The new William Optics Star71-II imaging telescope replaces the venerable first generation of this telescope introduced in 2014. The Star71 is an excellent, portable, high-quality apochromatic astrograph with a built-in flattener for the astro-imaging enthusiast.
How does this differ from the 1st generation Star-71 telescope?
- Mechanically, the two scopes are virtually identical.
- Optically, their performance is identical too. The key difference is that the first generation Star-71 had a five-element design out of which only one element used FPL-53 ED glass. This second generation has a new four-element design using two FPL-53 ED lens elements. William Optics retained the same optical design parameters and performance, but the new design is much easier to collimate during assembly.
- The new tube features a Vixen-style dovetail base for attaching finder/guider brackets.
- A soft padded carry case is now included as a standard accesorry. It was sold separately earlier.
- 71mm f/4.9 imaging refractor telescope with 350mm focal length
- Two FPL-53 ED glass elements for color free apochromatic performance
- 4 element design with built-in field flattener. This is a new, patent-pending design and the optical configuration is not being disclosed at this time.
- Covers 45mm full frame imaging circle
- 2.5" dual speed R&P focuser
- Includes soft padded case, mounting rings, Vixen-style dovetail rail, and an M48 Canon EOS adapter
- Weight = 4.5 lbs / 2.05 kg (OTA only); 5.3 lbs / 2.4 kg (OTA with rings and dovetail)
- Focuser drawtube travel = 1.38" / 35mm
- Back focus = 71.3mm from 48mm Canon thread (see pdf attachment below for details)
- The focuser drawtube terminates in a male M48x0.75 thread. This telescope comes with a wide M48 female threded Canon EOS adapter ring. Similar rings are available from other suppliers for other brands of cameras. Note that this a not a conventional 2" focuser tube with locking thumbscrews.
- An optional 1.25" 90-deg dielectric mirror diagonal is available separately for those wishing to use this as a visual scope. This diagonal comes with a custom adapter that connects directly to the M63 female thread on the telescope's focuser tube. You cannot attach standard 1.25" diagonals and the telescope cannot reach focus with larger 2" diagonals.
Specification for ED Lenses
All William Optics refractor objectives are double tested and inspected by WO at their factory. These telescopes are free of coma and astigmatism. Since all individual lens surfaces are machine coated, sometimes you may notice visual imperfections which will not compromise the optical performance of the telescope. THe dimensions of scratches and points shall not exceed the following values:
- Scratches - Maximum Width: 0.025 mm
- Scratches - Maximum Length: 1/4 of total lens diameter
- Scratches - Maximum Quantity: Three
- Dots or Spot Points - Maximum Diameter: 0.4 mm
- Dots or Spot Points - Maximum Quantity: Three
- Accumulation of Defects - Limited Area: 0.8mm^2
- Accumulation of Defects - Total Area: 5.8mm^2
- Charles Bracken's Review of the Star 71 (This is a review of the discontinued first generation of this telescope)
- Astronomy Technology Today Article - The William Optics Star71 Refractor by James R. Dire, Ph.D. (This is a review of the discontinued first generation of this telescope)