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: Angular Distance Between Stars
    From: Greg Rudzinski
    Date: 2012 Sep 15, 12:04 -0700

    Frank,

    When using the William's GC calculator I'm getting quite a spread of results depending on the spheroid setting. What should be entered for the radius and flattening ratio to get correct star to star distances. My first effort measuring between Vega and Deneb was 5' out so something is very wrong here :(

    Greg

    [NavList] Re: Angular Distance Between Stars
    From: Frank Reed
    Date: 14 Sep 2012 09:45
    You can use any great circle distance calculator that allows you to enter latitude and longitude. Here's one:
    http://williams.best.vwh.net/gccalc.htm
    (for "Earth model", select spherical). Since this is a javascript calculator, you can view the source and modify it to suit your needs if you feel like messing around in code. Just enter SHA (or GHA) for longitude and Dec for latitude.

    Great circle distance doesn't depend on the coordinate system, so you could also enter azimuths and altitudes instead of SHAs and declinations. This is handy if you want the refracted distance. If you use a standard planetarium software app like Stellarium, you can set it for some location and time and read out the altitudes either true or refracted and then enter them into any great circle distance calculator.

    I've said this recently so I apologize for repeating, but you can get the refracted distance for any pair of stars when both altitudes are above 45 degrees to a good approximation by decreasing the true great cirlce distance by 1/3000 (a tenth of a minute of arc for every 5 degrees of distance).

    -FER


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