The TCA-4 is a very specialised photo adapter. It is designed for eyepiece projection photography of the Moon and planets.
The principle consists of photographing the image formed by an eyepiece with a CCD camera or a DSLR without lens. The advantage of this technique is that very high magnification ratios can be obtained, ideal for objects such as planets or the Moon. However, the image will appear less constrasted, due to the large eyepiece-to-sensor distance required. Finally, the use of an excellent quality eyepiece is strongly recommended to avoid degrading the image obtained.
The Takahashi TCA-4 Camera Adapter is composed of 2 removable elements: an eyepiece holder and a variable extension tube.
The eyepiece holder is designed to hold the projection eyepiece. The input side is M43x0.75 threaded. The output side is an eyepiece adapter with a 31.75 mm female barrel. The variable extension tube is attached to the eyepiece holder by means of a 50.8 mm female barrel. The output side is a male T thread (M42x0.75) which accepts standard T rings. It has a sliding device that allows the draw of the mount to be varied and therefore the magnification ratio on the sensor to be varied.
| Characteristic | Takahashi TCA-4 Camera Adapter |
| Item number | TKA00210 |
| Mechanical interface (input) | M43x0.75 thread, male |
| Mechanical interface (output) | M42x0.75 thread, male |
| Length | 110 mm |
| Weight | 320 g |
