เลนส์ถ่ายดาว Askar FMA230 50mm f/5.5 Triplet Apo Lens / Guidescope #FMA230

The ASKAR FMA230 is a premium multi-functional optical instrument that features a 50mm ED fully multicoated triplet objective to deliver superb image quality. It works at f/5.5 as a finder/small telescope/guide scope. It can also be easily configured as a seven-element f/4.6 apochromatic refractor/camera lens, making it an ideal instrument for serious wide-field astronomical or terrestrial imaging.

The heart of the FMA230 is an air-spaced 50mm apochromatic f/5.5 triplet with two ED elements to minimize chromatic aberration. The optics are fully multi-coated and the tube is internally blackened to ensure high contrast and minimal reflections.

With a focal length of 275 mm, the objective lens is optimized and tested for demanding astronomical applications. The objective is carefully matched to the included four-element 0.84x focal reducer that transforms the overall focal ratio to f/4.6 and a focal length of 230 mm.

For the price, this fast apochromatic lens offers excellent value and can approach the performance of telescopes that cost three or four times as much. This is especially true when matched with astronomy cameras with smaller 1" and 4/3" sensors. Cameras with larger APS-C and full-frame sensors may reveal slight aberrations at the edge of the field, especially when using the focal reducer.

With the included focuser ring and extension tubes, the FMA230 is easily configured for visual or photographic use. For visual observing, it includes a 2” adapter that accepts eyepieces or star diagonals (sold separately). For observing with a 1.25” diagonal, the scope includes a small extension tube to ensure focus (NOTE: A 2”-to-1.25” adapter is not included with the FMA230).

When configured for imaging with the focal reducer, the telescope side of the extension tube terminates in a standard M48x0.75 male T-thread for mating to a wide camera T-ring adapter (not included). The back focus is a standard 55mm. When the reducer is removed, the extension tube terminates with a female M62x0.75 thread. Imaging with the scope without the reducer will require you to use it in the "visual mode" with the included 2" adapter and the addtion of other spacers/adapters to reach focus (not included).

The Askar FMA230 also includes a set of red anodized aluminum tube rings and a Vixen dovetail mounting plate. The rings and plate allow for easy attachment of larger astronomy cameras and DSLR and mirrorless cameras.

The FMA230 also comes with an attractive carrying handle that doubles as a mount for finders, guide scopes, and an ASIAIR-PRO controller (all sold separately). The top of the handle is machined as an Arca-Swiss tripod plate, allowing you to ‘invert’ the scope and mount it easily on a photo tripod. The mounting rings, Vixen plate, and handle can also be completely removed when it’s used with a DSLR or mirrorless camera for handheld shooting or when the camera itself is mounted to a tripod.

The overall tube length of the FMA230 is 248 mm with the focal reducer installed and 221 mm without a reducer or star diagonal. The FMA230 weighs 1045 g (2.36 lbs).

Specifications:

• Aperture: 50mm
• Focal Length: 275mm (230mm with focal reducer installed)
• Focus Ratio: f/5.5 (f/4.6 with focal reducer installed)
• Objective Type:
• Triplet Dual ED Air-spaced APO (Objective lens)
• Septuplet Refractor for full-frame astrophotography (with reducer)
• Overall length:
• 221mm (photographic mode with focal reducer)
• 248mm (observation mode without star diagonal)
• Helical focuser travel: 30mm
• Weight: 1.1 kg (2.4 lbs.)
• Back-end Adapter:
• M48x0.75 (photographic mode)
• 2" Adapter (for visual observation mode)
• Included: 
• FMA230 Body
• Pair of tube rings
• Vixen dovetail plate
• Carrying handle/Guidescope Mount
• 2" Eyepiece Adapter
• Manual