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APM SD 140 F7 Apochromatic Refractor OTA
Using a 140mm SD doublet, the APM SD 140 F7 Apochromatic Refractor OTA combines a 980mm focal length, f/7 optics, and a 52mm image circle for listed imaging applications.
- The 140mm aperture has 0.83-arcsecond resolving power
- 980mm focal length uses f/7 optics
- 2-element SD doublet with FPL-53 glass
- 3.7-inch focuser provides 10:1 adjustment
- 52mm image circle supports large-format coverage
- 15kg equatorial mount capacity is specified
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Description
Most doublets ask you to choose between weight and color correction. The APM SD 140 F7 skips that trade-off with an SD doublet built around FPL-53 equivalent glass, the same grade of ED element used in premium triplets, closing the color-correction gap while staying under 10kg.
At f/7, this 140mm refractor favors wide-field speed over the long-focus precision of APM’s slower triplets, and at 9.8kg it’s the lightest large-aperture APO in APM’s current range — easier to balance, easier to mount, and needing only 15kg of payload capacity. This OTA ships without a mount or tripod, so budget for that separately before ordering.
Key Features of APM SD 140 F7 Apochromatic Refractor OTA
A 2-element air-spaced SD doublet using FPL-53 equivalent glass pushes color correction well past a standard ED doublet, at a fraction of a triplet’s weight.
- FPL-53 equivalent SD glass narrows the color-correction gap with full triplet apochromats
- At 9.8kg, this is the lightest large-aperture refractor in APM’s current lineup
- f/7 focal ratio favors wide-field deep-sky framing over long-focus planetary work
- 52mm image circle covers large-format sensors for serious astrophotography setups
- 3.7-inch rack-and-pinion focuser with 10:1 dual-speed micro-drive holds focus under a full imaging train
- Carrying handle built into the tube rings makes solo setup manageable
- 2-inch and 1.25-inch reducer adapters ship included, covering multiple camera formats
- Magnification range from 20x to 280x balances wide framing with planetary detail
Why Choose the APM SD 140 F7
Against APM’s full triplets, the SD 140 gives up a small amount of ultimate color correction for a lighter tube, a faster f/7 ratio, and a lower mount requirement — a fair trade for anyone prioritizing wide-field deep-sky work over the long-focus planetary precision a triplet is built for. Against a standard ED doublet, the FPL-53 equivalent glass here is the real upgrade, pulling color correction closer to triplet territory than a basic ED formulation reaches.
Applications & Use Cases
Built for high-resolution wide-field deep-sky astrophotography with medium or full-frame sensors, this refractor also handles high-contrast lunar and planetary observation.
- Astrophotographers who want near-triplet color correction at doublet weight
- Imagers prioritizing wide-field framing over long-focus planetary detail
APM Warranty & Support
The SD 140 F7 carries a 2-Year Factory Warranty covering manufacturing defects on the optical tube and focuser assembly, handled directly through APM’s support channel.
APM SD 140 F7 Apochromatic Refractor OTA Specs
| Brand | APM Telescopes |
| Full Model Code | APM-SD-140-F7-OAZ |
| Country of Origin | Germany |
| Optical Design | Doublet Refractor (2-Element Air-Spaced SD Doublet with FPL-53 Equivalent Glass) |
| Aperture | 140 mm (5.51 inches) |
| Focal Length | 980 mm |
| Focal Ratio | f/7 |
| Optical Coatings | Broadband Multi-Coated |
| Secondary Mirror Obstruction | 0 mm (0%) |
| Secondary Mirror Obstruction by Area | 0% |
| Backfocus Distance | 180 mm from end of extension tube |
| Rear Cell Thread Type | M92x1 Internal Thread / M68x1 Internal Thread Adapter |
| Image Circle Diameter | 52 mm (Optimized Large-Format Astrophotography Coverage) |
| Resolving Power | 0.83 Arcseconds |
| Limiting Visual Magnitude | 12.5 |
| Highest Useful Magnification | 280x |
| Lowest Useful Magnification | 20x |
| Optical Tube Material | Aluminum |
| Focuser Style & Mechanism | 3.7-inch APM Rack and Pinion Focuser with 10:1 Dual-Speed Micro-Drive |
| Mirror Lock Mechanism | No (Refractor Tube Configuration) |
| Optical Tube Dimensions | 152 mm x 830 mm (transport length with retracted dew shield) |
| Optical Tube Weight | 9.8 kg (21.6 lbs) |
| Mount Attachment Type | Losmandy D-Style Dovetail Plate with aluminum tube rings and carrying handle |
| Finder Scope Specification | Not Included (Mounting base bracket integrated) |
| Included Accessories | Aluminum Tube Rings, Retractable Dew Shield, 3.7-inch Focuser, 2-inch and 1.25-inch Reducer Adapters, Carrying Handle |
| Power Requirements | None |
| Standard Warranty | 2-Year Factory Warranty |
| Application | High-resolution wide-field deep-sky astrophotography with medium/full-frame sensors and high-contrast lunar/planetary observation, requiring an equatorial mount with a minimum payload capacity of 15 kg. |
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