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
    Re: Having trouble
    From: Patrick Goold
    Date: 2012 Jan 10, 19:57 -0500
    Bill,
    Thanks for your thoughtful response to my query!  

    I am using a Tamaya MS-933, made in 1979.  It has the original scope.

    My beach sights are made at pre-dawn twilight at five feet above sea level.

    Would the 7x35 Prism telescope that Celestaire sells help distinguishing the sea horizon as well as possibly sharpening the stars?

    Best regards,
    Patrick


    On Mon, Jan 9, 2012 at 3:43 AM, Bill Morris <engineer@clear.net.nz> wrote:

    Patrick

    Start by getting comfortable. Sit down and have the A/H at a suitable height for the shot you're taking, higher for low angle shots and vice-versa. It may even help to rig up some sort of adapter, say a small hobby vice, so that you can mount the sextant on a tripod while you get your technique sorted out.

    You don't say which sextant you are using, nor which telescope. Some telescopes have very restricted fields of view, which can make finding a star in the sky difficult, never mind matching it with the correct one in the A/H. You could perhaps start without a telescope, to get coincidence and then attach the scope, rock the sextant to pick up the reflection and get exact coincidence. You can make things ten times more difficult for yourself by using an inverting 'scope and much easier by using a prismatic monocular, as it has a wide bright errect field of view.

    I used to practice using the surface of a swimming pool on quiet nights in between breezes, so if you have access to a private one, you could gain some confidence using that.

    As for the splattered stars, all three of the things you have mentioned could be responsible, but the telescope is perhaps the most likely culprit, not forgetting that things like myopia, astigmatism and even quite small central cataracts in you eyes can degrade a point image. If stars are not splattered when you use a liquid horizon, you can of course blame the mirror, but otherwise, I would look to the cleanliness of the telescope lenses and the general quality of the telescope. It is fairly important to try to get the image as central as possible in the field of view.

    When you write about the natural horizon, I assume you are referring to it in daytime, or perhaps at dawn twilight. While the higher magnification of a prismatic monocular can help in decding where the horizon lies, you can also try getting lower down, so that your horizon is much closer. The chances of getting a good horizon are much diminished if you are at 200 metres above sea level compared, say to 5 metres or less.

    Bill Morris
    Pukenui
    New Zealand


    ----------------------------------------------------------------
    NavList message boards and member settings: www.fer3.com/NavList
    Members may optionally receive posts by email.
    To cancel email delivery, send a message to NoMail[at]fer3.com
    ----------------------------------------------------------------




    --
    Dr. Patrick Goold
    Department of Philosophy
    Virginia Wesleyan College
    Norfolk, VA 23502
    757 455 3357


       
    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