What is the primary function of the William Optics Flattener 68III?
The Flattener 68III is an optical corrector designed to eliminate field curvature in refractor telescopes. It ensures that stars are sharp and pinpoint not just in the center of the image, but all the way to the corners. As a 1.0x flattener, it accomplishes this without changing the telescope's native focal length or f-ratio.
Which telescopes is the Flattener 68III compatible with?
This flattener is specifically designed for a direct, threaded connection to the M92 focusers on the following William Optics models:
- Fluorostar 132 (FLT132)
- Gran Turismo 102 (GT102)
- Gran Turismo 153 (GT153)
How does the Flattener 68III perform with a full-frame camera like a Sony A7 on the GT102?
It's an excellent match. The Flattener 68III is designed to correct the entire field of a full-frame sensor. When paired with a GT102, you can expect sharp, round stars across the entire 24x36mm sensor of a Sony A7-series camera, with minimal vignetting thanks to the M48 camera connection.
Why should I choose this 1.0x Flattener 68III instead of a reducer/flattener?
Choose the 1.0x Flattener 68III when your primary goal is maximum image resolution and scale. A reducer/flattener makes your telescope "faster" and provides a wider field of view, but it shrinks the image. For detailed work on smaller galaxies or planetary nebulae where every bit of focal length matters, a 1.0x flattener is the superior choice.
What does the "adjustable" feature of the Flattener 68III do?
The adjustable design allows you to make micro-adjustments to the back focus distance—the spacing between the flattener's rear lens and your camera sensor. This is crucial for achieving perfect corner-to-corner star sharpness, as it lets you compensate for the exact thickness of your adapters, filter wheels, or off-axis guiders.
Will the Flattener 68III work for imaging the full Andromeda Galaxy (M31) with an FLT132?
While the Flattener 68III will provide a perfectly corrected field, an FLT132 at its native focal length may be too magnified to capture the entire Andromeda Galaxy (M31) in a single frame, even with a full-frame sensor. For a target of that size with that telescope, a reducer/flattener would be a better choice to achieve a wider field of view.
