Description
Starfield Adjustable 0.8x Reducer/Flattener (2") — Faster Imaging, Cleaner Corners, Easier Spacing
The Starfield 0.8x Adjustable Reducer/Flattener is built for refractor astrophotography when you want the benefits of a reducer (wider field + faster system) without fighting spacer rings. Set your back focus by dialing the reducer, then fine-tune with a small twist if needed.
This reducer/flattener is specified for illumination and correction up to 42mm sensor diameter (usable up to full-frame size), and is designed as a corrector + reducer for refractors.
Best for: imagers using filter wheels, rotators, and other accessories who still need to hit required back focus— without building a spacer tower.
Why an Adjustable Reducer Matters
- 0.8x reduction for a wider field of view and faster imaging workflow.
- Stepless spacing adjustment makes it easier to reach back focus, even with accessories in the train.
- Filters can be added inside the reducer for a compact, clean optical path.
Manual (Recommended)
For the full spacing workflow (including how to calculate your reducer setting with your exact camera train), use the official PDF manual: Starfield Reducer & Flattener Manual (PDF) .
Compatibility & Target Spacing (As Listed)
This reducer is shown as attaching directly to the Géar series focuser by removing the 2" adapter, then threading the reducer onto the focuser. The listing also notes it can be used on other telescopes and provides target values by aperture/focal ratio.
| Telescope | Target value (mm) |
|---|---|
| 102mm / f/7 | 55 |
| 90mm / f/6 | 56 |
| 80mm / f/7 | 57.6 |
| 80mm / f/6 | 59.6 |
| 70mm / f/6 | 61.6 |
Important: If you’re pairing with a non-Géar focuser/telescope, confirm thread interface and spacing using the manual before ordering.
Installation Summary (Quick)
- If a 2" visual adapter is installed, remove it first.
- Using the supplied 1.5mm Allen key, loosen the three locking screws about a half turn.
- Unscrew and remove the locking ring.
- Thread the reducer onto the focuser (M63 connection).
- Set spacing using the official manual: Open the manual (PDF) .
Technical Specifications
- Design: Corrector and reducer for refractor telescopes
- Reduction factor: 0.8x
- Optics: 3 lenses with ED element
- Coatings: Multi-coating and internal blackening
- Telescope connection: M63x1 external thread (male)
- Camera connection: M48x0.75 external thread (male)
- Working distance: Variable (adjustable)
- Adjustment range: 0–17 mm, stepless
- Sensor coverage claim: Illumination/correction up to 42mm sensor diameter (usable up to full-frame size)
- Filters: Filters can be added inside the reducer
- Suitable for (this product): Refractor telescopes 70–102 mm aperture (Small Reducer class)
FAQ
Is this reducer also a field flattener?
Yes—this product is described as a reducer and flattener (corrector/reducer) for refractor telescopes.
Do I need exactly 55mm back focus?
The listing emphasizes making 55mm back focus easy and also provides telescope-specific target values in the table. Follow the manual’s setup method for your imaging train.
Can I use it with a filter wheel and rotator?
Yes—this product is positioned for imaging trains that include accessories such as filter wheels and rotators while still reaching the required back focus.
What telescopes does it attach to?
The listing states it attaches directly to the Géar series telescopes focuser by removing the 2" accessory adapter, then threading on. For other telescopes, confirm threads and spacing using the manual.