NavList:

Again a great explanation, thanks. What a trove of information this group provides. I believed that perhaps the reservoir had to be sealed to make a counter pressure but your explanation makes perfect sense. So now there is a bubble and I can make it any size I want, see attached picture. When I suck air into the chamber there are several bubbles much in soap, but I can rid them one by one and select the one I want. Perhaps this is because I use Xylene and the Toluene-droplet that was already there doesn't mix very well?

The weather is overcast here for a few days so I cannot yet use the sextant and find its index correction etc, but compared to the A-12 against a terrestrial lamp post the angles seems to correspond. 

And now a few other things: 1/ The wheel on the right hand side does not run all that smooth, would some grease on selected gears make a difference? The mirror it self is greased and moves smoothly. 2/ I just noticed that a mechanical brake falls in and stops it a just short of 9 degrees, very odd. Any ideas on this?  And 3/ the spindle screw that moves the main mirror is constructed with a backlash so that going from one direction to the other does not move the main mirror directly. Is this really expected behaviour?

Anyway thanks for all help! 

Cheers Micke

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