Description
The Akar/Askar FRA 400/500 F3.9 Full Frame Reducer is a dedicated 0.7× focal reducer and field flattener designed for the Askar FRA400 and FRA500 astrographs. Its purpose is to make the telescope faster for astrophotography while maintaining a flat image circle suitable for full-frame cameras.
What it does
For the FRA400:
- Native: 400 mm focal length, f/5.6
- With reducer: 280 mm focal length, f/3.9
The 0.7× reduction widens the field of view and cuts exposure times significantly because the system gathers light more efficiently at f/3.9.
For the FRA500:
- Native: 500 mm focal length, f/5.6
- With reducer: 350 mm focal length, f/3.9
This makes it particularly attractive for large nebulae, dark nebula complexes, and wide-field galaxy groups.
Key features
- Designed specifically for the FRA400/FRA500 optical design.
- Supports full-frame sensors without needing an additional flattener.
- Maintains a corrected, flat field across a large image circle.
- Reduces exposure times compared with the native f/5.6 configuration.
- Uses a multi-element optical design optimized for imaging rather than visual use.
Advantages
| Benefit | Effect |
|---|---|
| Faster focal ratio | About 2× faster imaging than f/5.6 |
| Wider field of view | Larger nebulae fit in one frame |
| Full-frame correction | Suitable for cameras like Sony A7 series, Nikon Z, Canon R full-frame astro setups |
| Dedicated design | Better edge performance than generic reducers |
This Unit
This item is slightly used. It has been used a handful of times and shows no signs of use or abuse. This item is from my own personal items. I am just starting the experimental phase of hosting my used products on the website. Feel free to contact me at anthonydavoli@admaccessories.com or text 716-830-0413 to ask questions or make me an offer. Free Shipping.
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