NavList:

Thanks very much Dave. An interesting bit of background. I knew about the light as it's similar to the MKIX. Everything's working now. Got a couple of moon sights last night which worked out nicely. Both inter epts were short by 3 miles I presume thats the expected accuracy. Certainly very easy on a window ledge. Thanks for that tip. Took a while for my slow brain to work out the light is coupled to the averager not a shutter like the IX. The circuit diagram helped with that. I'd be really interested to see the rest of the diagram showing the pendulous mechanism. I usually take my sextants apart and have a look inside but the 2A seems to be impregnable. My Hercules flights were as an air cadet in the far east in the late 60s. Spent many happy hours on the bench seat at the back of the cockpit. They were brand new at the time. Amazing that they are still flying. Thanks again for the help.