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[Leovilla]

My maternal grandfather (died 1953) was a merchant navy Captain. My mother (died 2011) let me have what you see just before she died informing me it was my grandfathers from his days at sea.
 
When looking through the eye piece at any light it shows red.
 
Does anyone know precisely what this instrument is. I intend to keep it for my grandson and it would be nice to be able to explain to him what his great great grandfather used it for.

[furball]

Some sort of surveying instrument?


It looks like you could take a bearing through the eyepiece against the wire. I can't think why there would be a red filter in there though, unless it was to cut down glare.




Lance

[Netleyned]

A range finder for keeping distance in convoys.
The lateral bars are a bit of a mystery though.

Ned

[GAZOU]

 

this is a very powerful device

we put it on the ass of a chicken

and see if there is an egg

In Australia they have the same
but larger for ostriches

Now the X-rays are used     

[BrianB6]

Sorry to correct you Gazou.
We only have them for Emus down here.   It's the South Africans that use them for Ostriches.

[derekwarner]

 ....no ...not for egg sizing.... ......

But really is a "Mast Aligner"......similar in concept to a theodolite    ....but used principally for checking the vertical alignment of a mast  .....Derek

[tobyker]

It looks as if you could lay it on top of a large binnacle compass to take a bearing. Maybe the red filter is to retain night vision if you are taking a bearing on a lighthouse or masthead light?

[furball]

Google 'circumferentor', and have a look at the images, it looks like it could be part of one of those.


Lance

[w3bby]

I would have a guess at an "alidade" to be used in conjunction with a ships compass for taking bearings. You will find similar on  a prismatic compass.

[TailUK]

It's a Relative Bearing Indicator or Pelorus.  Used in conjunction with a compass, it's used to check the bearings to fixed objects or other vessels.  The red lens is for night use as the illumination could spoil an officer's night vision unless viewed through a red filter.

[jaymac]

methinks perhaps the red filter is to reduce the glare from the boiler fires whilst measuring ''The Golden Rivet'' 

[MikeK]

Beat me by 9 minutes TailUK ! It is indeed a Pelorus used for bearings. The 'arms' fit neatly on the compass/repeater top without any play enabling it to be swivelled around the top

Mike

[TailUK]

Sorry Mike!  Leovilla's example should be made in Brass, another non-ferrous metal or have a hardwood frame to prevent the device from interfering with the compass.  Another name for the pelorus was "dumb compass"

[Leovilla]

Thanks gents. It is indeed made of brass. It has its hardwood box which sadly is in a bit of a state.
 
 Any idea what age it may be and when they were first used..

[TailUK]

The name Pelorus dates back to Hannibal's Navigator in 200BC.  The instrument was named for him.  The earliest reference I've found fter a couple of minutes digging was to 1912.  Titanic was fitted with 2 Peloruses (Pelori?) One on each bridge wing.  I should imagine that such a navigational instrument goes back a lot further possibly hundreds of years.
Yours looks vaguely military and may have found it's way onto a merchantship as the personal property of an officer or as military surplus.  The night vision lens also suggests military use.
From a little experience with instruments I'd hazard a guess that this is 1930's to 1940's, give or take a little.

[GAZOU]

Titanic was fitted with 2 Peloruses (Pelori?) One on each bridge wing

The night vision lens also suggests military use.


it was the same ?

[Jerry C]

It's an azimuth mirror used with a compass which has a center pivot point bonded to the top glass. It may also be used with a pelorus. A pelorus is similar to a compass but has no direction keeping properties. It is used to measure relative bearings which when applied to the ships head give compass bearings.
Jerry.

[MikeK]

Good old Hannibal, sailed with him when he was apprentice. Not that that has any bearing on the subject !
Geddit ?

Merry Xmas one and all

Mike