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Hotech 2" SCA Dot Laser Collimator - SCA-2D


Hotech 2" SCA Laser Dot Collimator

The HoTech 2" SCA Laser Collimator works with 2" focusers. The HoTech laser collimator separates itself from all the other laser collimators with its innovative self-centering adapter technology (SCA). The mechanism allows precise and repeatable installation in all brands of 2" telescope focusers. All laser collimators in the current market have one fundamental problem: the slop in the adapting mechanism between the laser collimator and the telescope focuser. This problem is clearly recognized and often discussed among astronomers.

No matter how tight the tolerances are machined on the laser collimator or the focuser, a small gap is required to allow installation of the laser collimator. Once the laser collimator is inserted, the required gap becomes a problem. The laser collimator is fixed either with one or more thumbscrews or an unified compression ring. Both methods introduce a very critical issue, namely an off-axis installation that instantly destroys the precision of your collimation instrument along the entire optical axis.

The HoTech Self-Centering Adapter cleverly eliminates the slop by linearly compressing the built-in rubber rings. By doing this, the diameter of the rings expands to compensate the gap. Because all rings evenly expand radially in diameter from the compression, this automatically centers the laser collimator in the focuser draw tube. The SCA adapter accommodates various brands of adapting focusers which have slightly different manufacturing inside diameters, so this laser collimator will be precisely centered for each installment. The HoTech SCA adapter serves three critical functions. First, its expansion rings accommodate almost all focuser's manufacturing tolerances. Second, it automatically centers the adapting laser. Third, it provides at least two evenly distributed circular contacts on the focuser's inner tube surface preventing the adapting laser from pivoting.

Commercially made SCTs all have slight optical and mechanical alignment errors. The error typically is in the centering of the secondary mirror. As the result, when a laser is installed and emitted from the focuser, the beam will seldom return dead center, even though star testing would indicate perfect collimation. In addition, the secondary mirror, convex shape, magnifies any error by about 5 times. The error of deviation for a typical well collimated SCT will return laser beam at around 0.125" to 0.250" off center. In order to compensate the optical and mechanical alignment errors of SCT, a different collimation approach is required in compare with Newtonain telescope. If the procedure is followed through correctly, users can still accurately collimate their SCT.

By default, the laser will have to be positioned in the optical center of the SCT. HoTech SCA laser collimators automatically eliminate the focuser slop without using the thumbscrew and center position itself on optical axis. In an SCT, the primary mirror is fixed, but you can still collimate the SCT by adjusting the secondary mirror to point parallel to the optical axis.

There is a preparation step you need to do for SCT laser collimation. First, install the SCA laser collimator and premark the laser position on the target grid of the collimator when your telescope is collimated from the factory or from your star collimation. Then when you check for collimation next time, just adapt the SCA laser collimator on the focuser, 2" or 1.25" and see if the laser falls on the premarked laser position. If not, adjust the alignment screws on the secondary mirror to move the returning laser dot to the premarked postion on the target grid.

Hotech 2" SCA Laser Collimator Features:

  • Precision Machined Compact Lightweight Design: Many laser collimator manufacturers give users the wrong impression, "big and heavy means rugged and stable." Instead, HoTech engineers successfully cut the unnecessary weight on the laser collimator because they understand that additional weight on a telescope (especially open structure Newtonians) will create imbalance and structure sagging. In addition, the heavier the device is, the more inertia it will have during an impact from an accidental drop. In such an accident, the inertia force can cause more damage to the internal alignment mechanism because there is more energy required to dissipate from the impact. Therefore, the lightweight design on the HoTech laser collimator makes you gain reliable precision collimation. And of course their laser collimator uses aero-space grade lightweight aluminum material and CNC machined with the tightest tolerances, then sand blasted and anodized to protect from harsh environment. Nothing has been sacrificed while you get a long lasting state-of-the-art collimation instrument.
  • Includes 45 degree Faceplate Viewer with Laser Engraved Targeting Grid: The faceplate viewer helps to display the returning laser spot with a clear visual reference during adjustment. The faceplate allows alignment of the primary mirror from the rear of the telescope eliminating traveling to the front of the scope repeatedly during collimation. HoTech understands the importance of this, so the faceplate is a standard feature in their laser collimator. In addition, the faceplate viewer's pattern is laser engraved to ensure a long lasting sharp targeting grid. Unlike other collimators, the target is not a sticker that will peel, or paint that can rub off or chip.
  • Finest Projecting Laser Dot: Keeping the laser dot to the finest point is the key to precision collimation. But when you look closely at the laser dot from brand to brand, most laser dots appear large, not really a fine point as you imagined. This means there is guess work involved when you try to center the dot; not just centering the laser dot to the center of the faceplate, but also centering the center of the dot itself. This does not make any sense when you are trying to take the advantage of the collimated laser beam's characteristic "which has a low beam divergence, so that the beam radius does not undergo significant changes within moderate propagation distances." In other words, the laser beam size within the collimation distance (laser collimator to the primary mirror and back to the faceplate) should remain a constant fine point. As you know, most laser collimator brands are not really laser manufacturers. They install an off-the-shelf laser module or pointer and align the laser in a tube without REALLY considering the user's application, namely the operating distance for a laser beam size. HoTech has been designing and building laser modules and systems for over 10 years for various professional industries. They know exactly how a laser should work. HoTech limits their laser beam to the finest size in the correct operating distance for optimal effect. Their understanding and experiences with the laser design permit you to have an effective and precision collimation.
  • High Accuracy Laser Alignment.The HoTech laser collimator is well centered and aligned which are critical factors for an accurate collimation. But you will be surprised that many laser collimators in the market fail in this regard. The reason is in the design and understanding of the product itself. HoTech has considered all aspects of parameters in their design. Parameters like the alignment mechanism, mechanical and optical structure of the laser itself, and more, are taken as part of the design. For instance, some laser collimators actually install an off-the-shelf laser pointer in the casing. It is very cost effective (for seller), but it inherits numerous problems. In many cases, the laser pointer might not install perfectly centered in the casing due to pointer size variations and the added alignment mechanism. So the laser itself is not positioned on the true alignment point and optical axis. As the result, the laser can never be center-aligned in the enclosure. It is possible to align the laser beam parallel to the optical path but always with an offset along the optical axis. This means the laser beam is off no matter how you center adapt the laser collimator to the focuser.
  • Long Lasting Battery Life: By using the CR123, 3V battery as the laser power source, the HoTech laser collimator has over 65 hours of continuous use battery life time. The included CR123, 3V lithium battery operates well under a typical cold night and it has a 10 years shelf life. This is a great advantage that you don't have to worry about changing the tiny hard to find cell batteries frequently in the dark like other collimators.