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Askar 131F 0.74× Reducer
The Askar 131F 0.74x Reducer converts the Askar 131F refractor into a faster f/5.6 astrograph with a final focal length of 733.6mm. This dedicated triplet reducer provides a wider field of view and significantly shortens exposure times, all while maintaining a precise 55mm back focus distance and weighing just 0.56kg.
0.74x Reduction: Transforming the 131F to an f/5.6 Astrograph
By reducing the native f/7.5 optics of the Askar 131F to a faster f/5.6, this reducer cuts required exposure times by nearly half. This speed is critical for capturing faint details in nebulae and galaxies. The triplet optical design doesn't just reduce the focal length to 733.6mm; it also flattens the field, ensuring stars remain sharp and round across a full-frame sensor from the center to the corners of your image.
Mechanical Design: 55mm Back Focus and Full-Frame Correction
Engineered for seamless integration, the reducer maintains the industry-standard 55mm back focus distance, measured from the base of its M48 male thread. This simplifies the process of connecting your DSLR, mirrorless, or dedicated astronomy camera with standard adapters and off-axis guiders. The main body features a rear-end M72x1 thread for a secure connection to the telescope's focuser, and the CNC-machined housing ensures precise optical alignment.
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What does the Askar 131F 0.74× Reducer do to my telescope's focal length?
The 0.74x Reducer shortens the Askar 131F's native focal length to 733.6mm and speeds up the focal ratio from f/7.5 to f/5.6. This provides a wider field of view and gathers light more quickly, reducing your total imaging time.
What is the back focus of the Askar 131F 0.74× Reducer?
The required back focus is 55mm, measured from the base of the male M48 thread on the reducer. This is a standard distance that works directly with most DSLR cameras using a T-ring and many dedicated astronomy camera setups.
How will the Askar 131F 0.74× Reducer help me image the Andromeda Galaxy (M31)?
The Andromeda Galaxy is a very large target. The reducer's 733.6mm focal length provides a wider field of view, allowing you to capture the entire galaxy and its faint outer arms within a single frame using a full-frame or APS-C sensor. The faster f/5.6 optics will also help you capture more signal in less time.
Is the Askar 131F 0.74× Reducer suitable for imaging large nebulae like the North American Nebula (NGC 7000)?
Absolutely. The wide field of view provided by the 733.6mm focal length is ideal for framing large emission nebulae like NGC 7000. Furthermore, the fast f/5.6 focal ratio is highly effective at capturing faint hydrogen-alpha signal, making it a perfect match for such targets.
What kind of optical correction does the Askar 131F 0.74× Reducer provide?
The reducer uses a triplet lens design. This multi-element configuration is engineered not only to reduce the focal length but also to act as a field flattener, correcting for the natural field curvature of the main optics. This ensures that stars are sharp across the entire imaging sensor.
How much does the Askar 131F 0.74× Reducer weigh?
The reducer weighs 0.56kg. This is an important consideration for ensuring your mount remains properly balanced after adding the reducer and camera to the optical train.
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| Reduction Factor |
0.74x |
| Reduced Focal Length |
733.6mm |
| Reduced Focal Ratio |
f/5.6 |
| Lens Design |
Triplet |
| Back Focus |
55mm (from the base of M48 male thread) |
| Weight |
0.56kg |
| Rear-end Thread |
M72x1 |
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Askar 1-Year Warranty
