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: Moonrise video
    From: Greg Rudzinski
    Date: 2013 Apr 28, 18:31 -0700


    You say:

    "Excellent . However , I do NOT fly with you to Howland , especially if for an assessment of our position you refer to the rising sun , like mr.Noonan possibly did when nearing the island in 1937 ."

    An aviation navigator such as Fred Noonan would not have used a very low altitude observation of the Sun for determining a line of position. A line of position at the moment of sunrise was most certainly not used. A standard line of position using an azimuth and intercept was used from a pre-calculation done the day before so that an immediate line of position could be put down on the chart. Even an ancient mariner would not have used a very low altitude observation or sunrise sunset except in an emergency lifeboat situation.

    Greg Rudzinski

    Re: Moonrise video
    From: h.a.c. van Asten
    Date: 2013 Apr 28, 06:18 -0700
    Appreciated Opponent ,

    I refer to your link to the TIGHAR forum , where you pin a sunrise local hour angle miscalculation on me , with the remark that I should not necessarily demonstrate how to compute such angle , since navigators (your words : "who do understand celestial navigation")know how to do that themselves with their almanacs . For 150 SM off Howland westwards your algorithm for the hour angle of the sun at sunrise U.L. ends up at 87-45.7 , U.L. in the local horizon ,sea level , time 1754:53 GMT , which is all good . Excellent . However , I do NOT fly with you to Howland , especially if for an assessment of our position you refer to the rising sun , like mr.Noonan possibly did when nearing the island in 1937 .
    If you observe sun´s upper limb in the horizon by no matter what medium , the marine sextant , binoculars , or the unarmed eye , you do not look at the mean sun . You look at the true , apparent sun which on July 2nd is 3m50s slow on the mean sun for the 1700-1800 GMT time window . Your comparison Lapook-to- Asten local hour angle , 87-45.7 versus 88-43.2 accounts for 0-57´.5 . Multiply by 15 deg/hr and find 3m50s time point difference , exactly covering the equation of time since the sun´s rising time was 3m50s identically for 13.8 arcmin velocity per minute of time (*) . From any western point on the 500 SM radius about Howland-chart circle our distance made good is (1754:53 - 1540:00) x 150 MPH = 337 SM . However , the distance to our precomputed sun-up coordinates is 348 SM : we are 11 miles short and not 150 , but 161(**) miles off destination . Proceeding for the offset lane and turn-off point by DR (***) will bring us on a 157-337 position line 3m50s x 150 MPH = 9.6 miles westwards of Howland-chart , 14.6 miles westwards of Howland-true .
    We wil not run the destination in sight , head-on on our APL , since when passing at ETA over its latitude the island is 14.6 miles , 23.5 km on the port bow .
    . Therefore , not to offend you , I stay home and let you travel alone , for which the reason is that you did not follow the advise : If you observe sunset by the bubble sextant (true , apparent sun´s centre in the horizon) , KEEP TO THE BUBBLE SEXTANT for next morning sunrise but if not , you artificially shorten your night time window and as a result you undershoot destination . Mr. Noonan should have waited for (1754:53 + 3m50s) GMT = 1758:43 GMT to plot his DR offset for Howland . The mechanism is dealt with in EJN-July 2008 , p.27 , figures 3 & 4 .

    Eventually , you disqualify my on the subject articles series by stating that they are littered with errors , thereby bringing into discussion the theory´s consistency . It is true that for the relevance there is up to now no proof , but no complaint about consistency , the articles having been meanwhile gone through by many readers the world over , has been brought to my attention ,

    sincerely yours ,

    H.A.C.van Asten

    (*) Vr/min = 15´sin 67 . cos 00-09
    (**) R.Con.Nesbit in Aeroplane Monthly , Feb. 1989 , p.71 ,without further calculation , gives "approximately 160 miles off" , at sunrise .
    (***) P.Mantz remembering F.Noonan´s "Find the Island" fashion (Mantz biography ´Hollywood Pilot´ , interview) .

    It may for members of this forum be of interest to solve for the sunrise time-distance-coordinates group from sunset the evening before . It can be made for any pair of locations , here executed for the Earhart New Guinea to Howland flight , July 2 , 1937 , departure 0000 GMT from Lae . Sunset 159-07-E / 04-33.5-S . Sunrise next morning 150 SM off Howland-chart . For one single day you can delete the Equation of Time difference and work with apparent time .

    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

    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