Hotech 2" SCA Field Flattener

Hotech SCA Field Flattener 2"

The image plane of most refractor telescopes is not flat, but camera sensors are. This makes it impossible to get an evenly sharp image over the whole field. Slight differences of instruments with long focal lengths cannot be seen if the photograph was made on film with its limited resolution, but these instruments are barely used today. With modern telescopes and modern digital cameras, it becomes necessary to flatten the image plane.

The SCA Field Flattener is designed for this purpose. It is suitable for refractors with focal ratios from f/8 to f/5 and, if the optics itself is good, you will see bright and sharp image across the entire field.

Many flatteners will change the focal length of the system, but with this one from Hotech, it will stay the same.

The Self-Centering Adapter (SCA) mechanism brings your camera to the closest optical axis in the drawtube/visual back for BEST imaging result
To capture great images from your telescope, it is essential to position your camera firmly in and on the optical axis of your drawtube/visual back. The SCA T-Adapter center loads your camera in the drawtube/visual back with a simple threading of a compression ring forcing the built-in rubber rings outward radially, thereby centering the camera in the drawtube/visual back for optimal installation.

SCA eliminates drawtube/visual back slop
All drawtubes / visual backs have manufacturing tolerances. And it requires larger diameter to accept various eyepieces and adapters. When the camera adapter is inserted, the gap between the drawtube/visual back and the inserted device becomes a slop problem. The rubber rings in the SCA, on the other hand, expand radially according to users own adjustment to fill the gap. This makes your camera seats firmly in your drawtube/visual back becoming part of your telescope for a secure and repeatable installation.

SCA eliminates unstable locking from thumbscrew or unified compression ring
The optical axis is shifted when the inserting device is locked in by thumbscrew. In some cases, some poorly made unified compression ring can cause unstable tilt when locking in the drawtube due to loose tolerances between the compression ring, inner groove, and the uneven tip of the locking thumbscrew in a drawtube. The SCA T-Adapter connects your camera without using the thumbscrew or the unified compression ring, so the problem does not occure here.

SCA accepts the imperfection of a drawtube/visual back
Small imperfection inside the drawtube like dents and scratches, the rubber rings fill the gaps and faithfully centers your camera in the tube. In addition, even if the drawtube is slightly deformed in diameter, egg-shape, the rubber rings in the SCA will compensate the differences and faithfully centers your camera.

Short SCA profile prevents oscillation
Short profile design keeps the installed camera stable from low frequency oscillation transferred from the telescope in a windy environment. The non-reducer flattener´s back focuse distance, T-Thread shoulder to the CCD chip, requirement is 55 mm.

SCA damps vibration
The all-around adjustable tightness rubber contact damps unwanted vibrations from the telescope and provides a sturdy attachment on your telescope for a stable image capture.

SCA provides repeatable, reliable, and easy connection between your telescope and the camera.
The SCA T-Adapter fits any telescope that uses a 2" focuser or visual back. Use your existing T-Ring that matches your brand of camera and thread it onto the SCA T-Adapter. The T-ring thread accepts all kinds of 35 mm cameras - including both (D)SLRs and mirrorless system cameras. Of course, APS and smaller formats can also be used, allowing to deploy specialized astro cameras.

The 2" Field Flattener accepts 2" filter threads
SCA Field Flattener has built-in standard 2" / 48 mm (M48x0.75) filter thread.

Question:
How do you have to measure the working distance?

Answer from Teleskop-Service:
The working distance is measured from the beginning of the connection thread on the housing of the corrector (see example picture):

Safety informations: PDF Download