This 1.25” single beam laser collimator from Howie Glatter can be used for collimating almost any type of telescope, but has a separate concentric circle pattern hologram designed specifically for collimating Ritchey-Chrétien scopes.
Optics that are out of collimation (with optical elements that are not all exactly aligned on the same optical axis) cannot produce good images. Stars will be elongated or lopsided, planetary details will be hazy and low in contrast, and binary stars will be difficult to split cleanly. Regular collimation with this highly accurate laser collimator will make sure that you get the best possible image contrast and resolution every night you go out to observe.
Precisely centered inside this 1.25” Glatter Laser Collimator’s 3” long machined aluminum body is a solid-state 5 milliwatt laser diode. This emits an intense beam of red laser light exactly along the central axis of the cylindrical collimator body. A transparent removable diffractive optical element (the “hologram” generator module) is threaded into the body of the collimator, in front of the laser emitter, as seen in the main image above. This diffracts the single beam of light from the laser to project a diverging concentric circle pattern. This pattern is exceptionally useful for aligning and centering the hyperbolic mirrors of Ritchey-Chrétien optics. The concentric circle pattern can be seen in the feature image above.
Because there are some collimating situations in which the concentric ccircle pattern is unnecessary or unwanted (such as when collimating a Newtonian reflector or Dobsonian), the hologram generator module unscrews from the laser aperture and can be replaced by a single beam aperture insert with a white reflective collar.
The beam from all red diode lasers used in collimators is fuzzy-edged and elliptical in cross-section. When collimating, you sometimes must judge the location of the center of the spot by eye. To improve collimating precision, the single beam aperture insert has a 1mm hole surrounded by a matte white circular target. It produces a tiny, circular beam which allows more accurate alignment. With the single beam aperture threaded into the collimator, the beam impact on a flat surface at a distance of one meter or more looks like a star diffraction pattern, with a central dot surrounded by diffraction rings. The surrounding rings can help in centering the beam very accurately. When the single beam aperture is removed, the holographic generator module retains its alignment accuracy when it is screwed back into place in the collimator body.
The laser emits monochromatic red light at a wavelength of 635 nanometers. This wavelength appears two to three times brighter than the more common 650nm laser collimators, due to the human eye’s greater sensitivity to the shorter wavelength. This allows collimation under higher levels of ambient light, such as during twilight when first setting up your scope, so you don’t lose valuable observing time when darkness falls. A recessed push-button switch in the end of the body turns the laser on and off.
CAUTION: The Class IIIa laser in this collimator has a maximum output of 5 thousandths of a Watt (5 mw). This is quite safe if it is used with reasonable precautions. However, direct or mirror-reflected eye exposure should be avoided! Detectable eye damage can occur if the laser beam is focused on the same area of the retina for as little as 0.25 second. Therefore, take care when collimating your scope to be sure that the beam does not enter anyone’s eye directly, including your own. Keep it locked away when not in use and out of the hands of children. It is not a Star Wars light saber for them to play with.
There is no danger in viewing the beam’s impact on a surface that produces a diffuse reflection, such as the face of the laser collimator itself. The beam impact may also be safely viewed on a mirror or lens surface, if the reflected or transmitted beam is not directed towards your eye. A Newtonian or Cassegrain that is badly out of collimation may allow the beam to exit the front of the telescope, so when collimating these scopes, check first by pointing the telescope at a wall or screen to see if the beam is getting past the secondary or diagonal mirror. With a refractor, the beam will always exit the front of the telescope, so run a strip of masking tape across the diameter of the dew cap opening as a safety beam stop.
Two important considerations in choosing a laser collimator are the accuracy and stability of the laser beam alignment to the cylindrical axis of the collimator body. This collimator’s alignment tolerance is an impressive fifteen arc seconds. In order to ensure that this level of accuracy is always available, the collimator is designed – and tested – to withstand a shock equivalent to dropping the collimator from the eyepiece position on a tall Dobsonian telescope, without altering the fifteen arc second alignment. Most other laser collimators cannot withstand this kind of accident without loss of alignment.
The collimator comes with a single CR123A lithium battery that will power the laser for approximately 40 hours. Lithium batteries maintain a stable output voltage for their entire lifetime, giving maximum laser output. Replacement batteries are widely available (they are commonly used in point-and-shoot cameras) and usually sell for about $6-$7. The collimator is supplied with one battery, a plastic storage case, press-on collimation “donuts” for use with Newtonian reflectors, and very complete instructions for collimating telescopes of all optical types.