Scope of the Project

Project 40 Drawing - Perspective View  Scope

Project Description

Project 40 is a Valley of the Moon Observatory Association (VMOA) initiative to build a 40-inch refracting telescope that can be installed and used in the Robert Ferguson Observatory for public astronomy. The project was inspired by an earlier telescope built by the astronomy groups that were predecessors to the VMOA. That telescope has a flawed mirror that is too thin to refigure and polish. The VMOA undertook Project 40 to replace that telescope with an instrument that has great light gathering power, is easy for docents to use in public events, and is easy for visitors to use and enjoy.

Project 40 has set itself several goals to make the new telescope as useful as possible to the VMOA in its mission to bring astronomy to the public.  First, the optical path must end in an eyepiece at or near sitting height off of the floor. Second, the telescope must be constructed with visual astronomy as its first priority, with instruments only added if they can be integrated in a way that will not interfere with visual astronomy.  Third, the telescope must be easy for docents to use to find an object and to keep the telescope pointed at that object without frequent adjustments.

The Project 40 team chose to build the telescope as a <optical design type> with a parabolic primary mirror, hyperbolic convex secondary mirror, and flat tertiary mirror.  The design will use the partially completed truss tube design for the Optical Tube Assembly (OTA), and an altazimuth mounting that will be driven by computer in both axes to track a found object in the sky.  The telescope will be designed to fit in the west wing of the Robert Ferguson Observatory, a 20-foot by 20-foot enclosed space with a roll-off roof and an existing set of three piers.

The VMOA acquired a 40-inch telescope project that was already being built by an amateur telescope maker in Stockton, CA to start the project. The acquired parts include:

  • 40-inch mirror blank, ground to F/3.2 at the 200 grit size, including the mirror grinding tool
  • Mirror cell with 27 point flotation supports
  • Secondary cage with secondary spider mounting
  • Trusses
  • Azimuth aluminum bearing surface ring

To complete the telescope, the VMOA must:

  • Complete the grinding, polishing and figuring of the primary 40-inch mirror
  • Make or buy an 11-inch hyperbolic convex secondary mirror
  • Make or buy a 2-inch flat tertiary mirror
  • Test each of the optical surfaces and test the integrated optical system
  • Design and construct a rockerbox mounting for the primary mirror cell and truss OTA
  • Design and construct a tertiary spider and mirror adjustment
  • Modify and constuct a secondary spider and mirror adjustment
  • Design and construct an aziumth and altitude drive system
  • Adapt and construct a drive control system from the BBAstro Inc. design
  • Test the mounting and drive system
  • Integrate the optical components and the mounting
  • Test the integrated telescope
  • Install the telescope at Robert Ferguson Observatory
  • Publish instructions and provide training to docents on how to operate and maintain the telescope
  • Make adjustments to the mechanical and optical performance of the telescope during it’s “shakedown” period

The VMOA committed to raising up to $25,000 to complete this project. The VMOA Board estimated that it would take about 5 years to complete, starting in 2003. So far, the VMOA has spent $5,000 for the initial purchase of the partially completed telescope, and has raised about $5,000 in cash from corporate and individual donors.


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