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Paul Dolkas you wrote: Dave-So how exactly do you use a needle to insert bubbles into an A-12?

Paul
I only used the A12 as an example.  In truth, it’s been a few months since my A12 was at the centre of my attention, and I can’t remember.  I just kept ordering finer and finer needles on eBay until I got one to fit.  I notice my finest is 26 Gauge (0.4mm); maybe it was that one alough I've still got a strip of 10 so maybe it was 22 Gauge.  The trouble is the fewest needles of any one gauge you can buy from China on eBay is ten, so I ended up with quite a collection of syringes and needles.

Maybe I never got chance to try the narrower needles, because I got myself into other fine messes around the same time.  At an earlier stage, I had the great idea of sealing the little filler screw and the edges of the viewing windows with varnish.  Bad idea; the vanish found its way down to the little ball, and now it’s immovable.  Worse still, the idea didn’t work; my bubble still grew.  I suppose I could try acetone to loosen the little ball, but I’d need to be careful to keep acetone off the windows.

Then, having paid through the nose for a set of Bristol Keys from the USA so I could work on the bubble chamber, I thought I might as well use a larger key from the set to give the index mirror a little tweak.  What do they say about ‘good intentions’?

As a final insult to Mr Link, my attempt to glue a fiduciary black spot at the centre of the window to help me hold the sextant level was also a failure.

I’m sure I read somewhere about that time of the best way to hold a bubble chamber whilst filling it, but once again, I can’t remember where. DaveP