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
    9 Degrees of Frost
    From: Brad Morris
    Date: 2013 Jan 24, 19:42 -0800

    Today, I set out to measure a sun-moon lunar distance of 153 degrees 42 minutes.

    First, the weather. In the words of Shackleton, "9 degrees of frost". In our world, 23 degrees F. Brrr. Wind gusting out of the north up to 24 knots. Wind chill temp, 8 degrees F. Double Brrr.

    I was all set though, my parka is a Canadian Goose Expedition model, advertised to be precisely the same model as used at McMurdro and at the South Pole Station. My hands were protected by Alti Mitts, advertised for summiting at Everest. So I was super warm!

    I arrived at 3:25 PM and immediately set the reflecting circle outside to acclimate to the temperature. I also set out my GPS, which has the ability to average readings. 2000+ averages later, my position was 40.8368666N 72.49521666W. This was verified against Maps, and showed to within 50 feet of my true position, using satellite imagery.

    By 3:45PM I reasoned that the metal of the reflecting circle had stabilized and I checked the index error. Unfortunately, manual dexterity with the super warm Alti Mitts was lacking, so off they came. Index A showed 0 d 0 m 0 s, Index B showed 0 d 2 m 20 seconds. Note that the reflecting circle has two indices, to guard against eccentricity error in the main journal. The second index is not independently adjustable. There are also two separate arcs! The indices were verified against the sun and against the horizon.

    I bravely set 153 Degrees 42 minutes on the arc using index A, and attempted to align the sun and moon. Try as I would like, I could get one but not the other. After 45 minutes of fiddling, I finally yanked out the scope to perform a mark one eye ball alignment. To my great surprise and utter embarrassment, the reflected image was the top of my head, not the other body. Dang! So I popped on the right angle eyepiece prism, so as to pull my head 90 degrees to the side. Here was a novel problem. I couldn't even get one body in the scope. One half hour later, the sun set. It was 5PM.

    I swiftly moved on to the Polaris backsight. First, I checked that I could see the horizon and the sky, with the circle set to 139 Deg 10 min. Success! On with the Alti Mitts. Next, I pulled out my Celestron SkyScout and told it to locate Polaris. Once I could see Polaris with the naked eye, I tried the backsight, naturally with the gloves off. It was 5:26. My hands just were too cold and wouldn't work any more. I abandoned the effort.

    Lessons Learned
    1) For long distance lunars, I'm going to need a tripod to hold the reflecting circle while I perform initial alignment of the telescope to body # 1. Then the right angle prism can go on. Finally, I can search for object #2 without my head in the way.
    2) The backsight, since it won't need the right angle prism, is more readily obtained. Its going to be interesting trying to swing the circle around the imaginary axis to the star!
    3) 9 degrees of frost was ccccold! How Shackleton endured 80 degrees of frost is beyond my (ahem) endurance! Pun fully intended. Hopefully this cold snap ends soon.

    Regards
    Brad
    ----------------------------------------------------------------
    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