Description
Starfield Adjustable 0.8x Reducer/Flattener — Large Refractors, Faster Imaging, Easier Back Focus
The Starfield 0.8x Adjustable Reducer/Flattener (2.5") is designed to make accurate back focus easy on larger refractors—especially when your imaging train includes accessories like filter wheels and rotators. Instead of stacking spacer rings and guessing, you dial the adjustment and fine-tune with a small twist.
Manual (Recommended for Spacing & Setup)
This product is adjustable, and spacing depends on your exact camera train. For the complete setup workflow and spacing guidance, use the official PDF: Starfield Reducer & Flattener Manual (PDF) .
Why an Adjustable Reducer Matters (Beginner + Technical)
- 0.8x reduction gives a wider field of view and a faster imaging system.
- Adjustable back focus reduces the need for trial-and-error with spacer rings.
- Accessory-friendly: designed for imaging trains using filter wheels and rotators while still reaching required spacing.
- Cleaner mechanical stack: fewer stacked rings means fewer opportunities for tilt and flex.
Compatibility & Target Spacing (As Listed)
The reducer is described as attaching directly to the telescope focuser by removing the 2" adapter. The listing also notes it can be used on other manufacturers’ telescopes; a M63 to 2" push adapter might be required (contact us for details).
How to calculate your reducer setting (quick method)
The listing provides this method: add up the thickness of all accessories in your imaging train plus your camera sensor distance, then subtract from 69.87 and set the reducer to the calculated number.
Total back focus required by telescope model (table from the listing)
| Telescope | Target value (mm) |
|---|---|
| 102mm / f/7 | 69.87 |
| 107mm / f/6.5 | 69.0 |
| 130mm / f/7 | 66.17 |
| 140mm / f/6.5 | 65.8 |
| 150mm / f/8 | 63.34 |
| 155mm / f/8 | 62.57 |
Note: This reducer can also be used for other manufacture telescopes providing the focuser thread matches the reducer. Target values may be different for non-Starfield Optics telescopes.
Installation Summary (Quick)
- Using a 1.5mm Allen key, loosen the three screws about a half turn. (if present)
- Unscrew and remove the lock.
- Thread the reducer onto the focuser (M63 connection).
- Set your spacing using the 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
- Camera connection: M48x0.75 external thread
- Working distance: Variable (adjustable)
- Adjustment range: 0–17mm, stepless
- Filters: Filters can be added inside the reducer
- Suitable for: Refractor telescopes from 102mm to 155mm aperture with focusers from 2.5"
FAQ
Is this a reducer and a flattener?
Yes. This product is described as an adjustable reducer and flattener (corrector/reducer) for refractor telescopes.
What if I’m using a filter wheel or rotator?
This reducer is positioned specifically for imaging trains that include accessories such as filter wheels and rotators while still reaching required back focus.
Can it be used on non-Starfield telescopes?
Yes—the listing states it can be used on other manufacturers’ telescopes. A M63 to 2" push adapter might be required. Contact us if you’re unsure.