Home >> Science & Nature >> Astronomy

What Is a Telescope Light Box?

A light box is an attachment, placed in front of a telescope, to diffuse the light entering the telescope. The light box diffuses the light from target objects, creating a flat field frame to produce a more evenly lit image. Unevenness of light from the source and optical imperfections in the optical train are reduced or removed by the light box in order to allow higher quality astrophotography. Photographs taken through a light box do not suffer from the same vignetting effects and reflections as those taken without one.

Construction of a Light Box
- A light box should be made of lightweight yet sturdy material such as foam board. A hole is cut at one end of the box to receive light from target objects. The other end of the box may feature a hole to accept the telescope, or the interior dimensions of the box may be fitted to the outside of the telescope to hold it in place. One or more diffusers are attached inside of the box, between the telescope's end and the hole which receives light. The diffuser is made of drafting vellum or another light-diffusing material, and it is held in place by a frame attached to the interior of the box.
How Light Boxes Work
- The diffusers in a light box allow digital cameras and imaging software to identify any uneven lighting in an image, then compensate by subtracting it digitally to create a flat, even image. The camera essentially takes a photograph of the diffused image created by the light box, rather than the direct image of the target object, and imaging software adjusts the final image.
Light Box Benefits
- A light box provides a constant light level, which is not affected by reflections from external surfaces or light sources. Because of this consistency, imaging quality can be expected to remain constant and reliable. Other methods of light diffusion or correction, such as sky flats, require time and some calibration to set up for optimal performance. Light boxes, however, simply slide on and off of the telescope's dew cap. This makes setting them up a quick and easy process by comparison.
Light Box Sizing
- Light box dimensions and construction are not dictated by a universal set of standards. Rather, a light box must simply conform to the dimensions of its respective telescope and the needs of the photography equipment being used. The interior space of a light box should be fitted to the outside diameter of the telescope on which it is used. The hole that accepts light from the target needs only to match the usable inside aperture diameter that the camera captures when attached to the telescope.

Astronomy