March 03, 2010

WWII Astro Compass Mk2

Hello Folks

I thought we could step back into WWII History and take a look at an item I have just added to my collection.

Over the last 20 years I have put a display on at the Norbrek Radio Rally in Blackpool. Although I refer to the items I have as a collection, they are not something hidden away never to be seen by anyone but close friends, but rather, something that can be touched and examined by people.

Many of the items would not normally be seen unless you visited a museum. Nothing pleases me more than when two or more people gather around an exhibit and get into a discussion about it, many times its an older radio amateur explaining how something works to a younger family member of new amateur.

Ok enough waffle lets get down to business.

You may have noticed that this item has nothing to do with radio communications and everything to do with navigation.

The British Version of The Astro Compass

Until today I had trouble finding any information on the British version of the Astro Compass but found the following information on Ebay supplied by "Wing, Rutland, United Kingdom" on the British Version of the Manual and a little history.

(This is a re generated print (not a simple photocopy) of what I believe to be the original handbook issued with the Astro Compass Mk II and IIA ( RAF ref 6A/1174) during and after the last War. There is a serial code on the original suggesting Canadian printing in 1942. The original had no illustrations so I have, for clarity, added two of my own at the back. Several points suggest the original may have been a very small booklet similar to the Bubble Sextant's but untill I know the correct size I am printing it as A5. There are 16 pages A5, black and white with two illustrations. Subjects covered are:- Principles of operation, Construction and field re tensioning of pivots, Checking true heading by Sun, Moon, Planet and Star. Steering a course. Obtaining the true bearing of a distant object. Methods to check alignment of the compass. In fact, after reading the booklet you will probably assume everyone should have an Astro Compass, they are so usefull. I even have an article on converting one for use as a simple Dumpy Level! There are other, American versions of the Astro Compass, the original being the British version developed by Mr. PF Everitt of H Hughes and Son. I have manuals for only one of them, the Sperti Company . If you suspect you have an American version mail me for identification. For a more detailed view of the Astro Compass I would recomend reading AP 1234D, I do a reprint of the Astro compass section. Postage (UK) £1.50)

W.W Boes Co. & Sperti.Inc

There was two company's who made the Astro Compass in the USA, W.W Boes Co. and Sperti . Inc.

So far the only difference between the two companies has been that

1. W.W Boes.Co housed their compass in a Bakelite box
2 They used a transfer type name plate
3 The operating instructions were printed in colour with a little artwork on the front cover

Bakelite box

Transfer type Nameplate

The Operating Manual was blue in colour with graphics depicting a plane. If you cut & paste the link below into your internet Browser the manual is available free in pdf format.

Sperti Inc.
1. Came in a wooden box in my example the box is painted RAF Blue with a white canvas strap with the words Astro Compass MkII stenciled on the front side of the hinged lid and "Delicate Instrument to be Handled with Care" Stenciled in red on a while background in the front of the box.

Here's some pictures I have taken of my Astro Compass MkII

2. The name plate containing information on what the item was, Its parts and serial number and AM indicating the instrument was made for the "Air Ministry" was stamped onto the chassis of the instrument and highlighted as white lettering.

3. The front of the manual was plain without graphics, but there were pictured inside along with the operating instructions identifying the various parts of the compass.


In 1942 Sperti changed its name from "Sperti Products" a company that made sun lamps, to "Sperti Inc." a company that made products for the US Airforce and Navy. One of the products made was the Astro Compass which went into service in 1942.

If you would like to learn more about the company up to the present day, use the link below.

The link below will allow you to download the manual

It would seem that the manufacture of equipment like the Astro compass followed a similar road to that in the UK where manufacturers were given defense jobs unrelated to there civilian production line.

Here are some more of the pictures of My Astro Compass starting with the boxed unit and then working top to bottom starting with the sight. The unit was not supplied with the base for mounting to an aircraft etc, this stand was bought separately.

Boxed Astro Compass

Sight used for both Sun and Stars

Bubble levels

Socket that took the base and screw adjusters for leveling

Once the Astro Compass had been aligned an Air Almanac could be used to successfully plot your location

I have seen reference to the Astro compass being fitted to the Lancaster Bomber, The American Liberator,and the B25J Bomber shown below.

An Astro compass fitted in a B25J Bomber. For more information on this aircraft and the Astro Compass please visit the site below where you can see this image along with many others. A really interesting site.

The RAF Millom Air Museum is well worth a visit if your ever in the area. It's very deceptive from the outside looking rather small but once through the door it's like the TARDIS as you walk from room to room that's full of interesting exhibits, including photographs and information on RAF Morecambe.

Take a look at the sites listed below, which include reference to the Astro Compass MkII. It's time well spent.

The second site is a great document covering an excavation conducted by Tony Robinson and Time Team.

Although not on communications I hope you have found this blog interesting, and its not long before you visit us again.

One might think that the Astro compass was last used in the far and distant past, but nothing could be further from the truth. Area's of the world that have a strong magnetic field render normal compasses useless and in some cases it has been made law that an Astro Compass is carried.

Best 73
Brian G0RDH


Marty in Grass Valley, CA said...

I live in Northern California, and a friend just found - and bought - an Astro Compass Mk-II at a church yard sale. He isn't interested in computers and the internet, so he asked me to look for information about it. I thoroughly enjoyed the search. Your article is the best of all I found.

I'm a civil engineer, so I had a couple of surveying classes in college. I assumed he was describing a theodolite. I was close.

My buddy Bob is a retired telecommunications engineer, and loves mechanical things. We'll enjoy trying to come up with ways to actually use it.


Anonymous said...

Thanks for the info on what this thing is! I've had one for a couple of years now and always had fun showing it and guessing what it might be with soon as I found out what it was I had to find more info on it and your manual was perfect-Thank you for sharing it!

Anonymous said...

I just bought one of these because I am a surveyor and figured it was a device for using the sun and stars for navigation based on my inspection. However, your information not only confirmed I was correct, but added so much more with regards to history, usage, and even the manual!!! Thank you so much for posting this information on this unique piece of scientific equipment. Interesting that it is still in use in some places today, although I would imagine that GPS has mostly replaced it. Thank you again for the information and for making the scanned manual available.

Northern California

Anonymous said...

My Father Has One In A Box, MINT with the instruction manual in just as good of shape, he thought it was a Surveyors transit, imagine his surprise when he found out its a navagation device for a b25, very informative, thanks for the info

willymcneil said...

Hi i have this compass and also an astro.mk2 morse coder i cant seem to find any info.on the morse coder. i would appreciate any info you could provide and also do they have any value