Wednesday, March 6, 2013

Guiding a Camera on GM-8

The images below show how I have configured a guider for my DSLR on my Losmandy GM-8 equatorial mount.  Starting with a short Losmandy-D dove-tail plate, I mounted two Orion-style finder mounting shoes on one end of the plate.  I had to saw off part of one of the shoes that extends down so that it would sit flush on the plate since the available mounting hole was too close to the edge.  On the other end of the plate, I mounted a Manfrotto 496RC2  ball mount with quick-release plate.  I mounted a red-dot finder on the inner shoe to help align the mount and find targets.  I installed an Orion Magnificent Mini AutoGuider package on the other shoe.   This is the same finder and guider that I normally mount on my 80mm refractor so that much less stuff to carry around.

One of the problems I had mounting a simple camera on this mount was that there is not enough weight to counter-balance.  To solve this problem, I inserted a 1 lb counter-weight with 3/8"-16 threads. between the plate and the ball mount.  These weights are intended to be screwed onto the end of the counter-weight shaft.  One weight under the ball mount and two weights on the end of the shaft balanced each other almost perfectly - without, of course, the 7lb weight normally used to balance a telescope.  The plate is also offset from center by about an inch to balance side to side.

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