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APM CNC-LW II 203/1800 Refractor OTA
Designed around a 203mm Super ED triplet, the APM CNC-LW II 203/1800 Refractor OTA provides a 1800mm focal length, f/8.8 optics, and long-focus imaging capability.
- The 203mm aperture has 0.57-arcsecond resolving power
- 1800mm focal length uses f/8.8 optics
- Three-element Super ED apochromatic design
- 3.5-inch focuser provides dual-speed adjustment
- 60mm image circle supports medium-format coverage
- 50kg equatorial mount capacity is specified
In Stock
Description
Same 203mm aperture, same 0.57-arcsecond resolving power as the shorter 1420mm version in this line, but a longer 1800mm focal length changes what the tube is actually built for. At f/8.8, the APM CNC-LW II 203/1800 trades field width for image scale, favoring high-power visual work and precise binary star measurement over general wide-field imaging.
This OTA ships without a mount or tripod, and at 26.5kg it’s the heaviest tube in the entire CNC-LW II line, needing an equatorial mount rated for at least 50kg once a full imaging train is attached. That extra focal length is the point: longer focal length means more arcseconds per pixel on your sensor, which is exactly what separating tight double stars or resolving fine planetary bands demands.
Key Features of APM CNC-LW II 203/1800 Refractor OTA
The same 8-inch, 3-element Super ED triplet used in the shorter 1420mm model gets stretched to a longer 1800mm focal length here, built for high-power precision rather than wide framing.
- Longer 1800mm focal length delivers more image scale per pixel, ideal for tight double star separation
- f/8.8 ratio favors high-contrast planetary and lunar detail over wide-field speed
- 0.57-arcsecond resolving power matches the largest aperture in this series
- Starlight Instruments Feathertouch dual-speed focuser holds precise focus under the weight of a full imaging train
- 60mm image circle keeps medium-format sensors fully illuminated at high magnification
- Retractable dew shield protects the front element through extended high-power sessions
- Heavy-duty flight case is built for transporting the heaviest tube in this product line safely
- Useful magnification tops out at 400x, with a practical floor of 29x
The APM CNC-LW II 203/1800 Advantage
Where the 1420mm version in this series favors general deep-sky imaging on large-format sensors, the 1800mm tube here is built for a narrower job done exceptionally well: extreme-contrast visual observation and binary star research where every extra arcsecond of image scale counts. The trade-off is a 26.5kg tube and a 50kg mount requirement, so this is a fixed-observatory instrument more than a portable one.
Applications & Use Cases
Built for observatory-class extreme-contrast high-power visual observation, this refractor also handles binary star research and high-resolution planetary astrophotography.
- Observers focused on binary star measurement rather than wide-field deep-sky targets
- Fixed observatory setups with a mount rated for 50kg or more
APM Warranty & Support
The CNC-LW II 203/1800 carries a 2-Year Factory Warranty covering manufacturing defects on the optical tube and focuser assembly, handled directly through APM’s support channel.
APM CNC-LW II 203/1800 Refractor OTA Specs
| Brand | APM Telescopes |
| Full Model Code | APM-LZOS-203/1800-CNC |
| Country of Origin | Germany |
| Optical Design | Apochromatic Refractor (3-Element Air-Spaced Super ED Triplet) |
| Aperture | 203 mm (8 inches) |
| Focal Length | 1800 mm |
| Focal Ratio | f/8.8 |
| Optical Coatings | Broadband Multi-Coated (99.6% Transmission per lens surface) |
| Secondary Mirror Obstruction | 0 mm (0%) |
| Secondary Mirror Obstruction by Area | 0% |
| Backfocus Distance | 220 mm from end of extension tube |
| Rear Cell Thread Type | M82x1 Indexing Thread / M68x1 Internal Thread |
| Image Circle Diameter | 60 mm (Optimized Medium Format Tracking Coverage) |
| Resolving Power | 0.57 Arcseconds |
| Limiting Visual Magnitude | 13.5 |
| Highest Useful Magnification | 400x |
| Lowest Useful Magnification | 29x |
| Optical Tube Material | Aluminum (CNC-LW II structural execution) |
| Focuser Style & Mechanism | 3.5-inch Starlight Instruments Feathertouch Dual-Speed Rack and Pinion Focuser |
| Mirror Lock Mechanism | No (Refractor Tube Configuration) |
| Optical Tube Dimensions | 250 mm x 1700 mm (transport length with retracted dew shield) |
| Optical Tube Weight | 26.5 kg (58.4 lbs) |
| Mount Attachment Type | Losmandy D-Style Dovetail Plate with heavy-duty CNC tube rings |
| Finder Scope Specification | Not Included (Mounting base bracket integrated) |
| Included Accessories | CNC Tube Rings, Retractable Dew Shield, 3.5-inch Feathertouch Focuser, Heavy-Duty Flight Case |
| Power Requirements | None |
| Standard Warranty | 2-Year Factory Warranty |
| Application | Observatory-class extreme contrast high-power visual observation, binary star research, and high-resolution planetary astrophotography, requiring a heavy-duty equatorial mount with a minimum payload capacity of 50 kg. |
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