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Asking Price
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Condition
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Distance from you
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$65.00
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New
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Description:
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Howie Glatter 2" BLUG
Great Red Spot Astronomy Products
www.greatredspot.com
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.
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/blase...39;collimating with a barlowed laser' and downloading the PDF article.
Read a review at http://www.rca-omsi.org/news/gazette_07/2007_05.pdf
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Keywords:
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Howie Glatter 2" Barlowed BLUG
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