Review: APM 140mm Doublet ED Apochromatic Refractor

The APM 140mm doublet ED apochromatic refractor. Credit: Larry Carlino

The APM 140mm doublet ED apochromatic refractor neatly fills the gap between some very capable 5-inchers and the much more difficult-to-mount 6-inch instruments. With a clear aperture of 140mm (about 5.5”) the APM is an f/7 doublet design using a combination of FPL-53 and lanthanum glass.

The result is a fairly light (about 19 lbs or 8.5 kg) and short telescope that can use a medium-weight mount to achieve reasonable stability. The scope boasts a retractable dew shield, Losmandy-type mounting plate, a convenient carrying handle, and Synta-style shoe for attaching a finder. Available with either a 2.7- or 3.5-inch dual-speed focuser, the instrument’s aluminum tube is an attractive mother-of-pearl white, complemented by a pair of black hinged tube rings. Overall fit-and-finish is excellent.


So, too is the optical performance. Color correction of ED doublets is frequently called into question, but this APM is sensibly perfect, at least for visual observations. Only at absurdly high magnification (300x or more) does the telescope show a very slight violet edge around Venus and Vega, and a thin green sliver kissing the limb of the full moon.

Jupiter, with its wealth of low-contrast detail, was a wonderful sight at 140x to 196x: visible was intricate bluish festooning punctuating the yellow background of the equatorial zone, and the ruddy coloration of the North Equatorial Belt filled with plumes, strings, and knots. Direct comparison with legendary Takahashi FS-128 and FS-152 fluorite doublets showed that the APM was just a small step behind in color saturation and “etched intensity” of the image.

Likewise, Saturn, its rings almost fully opened to our line-of-sight, was spectacular at 163x. The Cassini Division, ring and planet shadows, north equatorial bands, and dusky north polar area all stood out with marvelous clarity.

The 140x also performed well on multiple stars. The very tight (.9”) Nu Scorpii was neatly resolved at 196x, and the unequal magnitude Delta Cygni was easy at the same magnification. Images were tight and clean with a thin first diffraction ring.

Even with just 5.5” of aperture, the inherent contrast and excellent light throughput of the APM provided some fine deep-sky views. Open clusters such as M25, M11 (The Wild Duck Cluster), M37, M35, and many others were impressive, and the globulars M13 (Hercules Globular Cluster), M5, M22 were easily resolved at medium powers. Diffuse nebulas M8, M17 (Omega Nebula), and the Orion complex stood out beautifully, especially when aided by an OIII filter.

Overall, the APM 140 strikes me as an excellent instrument: just the right size, right price, and quality to be perfect for many observers.

The Good: Quality optics, excellent fit-and-finish, reasonable price

The Bad: Not quite the equivalent of ultra-high-end scopes

MSRP: €2890 (2.5″ focuser), €3190 (3.7″ focuser)

MSRP: $2695 (2.5″ focuser), $3095 (3.7″ focuser)


About Larry Carlino

Larry Carlino is an avid, life-long astronomy enthusiast, lunar, planetary, and deep-sky observer and the owner of more than 100 telescopes over the past several decades. He is a writer, a poet (latest work "Between") and a retired teacher of English.

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