Construction

Construction

Mark III ultralight dobsonian telescopes

Construction Techniques and Materials

	Finnish Birch or Appleply plywood is used throughout for its high strength, low water absorption, and good looks. All joints are tongue-and-groove to increase strength. All wood surfaces are sealed with multiple coats of outdoor polyurethane.
	Struts are made from seamless 6061-T6 aluminum tubing with a minimum wall thickness of 0.049".
	The mirror "box" is essentially a fiberglass tube with end rings. The outside of the tube is made from Ebony Star laminate to match the altitude bearings. The inside has been coated with fiberglass to make a lightweight, rigid tube.
	The bearings are 1" thick. The bearing surface is 3/4" wide and coated with Ebony Star laminate. The bearing surfaces rest on virgin Teflon pads. Each bearing has a 1/4" raised lip that keeps the optical assembly centered in the rocker box.
	The focuser shelf is custom-made from thick aluminum angle stock to provide rigid support for the focuser.
	The bottom of the mirror box is covered with Ebony Star laminate. It rests on virgin Teflon pads attached to the ground board.
	Fasteners and other hardware are made from stainless steel, aluminum, or other corrosion-resistant materials.

Components

The lightweight primary mirrors are manufactured by Swayze Optical.

	The 12.5" mirrors are <1.5" thick and come with the standard aluminum coating (90% reflectivity) or an optional enhanced aluminum coating (96% reflectivity).
	The 18" primary mirrors are 1.5" thick and also come with the standard aluminum coating (89% reflectivity).

I also can use other sources for primary mirrors.

	The secondary mirrors are typically 1/10th wave or better and supplied with an enhanced aluminum coating (94-96% reflectivity).
	The optimized six-point floatation cells for the 12.5" primary mirrors are manufactured by LightWare. It provides excellent support while maintaining the lowest possible center-of-gravity. Primaries are attached to the six support points using silicone caulk.
	The 18" primary mirror is supported by a 18-point floatation cell, also made by LightWare.
	The secondary spider and holder are supplied by Novak or ProtoStar.
	The standard focuser is the 2" NGF-DX2 on the 12.5" and 18". These focusers are of the Crayford design, and are purchased from JMI. Each comes with the 2" to 1-1/4" adapter.
	Two Kydex light baffles are supplied: one for the upper ring opposite the focuser and one for the front face of the mirror box.

Please contact us if you have any questions.