How do I identify sensor tilt that the M68-Tilter can fix?
You can identify sensor tilt by examining a well-focused image of a dense star field. If stars in the center of the frame are sharp and round, but stars in one or two corners appear elongated or out-of-focus, you likely have tilt. The M68-Tilter is designed to correct this specific aberration by physically adjusting the sensor's angle relative to the optical axis.
Is the M68-Tilter suitable for my imaging setup with a full-frame camera and an f/4 reflector?
Yes, absolutely. Fast optical systems like an f/4 reflector are extremely sensitive to any misalignment, making tilt a common problem. The M68 thread standard is ideal for full-frame sensors, as it provides a large clear aperture that prevents vignetting, ensuring your entire sensor receives an unobstructed cone of light.
How is the M68-Tilter adjusted?
Adjustment is an iterative process that involves taking short test exposures and making small corrections between them. You would typically use a star analysis tool in your imaging software, or careful visual inspection, to check for improvements in corner star shape after each adjustment until the entire field is sharp.
Does using the M68-Tilter change my backfocus?
Yes. The tilter itself occupies physical space in your imaging train. You must account for its optical length, which is 9.5 mm at 0° tilt and increases to 10.25 mm at 1° tilt, in your overall backfocus calculation. Minor focus adjustments will be necessary after correcting for tilt.
Why choose an M68-Tilter over a smaller M48 or M54 version?
The M68 thread provides a significantly larger clear aperture compared to M48 (48mm) or M54 (54mm) threads. This is essential for preventing vignetting (darkening of the corners) on large sensors, such as full-frame (36x24mm) or medium format, ensuring even illumination across the entire imaging chip.
Why does the optical length of the M68-Tilter vary from 9.5 mm to 10.25 mm?
The base optical length is 9.5 mm when the tilter plates are perfectly parallel (at 0° of tilt). As you introduce an angle to correct the image plane, one side of the plate separates slightly more than the other. This increases the overall optical length, reaching a maximum of 10.25 mm when the unit is at its full 1° of tilt.
