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: Camera FAR 2nd Ed.
    From: Greg Rudzinski
    Date: 2012 May 30, 07:31 -0700

    Marcel,

    It is not as complicated as you think. The reflected Sun image is a constant angle that repeats exactly and requires only one single calibration to determine and is transferable to any lens or camera unchanged or simply used without a camera and timed as if a sunset. The loss of precision is in finding the vertical to the horizon since the Sun isn't near the horizon to be rocked back and forth for the low point. There is in addition a loss of image sharpness from added glass reflections that disrupt the symmetry of the Sun's reflected image.

    Greg Rudzinski

    [NavList] Re: Camera FAR 2nd Ed.
    From: Marcel Tschudin
    Date: 30 May 2012 14:08
    Greg,

    Regarding the accuracy you attain with your various FAR systems: Could it be that the loss of accuracy results from an error in not considering or wrongly considering differential refraction? The calibration of your lens considers refraction between actual altitude and apparent horizon. The reflection of the Bris moves the image to an altitude where the original calibration (refraction) is no longer true. May be one can obtain a good approximation with the original curve by adding or subtracting the difference in refraction. Imagine the sun being at 50* altitude being refracted by Ref(50). This image is now shifted down by e.g. 28* 46' producing an image at 21* 14'. Your calibration curve considers refraction between this altitude and the apparent horizon, but not between 50* and the horizon. As a gross approximation you may try to correct this (by adding or subtracting ?) with the difference between Ref(50) and Ref(21* 14'). It is however my understanding that in order to do it correct requires to derive separate calibration curves for each of the two Bris images.

    Regards,
    Marcel

    ----------------------------------------------------------------
    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
    ----------------------------------------------------------------

       
    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