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
    Name or NavList Code:
    Email:
       
    Reply
    Re: It's Moon-landing Monday
    From: Brad Morris
    Date: 2009 Jul 24, 11:59 -0400

    I suspect that method would work, albeit a bit clumsy.  There will be a nasty 
    transformation for the vector described by the telescope to the direction 
    vector. This will be nasty simply because the window probably won't be 
    orthogonal AND the craft will probably be tumbling in all three angular 
    directions of roll, pitch and yaw simultaneously.  That would be the job of a 
    computer program and not hand driven reductions (Space Bygrave anyone?).  And 
    since it would be computer driven, there would be a corresponding hard mount 
    location for the telescope, certainly not the ubiquitous duct tape!
    
    
    
    -----Original Message-----
    From: NavList@fer3.com [mailto:NavList@fer3.com] On Behalf Of frankreed@HistoricalAtlas.com
    Sent: Friday, July 24, 2009 2:22 AM
    To: NavList@fer3.com
    Subject: [NavList 9206] Re: It's Moon-landing Monday
    
    
    Brad you wrote:
    "That would be an interesting exercise.  The sextant must therefore be aligned
    to the thrust axis of the vehicle.  In other words, holding your sextant in
    your hand and pointing it out the window (with the previously agreed exercise
    on distance, RA and declination of the center of your vehicle) does not
    really tell you how your vehicle is pointed!  Assuming that the roll of the
    vehicle doesn't matter, then the vehicular pitch and yaw will not be known
    UNLESS the sextant is referenced to the vehicle.  I am not sure how we do
    that with our high end marine sextant!"
    
    How about this: take the telescope off the sextant and tape it to a window 
    (with duct tape, always assumed to be available) so that the end of the 
    telescope is flush against the glass. Now put the spacecraft in a slow roll 
    about the axis of thrust for the main engine. We can assume that this can be 
    done. Now you fire up your star chart software on your laptop and plot the 
    stars that you see while you look through the telescope during one roll. 
    Those stars will lie along a circle (probably not a great circle) on the 
    celestial sphere, and the center of that circle is the direction in which 
    you're oriented. When you fire your rocket, you will need to maintain that 
    orientation, so you have to fire the thrusters occasionally while you look 
    through the telescope maintaining whatever stars you see centered in the 
    field of view.
    
    On the Apollo missions, there was a sextant built into the spacecraft but it 
    was rarely used as a sextant is intended to be used --to measure angles 
    between objects. Instead it was used to get spacecraft orientation (since it 
    was built in, it was aligned to the spacecraft axes in a known way), and it 
    was used as a telescope to observe the lunar surface.
    
    -FER
    
    
    
    
    
    
    "Confidentiality and Privilege Notice
    The information transmitted by this electronic mail (and any attachments) is 
    being sent by or on behalf of Tactronics; it is intended for the exclusive 
    use of the addressee named above and may constitute information that is 
    privileged or confidential or otherwise legally exempt from disclosure. If 
    you are not the addressee or an employee or agent responsible for delivering 
    this message to same, you are not authorized to retain, read, copy or 
    disseminate this electronic mail (or any attachments) or any part thereof. If 
    you have received this electronic mail (and any attachments) in error, please 
    call us immediately and send written confirmation that same has been deleted 
    from your system. Thank you."
    
    --~--~---------~--~----~------------~-------~--~----~
    NavList message boards: www.fer3.com/arc
    Or post by email to: NavList@fer3.com
    To , email NavList-@fer3.com
    -~----------~----~----~----~------~----~------~--~---
    
    

       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Get a NavList ID Code

    Name:
    (please, no nicknames or handles)
    Email:
    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:

    Email Settings

    NavList ID 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