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: Radium illumination
    From: Gary LaPook
    Date: 2010 Sep 07, 19:35 -0700

      Thanks for all the suggestions. I have decided to just leave the A-7
    alone since I have other sextants to use at night and the A-7 works
    really well and I don't want to disassemble it and possibly screw up a
    good thing.
    But since you guys have scared me about the radiation exposure I decided
    to cover the sextant with lead scuba diving weights and lead shot. The
    lead is a little more than 4 inches thick which equals two, one-tenth
    thicknesses. This will attenuate the radiation by a factor of one
    hundred so instead of the 1.6 millirems exposure per year without the
    lead it should only be 16 microrems which is well below the 200
    millirems normal background exposure and only about 1/300,000th of the 5
    rems per year exposure allowed under OSHA regs.
    On 9/7/2010 12:49 AM, Frank Reed wrote:
    > Gary, you wrote:
    > " Twelve hours later the most sensitive dosimeter registered 70
    > milliroentgens which was confirmed by the second dosimeter showing
    > something less than a tenth of a roentgen and the least sensitive
    > dosimeter registered no change.This means that the rate is about 6
    > milliroentgens per hour which would result in an exposure of about 50
    > roentgens per year, about 250 times the normal background exposure!
    > Any exposure below 25 rems (approximately the same as a roentgen)
    > produces no detectable clinical effects on humans so one could spend
    > six months inside the sextant box without harm."
    > That's very close to my experience with a nice old mechanical alarm
    > clock that I've been carrying around since I was about ten. The clock
    > was nearly new when I found it, and I would guess by the style that it
    > was probably manufactured in the 1960s. It's a common Westclox "Baby
    > Ben". I discovered, when I was about twelve, one dark night with a
    > telescope eyepiece used backwards that the hands looked like a swarm
    > of thousands of fireflies when magnified. The scintillation was, and
    > is, just beautiful. I just checked, and it's still sparkling away...
    > Way back then, I was somewhat surprised to discover that other
    > "glow-in-the-dark" clocks and toys were much less interesting when
    > magnified --no fireflies. Years later, sometime around 1990, I
    > acquired a little radiation monitor that connects to a PC serial port
    > (it's very entertaining and I still experiment with it now and then.
    > If anyone wants one, the home-business selling this particular item is
    > still around. It's Aware Electronics, and the model of radiation
    > monitor that I have is the "RM-60". If you don't have a computer with
    > a serial port, you'll need an adapter. See his web site). When exposed
    > to the old alarm clock, the radiation monitor's software spikes right
    > through the roof, and it's software geiger counter, normally clicking
    > quietly, becomes a continuous buzzing sound. It's amazing to see and
    > hear. Various rocks and other objects also show higher than normal
    > radiation levels. It's also interesting to see the radiation levels
    > climb during airline flights --at 30,000 feet you're above most of the
    > atmosphere so radiation exposure is about 20-30 times higher than
    > normal sea level background radiation. In fact, the correlation is so
    > good that the radiation count makes a decent altimeter.
    > Again, the paint on the hands of my alarm clock is scintillating RIGHT
    > NOW. I presume that these "hot" clocks turn up on ebay regularly. Buy
    > a few. Scrape the paint off the clock's hands and grind it up (being
    > VERY CAREFUL not to inhale the dust) and mix with fresh paint. Apply
    > to sextant. Would that work?
    > -FER
    > PS: I also used to assemble nuclear weapons... but only as a hobbyist. :o
    > ----------------------------------------------------------------
    > 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