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: Right Ascension.
    From: Bruce Stark
    Date: 2005 Aug 26, 20:49 EDT
    Right ascension is the order in which the sun, moon, planets, and stars "ascend" to the celestial meridian. "Right" was used here to mean "correct" or "true," as when a straight line was called a "right line." That's my notion, anyway.

    If you know the RAs of ten or twelve stars, separated from each other by two hours or so, and are familiar with the sky around them, you'll have a pretty good idea what's overhead, day or night, any time of year. This can be handy if you're out under the night sky for the first time in months, and drifting clouds obscure parts of constellations, so that nothing you can see makes sense.

    The sun's RA is zero March 20, and increases about an hour every half-month. For instance, it's been about five months since March 20, so the sun's RA should be roughly ten hours. Adding the time SINCE YOUR LAST NOON to the sun's RA gives the RA of your meridian. Drop twenty-four hours, if it's more than that.

    It's about five PM here. Knocking off an hour for daylight time makes it four hours since noon. Adding the sun's RA tells me that the RA of this meridian is about fifteen hours. Arcturus, RA about fourteen and a quarter hours, and declination about nineteen and a quarter degrees north, should be overhead. About twenty-five degrees south of me and probably a little west of south. Can't see the star, since it's daylight, but it's there.

    Bruce
       
    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)