NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Interesting ebay find: Plath suncompass - cira WWII
From: Gary LaPook
Date: 2014 Sep 23, 22:15 -0700
From: Dan M <NoReply_DanM@fer3.com>
To: garylapook@pacbell.net
Sent: Tuesday, September 23, 2014 1:41 PM
Subject: [NavList] Interesting ebay find: Plath suncompass - cira WWII
Attached File:
(20140817_071730.jpg: Open and save)
From: Gary LaPook
Date: 2014 Sep 23, 22:15 -0700
Wow, it looks like a Bumstead sun compass on steroids. The face that we can see in the photo you posted shows it set for the northern hemisphere with the alidade rotating clockwise but it looks like it is universal and can also be set to work in the southern hemisphere. It looks to me that for use in the southern hemisphere you must take the dome and alidade off and remount them on the opposite face of the clock drive mechanism, do i have this correct? I also assume that the clock drive rotates a shaft on the opposite face in a counter-clockwise direction, is this correct? The original Bumstead sun compass came in two versions, one for the northern hemisphere (that looks like yours) with the rotation clockwise and one for the southern hemisphere with the rotation counter-clockwise.
See: prior discussions and photos:
gl
From: Dan M <NoReply_DanM@fer3.com>
To: garylapook@pacbell.net
Sent: Tuesday, September 23, 2014 1:41 PM
Subject: [NavList] Interesting ebay find: Plath suncompass - cira WWII
Fellow navigators, A few months ago I came across a Plath Sun compass on ebay.
To my amazement I bid and won. ( I think mainly due to no one knowing much about it – and for that matter neither did I ).
After some research I found out this instrument was used by the German military during WWII. Seems it was very useful in North Africa when transiting across the desert, or setting the magnetic compass in an aircraft. It has an ingenious 24 hr clock works that when set with GMT ( EQT applied), your Lat and Long it is able to maintain a true bearing ( or desired course) via the sun’s bearing via the diopter located on top of the instrument. The diopter focus the sun’s rays to a very fine beam of light.
Sadly when it arrived I found that the clock was in less than perfect condition. I wound it, it ran for less
than a day and failed. In that time frame sadly I wasn’t able to fully understand the operation of the instrument.
Enter Bill Morris: I had in the past communicated with Bill on numerous topics and obtained nearly all the manuals he provides for repairing Aircraft sextants. Given Bill’s vast knowledge I thought he may be willing to assist me in getting the Plath back up and working.
As luck would have it Bill visited the USA a few months ago. Great! I drove up the relatively short distance ( closer than New Zealand) and passed the Plath to Bill. We enjoyed a nice visit as well.
Shortly after our visit the Plath arrived back home via Fedex…… I immediately wound it up,
set the clock after further study on time setting - bingo! She works perfectly! How did I know it worked? In the past I’ve used an Abrams, Astro and Darra corrector sun compasses in my side line of magnetic compass correction. After setting the Astro and Abrams the Plath was true to form exactly in line with the true bearings obtained by both. The Plath of course has the added value of tracking without further corrections due to the 24 clock that drives the platform. As long as the time remains correct, your DR (or GPS position) remains keen you can maintain any desired bearing. ( unlike the Abrams and Astro that needs near constant correction to remain accurate due to the path of the sun). An amazing instrument to be sure!
Without Bill’s help the Plath would
still be on my display shelf in the study wondering how it worked..
See photo…. Someone seems to have taken good care of it for the past 70 plus years.
Attached File:
(20140817_071730.jpg: Open and save)
