 sextants’, simply because they are the sixth type of sextant I’ve discussed.

A photo of second type of outlier sextant that I’ve come across appears in Figure 9.  Its Brandis serial number is 5981 and it is also marked with U.S. Naval Observatory serial number 1142.  What sets Brandis 5981 apart from the sextants discussed in previous posts is that its frame has three curved lateral braces connecting its radial arms.  Brandis 5981’s arc scale is marked in 10-minute increments, like the arc scale of a high grade sextant.  Brandis 5981’s frame pattern is different than the high grade sextant depicted in Brandis Catalog No. 20, but it nevertheless conforms with the U.S. Navy’s 1897 high grade sextant specifications, which requires high grade sextant frames to have at least two lateral braces.  Brandis 5981’s tangent screw is long and single-headed as required by these specifications, and its long telescope has two eyepieces, which also meets the requirements in these specifications.

Figure 9 Brandis 5981

As was the case for the Type 6 sextants, I don’t have any Brandis product literature that indicates the name Brandis had for sextants of this type. A partial scrap of the U.S. Naval Observatory inspection certificate inside the lid of Brandis 5981's box is not legible in the photo I have of it, which is unfortunate, because that certificate might have told us what the U.S. Navy called sextants like it [1].  Until I find something that tells me what sextants like Brandis 5981 were called, I’ll unimaginatively refer to them as Type 7 sextants.

Brandis 5981 isn’t the only Type 7 sextant I’ve come across.  Another sextant of this type has Brandis serial number 5851 and is marked with U.S. Naval Observatory number 1110.  Brandis 5981 and Brandis 5851 have some of the highest Brandis serial numbers I’ve seen, yet their Naval Observatory serial numbers are lower than most Brandis sextants I’ve seen.  That is something that is worth further discussion, but I’ll save that discussion for some future post.

Once I became aware of the existence of Type 7 sextants I realized that I’d seen a photo of a Brandis sextant frame with three curved lateral braces in Bill Morris’s book, The Nautical Sextant.  The frame, separated from the rest of the sextant, appears on a page comparing the similarly detached frames of sextants from several different manufacturers.  I contacted Mr. Morris to learn more about this sextant, thinking it was another Type 7 sextant.  What he told me about this sextant, whose Brandis serial number 5191, suggests that it is yet another type of Brandis sextant.  Mr. Morris reports that Brandis 5191’s vernier scale is graduated to provide a 30-second reading precision.  As we’ve seen, the arc scales of Type 7 sextants are graduated in 10-minute intervals.  In my experience looking at Brandis and other sextants, I’ve pretty consistently found that sextants with vernier scales providing a 10-second reading precision have arc scales graduated in 10-minute intervals, and sextants with vernier scales providing a 30-minute reading precision have arc scales graduated in 20-minute intervals.  The U.S. Navy sextant specifications referred to earlier in this post in fact require these particular pairings of vernier scale reading precisions with arc scale graduations. The 1901 surveying sextant specifications require an arc scale graduated in 20-minute intervals and a vernier scale providing a 30-second reading precision, while the 1897 high grade sextant specifications required an arc scale graduated in 10-minute intervals and a vernier scale providing a 10-second reading precision.  The 30-second reading precision of Brandis 5191’s vernier scale suggests to me that Brandis 5191’s arc scale is graduated in 20-minute intervals, and so I’m tentatively taking Brandis 5191 to be an example of yet another Brandis sextant type, which I will refer to as a Type 8 sextant.  I will reach out to Mr. Morris and ask him specifically how Brandis 5191’s arc sale is graduated and what kind of tangent screw it is fitted with.  As of this post’s publication date, I’ve seen no other sextant like Brandis 5191, so it is an outlier even among the outlier Brandis sextant types discussed in this post.

This was a difficult post to write.  I didn’t report every bit of information that I have about these different sextant types or fully flesh out my assumptions because to do so would have required digressions that I felt were too lengthy.  Classifying these outlier sextants as belonging to three types distinctly different from each other and from the sextant types discussed in earlier posts was a useful way to organize my discussion of them, but it may not be the way people classified them back when Brandis was making them.  For instance, it could be that what I’ve categorized as a Type 7 sextant was simply a later, beefed-up version of the U.S. Navy High Grade sextant featured in Brandis Catalog No. 20.  If and when any new information comes in about any of these outlier sextant types that helps to better understand them, I will update this post or write a post to update what appears here.

Comments, corrections, additional relevant facts, differing viewpoints, etc., are always welcome.  Send to gardnersghost@gmail.com
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Footnote
[1]  Naval Observatory inspection certificates have a line where the sextant’s type was usually, but not always, been entered.