What is the primary function of the T-2 Tilter?
The T-2 Tilter is designed to correct for field tilt, a common issue in astrophotography where the camera sensor is not perfectly perpendicular to the light path. This misalignment causes stars in one or more corners of the image to appear elongated or out of focus while the center remains sharp. The tilter allows you to make fine angular adjustments to square the sensor to the optical axis, ensuring sharp stars across the entire frame.
Where should I place the T-2 Tilter in my imaging setup?
For best results, the T-2 Tilter should be placed as close to the camera sensor as possible. The ideal location is typically right before the camera body, after any filter wheels, filter drawers, or off-axis guiders. This ensures that you are adjusting the camera sensor itself relative to the corrected optical path.
Is the T-2 Tilter necessary for my 8" f/10 SCT?
While any system can exhibit tilt, it is most pronounced in "fast" optical systems (typically f/5.5 or faster). An f/10 Schmidt-Cassegrain has a more forgiving depth of focus, so minor tilt may not be visible. However, if you are using a focal reducer that brings your system to f/7 or f/6.3, or if you notice persistent, one-sided star elongation, the T-2 Tilter can be a valuable tool for achieving perfect correction.
How do I know how much to adjust the T-2 Tilter?
Adjusting a tilter is an iterative process. You start by taking a short exposure of a dense star field. Analyze the image to see which corner or edge has the most elongated stars. You then make a small adjustment to the tilter to "push" the sensor plane in that direction. Take another test image and repeat the process until stars are uniformly round across the entire field. Software tools like N.I.N.A.'s Aberration Inspector can make this process much faster.
Will the T-2 Tilter correct for coma or field curvature?
No. The T-2 Tilter is a mechanical adjuster and corrects only for sensor tilt. It does not correct for optical aberrations like coma (common in Newtonians) or field curvature (common in refractors and SCTs). For those issues, you need a dedicated optical corrector, such as a coma corrector or a field flattener.
Will the T-2 Tilter add significant length to my imaging train?
While any component adds some length, tilters are generally designed to be as thin as possible to minimize their impact on back focus. You must account for its optical path length when calculating your back focus spacing, especially when used with a reducer or flattener that has a strict back focus requirement.
