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HoTech 2" SCA Field Flattener with T-Thread for f/5 - f/8 Refractor Telescope FF582

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High Quality Optics Designed for Refractor Telescopes! This field flattener is fully multi-coated on a two-element lens allowing the most efficient light transmission without sacrificing the precious light collected from your telescope. It accommodates f/5 to f/8 refractor telescopes. You will see bright and sharp images across the entire field.

The Field Flattener has built-in standard 2"/48mm (M48-P0.75) female filter thread on the telescope side. On the camera side is a male T-thread (M42x0.75) that accepts all kinds of 35mm cameras (Camera specific 42mm T-ring required for this is not included). Note that this T thread is not the same as the newer 48mm T thread found on a few adapters and accessories.

The flattener's back-focus requirement is 55mm (2.17") from the male T-thread to the CCD chip on your camera. This is to be measured from the shoulder of the flattener (where the male T thread begins). The length of the male T thread is approximately 2.5mm but this will be covered by the T thread spacer or T ring. Many T rings have a thickness of 16mm, of which 5mm will be inserted into the camera body, leaving an effective optical path length of 11mm for the T ring. So, for example, threading a T ring on this flattener will provide a spacing of 16mm from the shoulder of the flattener to the end of the T ring, or 11mm to the camera lens mount. With many of today's SLR cameras, a T ring might provide all the spacing you need with this flattener. T thread spacers are sold separately if you need additional spacing.

The image of Vega below was taken with a Takahashi TSA-102 (f/8) telescope using a Canon SXi DSLR. Stack of 4 x 5 min exposures without sharpening or noise reduction. Note that the enlarged star at the right edge of the photo remains circular.

SCA (Self Centering Adapter) Brings your Camera to the Closest Optical Axis in the Drawtube/Visual back for the 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 the 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 drawtube/visual backs have manufacturing tolerances and require a 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 creates a slop problem. The rubber rings in the SCA expand radially according to the users own adjustment to fill the gaps. This makes sure that 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 inserted device is locked in by the thumbscrew. In some cases, some poorly made unified compression rings 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 fits your camera without using the thumbscrew or the unified compression ring.

SCA Accepts the Imperfection of a Drawtube/Visual Back
Have small imperfections inside the drawtube like dents or scratches?  The rubber rings fill the gaps and faithfully center your camera in the tube. In addition, even if the drawtube is slightly deformed in diameter or egg-shaped, the rubber rings in the SCA will compensate for the difference and faithfully center your camera.

Short SCA Profile Prevents Oscillation
The short profile design keeps the installed camera stable from low frequency oscillation transferred from the telescope in a windy environment. The back focus of the 2" SCA T-Adapter is 19mm (0.75") measured from drawtube shoulder to the bottom T-Thread.

SCA Damps Vibration
The all-around, adjustable tightness, rubber contact dampens unwanted vibrations from the telescope providing you a sturdy attachment on your telescope for stable image capture.

Weight = 5.6oz.


Note: Occasionally, the product you receive might have a slightly different cosmetic appearance or labeling than what is shown. This can often change from batch to batch according to the whims of the manufacturer. However, you will always receive a brand new, original product as described above.

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Filed under: Eyepieces & Accessories