Hawks Landing Observatory
Poway California
Observing in Suburban Night Skies
Inside Hawks Landing Observatory.
The observatory houses a 14" Planewave, f7.3, modified Dall-Kirkham (mDK) telescope, sometimes referred to as a Corrected Dall-Kirkham telescope. What? An mDK is really different from a classical Newtonian reflector telescope. Isaac Newton invented the "Newtonian" telescope back in 1668 by grinding a parabolic mirror from "speculum" - a metal alloy composed of tin and copper. What he realized was that the parabolic mirror will reflect all light rays coming into the telescope into exactly a single focal point - the place where you would place your eye.
An mDK telescope has an elliptical primary mirror as opposed to a parabolic mirror in a conventional Newtonian telescope. For the secondary mirror, the mDK telescope has spherical secondary mirror and not a flat elliptically shaped mirror as in the classical Newtonian Telescope. In addition the the mDK configuration also includes a lens group (usually two or three lens elements) ahead of the focal point to improve off-axis image quality.
"One practical benefit of the mDK design is that collimation of the convex spherical secondary mirror with respect to the optical axis of the primary mirror is almost trivial, (theoretically but frustrating in reality) because there is no single defined axis of a sphere. Any line that runs through the center of the sphere can be an axis." Reference: wikipedia
Planewave 14" f/7.3
As you can see, the 14" Planewave telescope is rather small. But small doesn't mean inexpensive. Oy! What distinguishes this little diminutive telescope is its flat fields for astrophotography. On a normal Newtonian telescope, such as the popular Dobsonian telescope, the best sharpest image is in the center of the eyepiece. While using just your eye, this is fantastic. But let your eye wander to the edges of the field of view, you may notice the stars appear as little comets. That distortion is called coma. For visual observing that's ok. We really don't notice it. But take a picture and your eye sees the stars with coma.
So besides cost, what are its disadvantages? It's the center obstruction from the secondary. The secondary on the 14" is 49% the diameter of the primary mirror, or 24% by area. So this 14" mDK has the light gathering power of a 12.1" refractor with no obstruction!
My all sky camera runs mostly continuously every day and night. Installed with the all sky camera is the Boltwood weather monitor (on the left) and the Unihedron SQM Sky Quality Meter housed in the PVC pipe on the right. Note the two gray vertical PVC pipes are only structural and otherwise non functional.
Using the AllSkEye software, the ZWO camera plots the brightest stars and asterisms are plotted from a catalog. The camera is a ZWO ASI 178MC. The software that processes all the images if All ALLSKEYE by Michael Poelzl. When the moon is above the horizon the detection of stars is minimal at best. Over the last 5 years, seeing ha steadily worsened and the evening sky is blanketed with high haze which enhances the impact of light pollution.
The SQM measurements are provided on the page "Real-time status".
Hawks Landing Observatory at Sunset
