A new big-aperture refractor providing top-class optical and mechanical performance to appeal to apo aficionados.
Plus: Excellent optics and mechanics; suitable for both visual and photographic use
Minus: Heavy, though solidly built; some vignetting with optional reducer/flattener
Summary: The SharpStar 140PH is a superb large-aperture triplet apo at an attractive price given its high-end performance.
Who Is It For? Aficionados of premium optics looking for a first-class apo without the extreme prices and wait times of some competing brands.
No telescope carries more prestige — and price per inch of aperture! — than a large apochromatic refractor. While smaller “apos” can be affordable, only those who prize the sharp, high-contrast images of this design can justify the expense of an apo over 100mm aperture.
The SharpStar brand from China is a new entry to the apo market, with models at attractive prices . The company has made telescopes sold under other brands, but it is now offering telescopes under their own SharpStar name.
With samples supplied on loan by All-StarTelescope.com, the Canadian dealer for SharpStar, I tested SharpStar’s smaller 76mmEDPH triplet and 100mm quadruplet astrograph, and was very impressed. But for those who want aperture, the 140PH is the largest refractor in the SharpStar line, with a 140mm f/6.5 triplet lens featuring two elements made of unspecified ED glass.
Refractors this large can be prone to optical issues caused during lens manufacturing and mounting, so I was pleased to see no aberrations or flaws that would take this telescope out of the first-class league. Color correction was as good as I have seen with other premium apos, and I have owned and used the best. On cold nights there was no astigmatism from pinched cells. In-focus stars presented near textbook-perfect Airy disks. The only visible flaw was a trace of spherical aberration in extra-focal star images.
The focuser is a massive 4-inch rack-and-pinion with a smooth and precise 10:1 dual speed adjustment. It racks out over a generous 110mm range and locks securely. The entire focuser can rotate, while the back end has a lockable camera angle rotator as well. A dovetail bracket on the focuser accepts a user-supplied finderscope. The telescope comes with a solid traveling case, but does not include a star diagonal or finderscope. The 140PH delivers superb views with its 5.5-inch aperture, just shy of much costlier 150mm (6-inch) apos.
Photographically, at its native f/6.5 and 910mm focal length the 140PH provides a flat field over the central 25mm of a full-frame (24x36mm) sensor, more than enough for use as is with smaller sensor cameras.
For a better corrected field, the optional three-element 140PH reducer/flattener provides a faster f/4.8 focal ratio and an effective focal length of 670mm, providing a field flat to the corners of a full-frame sensor. Light fall-off at the corners was one f-stop, which isn’t bad, though I would have expected better field illumination considering the size of the reducer/flattener.
The SharpStar 140PH is an impressive visual and photographic apo with an attractive price for its aperture and performance. If I didn’t already own a premium 130mm apo, I’d be tempted!
SharpStar 140mm triplet apo refractor: $4500
Optional Reducer/Flattener: $400