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
    Re: Compass correction using sunrise
    From: David Pike
    Date: 2022 Jun 28, 01:48 -0700

    Frank you wrote: That refraction quantity, 34', only applies to observers near sea level at standard temperature and pressure

    That’s especially true for aircraft.  I guess that as the horizon is farther away at altitude, the sunbeam must come through more atmosphere.  If you add on dip at altitude, the effect can be quite large.  I have read of Lancaster Rear Gunners experiencing two or three sunrises descending into base after an operation.  I took this with a pinch of salt, but looking at the attached photograph of Table 6 from AP3270 (HO249) Vol 3 (liberated from Vulcan XM603) you can see that at 20,000ft the Sun can be observed down to about -3.3 degrees Hs with a bubble sextant, or they wouldn’t have continued the column down to 2.3 degrees Ho.  It’s perfectly possible that descending rapidly at the appropriate time from 20,000ft they might see at least two sunrises.  DaveP


    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    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 Settings

    Posting 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