Hi More help required - does anyone know what the 'Observer Instrument' looked like/did (even better if you have a photo I can use in a non commercial website). All I know about it is from a pamphlet 'Air Defence of Great Britain - Instructions for Observer Posts' dated 1938 but not much details given. It evidently involved a chart and some way of height finding of aircraft. Was this instrument in use throughout the war by the Observer Corps? Dave
Note the graduated scale in the sliding upright post... ...and although I haven't found an uncopytighted view of it yet, one of the horizontal bars also had a scale on it - therefore a sighting gave you a two-measurement reading. Distance vs. elevation? As far as I'm aware, the map underneath was a gridded map that allowed then to track the direction of flight crosscountry, and the whole piece of kit worked along the same general principles as a sextant.
Here's a relatively good view - see how the "sextant" tracks around the gridded map underneath? Grid ref by grid ref therefore, the track of a German raid could be mirrored on the "big board" at the respective Sector and Group controls
Here's a good view of the table! See the large numbers? I take it they mapped (sic) across onto OS map squares?... specifically the ones the ROC OP was sitting in?
Hi phylo roadking Yep that has to be it - the pamphlet talks about a chart on a circular table which has to aligned to a prominent object, already marked on the chart to allow this, in order to correctly be oriented to true North and south. The numbers do indeed refer to the old cassini squares. The pamphlet talks about recording either by sound (plotted on a square within a five mile 'sound' circle radius) or visual height finding (if the height finder is set correct then the position of the plane on the chart will be correct or, if the position of the plane on the chart is correct, then the height will be correct!) - this would have to be done by two or more posts working in conjunction. This instrument was certainly in use at the start of "the longest vigil in recorded history" - Aug 24th 1939 - was it in use throughout the war? Many thanks again Dave
I've attached a pic showing the top of the table. Red spots are neighbouring ROC posts; Attack Warning Red will tell you which they are (Maidstone group) and you can probably work out which post this one came from. This is in the Battle of Britain display at IWM London. Hope this is of interest! - Pete
Hi Pete Many thanks for the image - certainly of interest. Ps in my opinion Defence of East Sussex by far the best anti-invasion website on line, hope you get to do the book someday! Dave
Dave, in passing I saw something about a partial standown late in 1944, and earlier several thousands ROC personnel accompanied Allied forces into Europe - so a first guess might be "no"...not QUITE to the end of the war?
a Mark11a Instrument Well, that's a remarkable succinct and not-typically British understated name... with a Micklethwaite hieght correction attachment ....then they just had to go and do that!
Hi Pete Ps in my opinion Defence of East Sussex by far the best anti-invasion website on line, hope you get to do the book someday! Dave Hi Dave, Thanks! I'm actually starting to investigate publishing options at the moment; it's going to be a long process though, so don't hold your breath! - Pete
