Welcome to the NavList Message Boards.

NavList:

A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Message:αβγ
Message:abc
Add Images & Files
    or...
       
    Reply
    F. Barker & Son Box Sextant
    From: Sean C
    Date: 2016 Apr 6, 13:07 -0700

    I received my box sextant yesterday. (It took only one week to travel from Telford, Shropshire, England to Newport News, VA, USA!) I must say: I think I did indeed get lucky with this purchase. The sextant is in very good condition - exactly as pictured in the eBay listing. The leather case is also in very good condition. Both show only minor wear.

    Upon un-boxing it, I immediately noticed a rattling sound. Removing the cover revealed that one of the square-headed side error adjusting screws had come loose during shipping and had completely fallen out. Thankfully, it was easily reinstalled with the adjusting tool and now seems to be working perfectly. After a brief inspection, I set the index arm to zero and stepped outside to check the index and side error. I was surprised at just how tiny the scale markings are. Even with the magnifying lens, they were dificult to read under my kitchen light. Once outside, being in the middle of the night, I found that Jupiter was the most convenient body available at the time. It was then that I discovered a strange distortion in the double reflected image: it seemed to be 'smeared' at about a 45 degree angle. (See the attached picture of a simulated view through the scope.) Removing the telescope and sliding the peep hole into place provided what seemed to be a sharper reflected image. The condition of the horizon glass is such that it absorbs enough light to make even bright stars barely visible.

    Back inside, I inspected the filters more closely. The detachable telescope filter appears to be dark green in color. Looking through it is comparable to looking through both of the middle index shades on an Astra IIIb. One of the box sextant's index shades is orange in color, similar to the orange plastic that comes with the Davis artificial horizon, but darker. The other is green and is similar to one of the middle index shades on the Astra. When used together, they dim the light about as much as the darker of the two outer index shades on the Astra.

    Today, I decided to use my Davis artificial horizon to try some sun sights. Before taking the sights, I used the sun to check the index and side error again. The double reflected sun also appeared slightly distorted, although it wasn't as obvious as Jupiter's distortion. The sun just looked slightly oval in shape - again, stretched along an axis of about 45 degrees. It wasn't too bright through the telescope filter, but I'd prefer it to be a little darker. I had a bit of difficulty finding the sun in the mirrors, but eventually got a couple of sights before it got too high to use with the A.H. Due to the distortion, I chose to overlap the images instead of bringing the limbs together. Here are the results:

    __UT______Hs (A.H.)____/2_______R_______Ho________Hc______error

    15:53:04___110°29'___55°14.5'___-0.7'___55°13.8'___55°14.0'___-0.2'

    15:57:20___111°24'___55°42.0'___-0.7'___55°41.3'___55°42.1'___-0.8'

    Needless to say, I was quite happy with the results. :)

    Also attached is half of a business card that was in the case with the sextant.

    Cheers,

    Sean C.



    File:



    File:



       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Join NavList

    Name:
    (please, no nicknames or handles)
    Email:
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.
    Email:

    Email Settings

    Posting Code:

    Custom Index

    Subject:
    Author:
    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site