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-   -   Navigation instrument?? (https://www.trawlerforum.com/forums/s36/navigation-instrument-48330.html)

jimisbell 12-29-2019 05:20 PM

Navigation instrument??
 
I have what looks like a sextant made by Charles Escher (the weird artist).

It has two scopes looking in opposite directions, both with variable density sun shields. The central mirror can be controlled from either side.

My first impression was that it was made to shoot Lunars or just to measure the angle between two objects. But that can be done with only ONE scope.

The odd thing is that both scopes use the SAME central mirror but it can be controlled by either side so independent measurements are not possible. Just one at a time.

My next guess is that is is an incorrectly interpreted copy of an old instrument that actualy allowed two separate measurements to be made at the same time.

So what is this instrument and how is it used. Any one REALLY know?

High Wire 12-29-2019 05:22 PM

How about a picture?

jimisbell 12-29-2019 05:48 PM

I would if I could but when I try to send the pictures from my phone to my computer I get an "error: uploading media"

Just imagine a sextant with a full 360 arc, a circle that can be held either side up with a
120 degree scale and vernier on opposite sides, BOTH connected to the central mirror.

GregBrannon 12-29-2019 06:05 PM

You can take classes, and I recommend taking them in person with someone recommended as an instructor in the topic. Using the results to approximate one's position requires digging numbers out of references and then some math. It's not complex math, but it's easy to make mistakes and end up with poor answers. I successfully completed the course many years ago and never thought about doing it again or using what I'd learned - ever, so I can't recommend a source of instruction, but someone else here probably can.

Greg.

jimisbell 12-29-2019 06:09 PM

https://www.superbrass.com/users/good...ndsextant1.jpg

jimisbell 12-29-2019 06:14 PM

Quote:

Originally Posted by GregBrannon (Post 832763)
You can take classes, and I recommend taking them in person with someone recommended as an instructor in the topic. Using the results to approximate one's position requires digging numbers out of references and then some math. It's not complex math, but it's easy to make mistakes and end up with poor answers. I successfully completed the course many years ago and never thought about doing it again or using what I'd learned - ever, so I can't recommend a source of instruction, but someone else here probably can.

Greg.

I know how to use a sextant. THIS IS NOT a sextant. The picture I posted came from the internet its not mine. But there were no instructions on how it is used.

jimisbell 12-29-2019 06:43 PM

I have found that they are used as a Sextant is but they improve accuracy by doubling the angle. That is after a sight is made, the angle is measured on BOTH scales and are averaged. This is supposed to minimize the man made errors in the engraving of the scale. So far research leads me to believe that while these worked they did not make a big improvement.
Still dont see the need fr two scopes. The angle doubling is a mechanical thing that does not require a second sight.

twistedtree 12-30-2019 07:14 AM

Just looking at it, could it be used by two people to measure the angle (difference in bearing) between two sighted objects? Say the difference between the bearing to a lighthouse and a point of land? Those bearings are how we used to locate ourselves, and perhaps this device is a more accurate version of the same thing?

twistedtree 12-30-2019 07:18 AM

I think "Charles Escher" is different from the artist who was MC Escher, or Maurits Cornelis Escher

psneeld 12-30-2019 07:21 AM

I thought I remember one on an old USCG buoy tender..... used for triangulation placement of buoys before more modern equipment and techniques replaced it

twistedtree 12-30-2019 08:29 AM

Quote:

Originally Posted by psneeld (Post 832860)
I thought I remember one on an old USCG buoy tender..... used for triangulation placement of buoys before more modern equipment and techniques replaced it


That would make a lot of sense.


Also, I wonder if "Charles Escher" could be an engraving of the owner's name, rather than the manufacturer? Although if it was a CG device, it wouldn't have been owned by an individual. Anyway, it's a possibility worth considering.


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