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The HoTech laser collimator with its patented self-centring adapter (SCA) mechanism enables precise, repeatable results.
Note 1: Prior to using a laser you will need to first check/set a Newtonian telescope's secondary mirror using a sight-tube. Fortunately once set it rarely needs further adjustment.
Note 2: For any laser collimator to be effective it needs to be fitted to a well-made focuser. The regular rack-and-pinion style focuser fitted to many beginner/intermediate telescopes lacks precision and rigidity. If in doubt please contact us for advice.
The SCA mechanism serves three critical functions: It's expansion rings accommodate almost all focuser's manufacturing tolerances. It automatically centres the adapting laser and provides at least two evenly distributed circular contacts on the focuser's inner tube surface preventing the laser from pivoting. Once the 'slop' factor is removed you can quickly and precisely collimate your telescope with confidence.
With Hotech's proprietary laser crosshair you can zero-in the laser with ease during the final collimation on the secondary and primary mirror. The crosshair model displays a precision laser centre dot with four extended laser lines for easier and more intuitive centering.
During the secondary mirror collimation, a single dot laser projecting on the approximate center of the pre-loaded donut can be difficult to identify if the laser dot is exactly on the center. The crosshair laser can easily help user to adjust the secondary mirror to point the laser on the exact centre with the help of the crosshair line. During the final primary mirror collimation the returning laser dot often hides inside the laser exiting hole when centred whereas the crosshair is visible at all times.
Collimation for your SCT
Traditional laser collimators are not suitable for collimating SCT telescopes but the Hotech laser's SCA mechanism and detailed faceplate provide the accuracy and repeatability necessary for even SCT collimation.
Commercially made SCT telescopes all have slight optical and mechanical alignment errors. The error typically is in the centreing of the secondary mirror. Consequently, when a laser is installed its beam will seldom return dead-centre, even though star testing might indicate perfect collimation. In addition, the secondary mirrors convex shape magnifies any error by approx 5 times. Typically a well collimated SCT will return a laser beam at around 0.125" to 0.250" off centre. In order to compensate a different approach is required than when collimating a Newtonian:
An SCT primary mirror is fixed but you can collimate by adjusting the secondary mirror to a point parallel to the optical axis. There is a one-time-only preparation required for SCT laser collimation. First, after a star collimation (still the most accurate method) install the SCA laser collimator then mark the laser spot position on the target grid of the collimator. Then, when you next check for collimation, look to see whether the laser spot falls on the mark. If not, adjust the alignment screws on the secondary mirror to move the returning laser dot to the mark. At this point you will have set the telescope's collimation back to a known position. Job done!
The 2" model is the 1.25" SCA laser collimator supplied with a SCA 1.25"-2" adapter.