14 inch Horseshoe and Observatory by Mel Bartels
Aperture
fever was really kicking in, so I built a 14 inch. Actually I was a
victim at an early age, lusting after the 8 inch in the back of the
Edmund Scientific catalog. The 14 inch used a simple but highly
effective drive system consisting of a worm and gear 30:1 reduction
driving a machined drive shaft that the horseshoe rode against. There
was no detectable periodic error during guiding. I used a double
diagonal guiding arrangement of my devising, where the camera's
diagonal was made purposefully slightly undersized, allowing a bit of
light to escape around the edges where it was collected and used for
guiding. This reduced the light going to a camera to an aperture of 12
inches, but sent light equal to a 7 inch scope to the guider. Besides
the bright guiding image, I could also guide exactly on the object I
was imaging - no off-axis star images here. I also built a color
enlarger, large format projector and a blink comparator. I used
sonotube for the tube and 3/4 inch Birth plywood for the mount. As you
can see, the tube rotated on bearings.
An
example of the cold camera prints from the scope, camera and enlarger.
A 5 minute unguided astrophoto of M42, taken from the suburbs.
I moved the 14 inch to a roll off observatory, where the entire observatory moved on plastic pipe.
eod