Camera Tilt

[Tom Droege <tdroege2@earthlink.net>]

I thought I should discuss the camera tilt and what I am doing about it.

In an ideal world, the two bars, the two bearings near the camera,  and the 
camera form a parallelogram.  When the weight of the camera bends the bars, 
the plane of the camera should stay perpendicular to the axis of the 
lens.  I assumed it would displace, but this is not so important on the 
scheme of things where we are taking a survey and not trying to point to 
any particular place.

Because the bars are only constrained at the camera end, the bars can bend 
in an arc.  The upper bar then slides out more than the bottom bar and the 
length of the bars out from the bearings becomes uneven.  This gives two 
problems.  The camera tilts, and the bars want to stick as the motor drives 
them in and out.  This makes focusing a problem.

Anyone who has looked at a trombone will notice a stiffener half way down 
the parallel tubes.  This serves as a place to grab for the player to tune 
the instrument.  But it also stiffens the tubes and prevents the problem we 
have with the Mark IV.

I have designed stiffeners to use on the Mark IV.  They are out being 
made.  Note that where you really want to put them is right through the 
lens.  This is not possible, so I had to design funny bars that wrap around 
the lens.  Sigh!  I have designed the Mark V properly so that the camera 
cannot tilt.  Well, it can still tilt a little, but several orders of 
magnitude less.

Tom Droege