DayStar Filters Interference Eliminator (T-Mount)

DayStar Filters Interference Eliminator (T-Mount)

Features

• Use for Solar Photography
• Limits Newton's Rings Interference
• Changes Angle of Incidence up to 5°
• Recommended for Long Focal Ratios
• Maximum Camera Weight: 7.7 lb

When photographing the sun in monochromatic light, such as H-alpha, a common issue is the appearance of lines on the resulting image caused by light reflection inside the DSLR camera's imaging sensor.

Daystar Filters' T-mount equipped Interference Eliminator tilts the camera off-normal by up to 5° while keeping the center of the image sensor stationary, so that focus, framing, and vignetting are not affected.

This tilt changes the angle of incidence and optical path lengths inside the image sensor, mitigating or eliminating the interference. These lines, called interference fringes, interference patterns, or Newton's Rings, are caused in long focal ratio applications, by nearly parallel light being internally reflected inside the image sensor or camera, causing an addition or subtraction of the light waves.

The Interference Eliminator can hold a camera rig up to 7.7 lb and is recommended for long focal ratios, f/30 ideally, as seen in most Daystar filters.

Installation & Use

Installation: The Interference Eliminator should be placed directly in front of the camera in the optical train. For proper operation, the distance from the flange of the male T thread to the camera focal plane should be 55mm. On a DSLR with a T ring, no spacers are required, the T ring sets the distance to 55mm. On a CCD camera or Webcam, male to female T ring spacers may be required to bring the distance to 55mm. If the distance is significantly different from 55mm, the camera will move off boresight and the focus position will shift while adjusting the Interference Eliminator tilt setting.

Use: Slightly loosen the thumbscrews and slide the two halves of the Interference Eliminator apart, such that the camera tilts. Take a few images with the camera to check for the interference pattern. Slide further apart if the pattern is still evident. Tilt it the minimum amount to eliminate fringes - too far and focus could be lost at the top and bottom of the image, especially in fast focal ratio systems. If maximum tilt is reached without satisfactory effect, try full tilt in the opposite direction. In some severe instances the interference pattern may not be completely removable, but it will be reduced to where other techniques such as flatfielding or compositing can make the image acceptable.

Notes: On large sensors such as full frame 36x24mm DSLR cameras, some vignetting is possible at full tilt due to the camera structure and the inside diameter of the T thread. For an example of a full frame Canon EOS 5D image at full tilt, click here. With webcams or 1.5-1.6x crop digital SLRs no vignetting will occur.