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"It is incredible that most
telescope owners are unaware that their instruments are not properly
collimated. A properly collimated telescope will soar. With mine, M42's four
trapezium stars turn to six, and the red and green hues become more
prominent. Your collimator makes this essential task easy and fun. . . I
especially find the diffractive optic, which projects a grid pattern around
the beam, a useful addition. I recommend your collimator highly."
Howie Glatter produces some of the finest laser collimators available today. Howie Glatter's Laser Collimators are precision machined to fit your focuser perfectly. Even the Laser itself is tuned to a higher brightness than others. The Glatter holographic collimator has in addition to the laser, a removable transparent diffractive optic (the "hologram") that is placed in the path of the beam, just ahead of the laser. It diffracts light from the laser to project a diverging, symmetrical pattern around the beam, which is quite useful for centering optical elements and other procedures. The grid covers a wider angular range (21 degrees) than any other holographic collimator which allows direct centering of f/ 2.7 to f/ 35 optics. A rectilinear grid pattern gives the highest accuracy and sensitivity for centering circular optics of arbitrary size.
The most important specifications for a laser collimator are the accuracy and stability of the laser beam alignment to the cylindrical axis of the collimator body. Glatter's alignment tolerance is fifteen arc seconds for single beam mode, and one arc minute for the holographic mode. In order to ensure maintenance of this level of accuracy each of these collimators are engineered and then tested for resistance to shock.
The Blug (tm) is a new collimation product, used in conjunction with a regular laser collimator in single beam mode, to perform the Barlowed laser primary mirror alignment technique of Nils Olof Carlin (BLUG stands for Barlow plug). It has a matte-white 45 degree face as a screen, and a Barlow lens installed in a central axial hole. The BLUG is inserted in the inner end of the focuser drawtube, inside the tube or upper cage, and is retained by compression of an o-ring in a groove in the Blug base. The 45 degree white face of the Blug is easily visible from primary adjustment position on a truss DOB, or with a solid tube, if the BLUG face can be seen through the space between the primary and tube wall. With a solid tube scope the BLUG can be turned 180 degrees to face the front so the Barlowed shadow can be seen easily from the front of the scope. The Blug is sized to the drawtube, not to the collimator. For example, a 1 1/4" collimator with a 1 1/4" to 2" adapter could be used with a 2" Blug.
Read the review and discussion threads on the BLUG on Astromart at http://www.astromart.com/articles/article.asp?article_id=450
BARLOWED LASER PRIMARY ADJUSTMENT
Normally, a telescope takes parallel light rays from a distant star and converges them to a point at the eyepiece focus. Barlowed laser collimation takes advantage of the fact that a telescope will work in reverse. Placing a collimator into a barlow lens will cause the parallel rays of laser light to diverge, apparently from a point just behind the Barlow lens. The diverging rays projected from the laser-Barlow combination in the focuser are turned into a beam of all-parallel rays when they are reflected from the primary, except for where the center mark on the primary prevents the mirror from reflecting. This reflected beam, containing a superimposed shadow of the collimation target, is projected up to the secondary, and then reflected to the focuser.
If you placed your laser collimator into a conventional barlow lens, you need to attach a paper circle to the end of the barlow as a screen to view the shadow on. The paper circle needs to have a hole in it's center to pass the outgoing beam.
The primary tilt is now adjusted to center the target shadow around the hole. The position of the shadow on the screen is effected very little by motion of the illuminating beam. It is almost startling to see the shadow remain stationary as you "bend" the collimator and Barlow around in the focuser, and the fuzzy perimeter of the diverged laser beam moves all over the place.
A Barlowed collimator has a Barlow attachment that attaches to the laser aperture or to the focuser tube for making the primary adjustment. The Barlow attachment is a disc with a small barlow lens mounted in it's center hole, and a flat white front surface as a screen. It makes the Barlow procedure more compact and convenient. Great Red Spot stocks both types of Barlowed targets for the Glatter collimators.
Read the entire article on collimating with a barlowed laser by going to http://gmpexpress.net/~tomhole/blaser.pdf#search='collimating%20with%20a%20barlowed%20laser and downloading the PDF article.
The BLUG, TuBlug, and FLUG