Welcome to the NavList Message Boards.


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

Compose Your Message

Add Images & Files
    Name or NavList Code:
    Re: Position Angles (PA) angular rates
    From: Antoine Couëtte
    Date: 2023 Nov 18, 18:04 -0800

    This [lonesome] thread was initially triggered by Frank's "Alnair identification" quizz-thread in which Peter Blaskett made a very important contribution under the form of a quite instructive Picture showing in particular the South Pole above the horizon (left of the Picture), which fully makes sense here since the Observer's actual position is at S13°15.0'.

    Accordingly, since this previous hand-drawn sketch of mine assumed to be taylored to an Observer at an approximate 13°S Latitude incorrectly represents the South Pole well under the horizon, it does require edition / correction as it actually sketches a sky view applicable to some Northern Observer.

    In the enclosed attachment, I am bringing remedy to this through the following steps :

    (1) - On top of this updated attachment : simply renaming the early Al Nair & Peacock into Star A & Star B without changing the initial hand-drawn sketch.

    (2) -  At the bottom of this updated attachment : adding a complementary sketch better taylored to the actual Observer's Lat close to 13°S - hence with South Pole showing [slightly] above the horizon then - in which it is again possible to adequately name the relevant stars as AlNair and Peacock this time.

    It should noted that the initial Formula (1.2)  : dPA/dUT =  (sinAz*cosAz/tgP - sinLat*sin²Az) * dP/dUT does not require any modification since it is a general formula applicable to all configurations.

    (3) - Finally it is also an opportunity here to correct (into bold underlined characters this time) and re-edit a few typos in my previous post which should read :

    (3.1) - Start multiplying both sides by sin²Az, then divide both sides by sinP and get : dP * (sinAz * cosAz / tgP ) - dAz = dP * sinLat * sin²Az

    and :

    (3.2) - 2.1.4 - At UT = 05h59m00.0s

    Alnair Height/Azimuth = 33.10401°/221.95652° and Peacock Height/Azimuth = 15.99405° /214.31987°, PA=20.59411°


    Browse Files

    Drop Files


    What is NavList?

    Get a NavList ID Code

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

    A NavList ID Code guarantees your identity in NavList posts and allows faster posting of messages.

    Retrieve a NavList ID Code

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

    Email Settings

    NavList ID Code:

    Custom Index

    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