The dual sized Howie Glatter 1.25" and 2" collimator is ideal for people who own both focuser sizes. The Laser itself is tuned to a higher brightness than others. Each one comes with a 1mm Aperture Stop for a pin point laser dot. The 635nm laser is more expensive, but it enables Barlowed or holographic collimation in higher levels of ambient light. All of the collimators are powered by a CR123A lithium cell, giving about 40 hours of service. They come with one battery, a plastic case and collimation donuts.
In order to achieve the best possible resolution and contrast, the optical elements of a telescope must be put into near-perfect alignment. Collimation is the adjustment of the position and orientation of the optical elements to achieve best performance. Laser collimation is a relatively new way to accurately and precisely collimate a telescope.
When practiced with accurate tools and correct techniques the various methods of collimation will converge to the same result, but laser collimation has several unique advantages. The laser collimator provides its own light source, so collimation can be readily accomplished or checked after dark without additional equipment. Unlike passive collimation tools, your eye position is not constrained by a peep-hole and cross hairs, and you don’t need to scrutinize elements at different distances simultaneously.
Laser alignment and Shock Resistance
In use, the laser collimator is placed in the telescope’s eyepiece holder and clamped. A laser module inside the collimator emits an intense, thin, parallel beam of light, which exits a front aperture and projects along the central axis of the cylindrical collimator body. The beam acts as a reference line from which alignments are made.
The most important thing about a laser collimator is that the beam be aligned with the collimator's cylindrical axis. If the beam alignment with the collimator body is off, the collimation will be off and the telescope will not achieve its best performance.
For a collimator to serve as a reliable reference tool over the long term, the internal laser alignment must withstand mechanical shock. My collimators incorporate features to make them highly shock resistant. After I align the laser to the collimator body within 15 arc seconds, I test the collimator by whacking it against a block of urethane, striking at least a dozen times on three axis. I then check the alignment, and if it hasn’t changed the collimator goes into stock. The collimators usually withstand drops from eyepiece position up a ladder without losing alignment. I believe my collimators are unique in this respect.
If the laser in a collimator is misaligned, rotation of the collimator on its axis will cause the beam impact to trace a circle. However, rotating a collimator in an eyepiece holder is not the best test ofa collimator's alignment due to the small space between an eyepiece holder and the collimator. The collimator may precess like a top as it is rotated, and then even a good collimator's spot can travel in a circle. For a valid test the beam impact location should be carefully noted, then the collimator unclamped, rotated, and re-clamped, and the beam location checked to see if it has wandered.
I produce the collimators in three different body sizes: a 1¼" only, a 2" only, and a combination 2"-1¼" size. The combination size is 2" at the back, and steps down to 1¼"at the front. The 2"- 1¼" or 2" collimator is recommended for accurate alignment in a 2" eyepiece holder, but the 1¼" collimator is o.k. in a 2" holder if used with an accurate adapter bushing. The adapter can be itself checked for accuracy with the collimator by rotating the adapter and reclamping it, and seeing if the laser spot wanders.
The red collimators are offered with a choice of either 650 nanometer or 635nm wavelength. Both lasers have the same beam power output, but because the human eye's sensitivity to the shorter wavelength is greater, the 635nm. laser appears about two or three times brighter. The 635nm laser is more expensive, but it enables Barlowed or holographic collimation in higher levels of ambient light. In darkness the 650nm laser is adequate.
I also offer a 532nm green collimator, much brighter than the red ones. In most circumstances it is overly bright for night time collimation, but it is useful for Barlowed or holographic collimation daylight or room light. It is stocked in the 2"-1¼" combination size only.
The 1mm stop Attachment
The beam produced by red lasers used in collimators is fuzzy-edged and elongated. When making collimating adjustments you will have to judge the location of the center of the spot by eye. To improve adjustment precision I supply my collimators with a detachable aperture stop accessory having a knife-edge 1mm pin hole and a white screen front. The stop is included in the basic collimator price. The stop screws into the laser aperture and restricts the beam, producing a tiny circular impact surrounded by a series of concentric rings. The edge of the pinhole diffracts some of the laser light, forming the concentric rings, which facilitate precise centering. With the stop attached to the collimator, the beam impact looks like a star diffraction pattern. The diffracted light that forms the rings is divergent, and this fact allows the stop to also be used to implement a low-contrast form of “Barlowed” collimation, explained below under the heading of Barlowed collimation.
The Holographic Attachments
Optional holographic attachments screw into the laser aperture and have a white screen front surface. They contain an optical element that diffracts most of the laser light into a diverging symmetrical pattern around the central beam. The projected pattern is useful for centering optical elements by making it symmetrical with the edge of the optic.
Three different patterns are available:
- A 10 x 10 line square grid pattern is supplied as standard unless otherwise requested because it is the widest pattern. It spreads 21 degrees which allows centering of optics as fast as f/ 2.7. This pattern is recommended for general use because it can be used with the fastest telescopes likely to be encountered.
- A nine-concentric circle pattern is available that spans 10 degrees and will reach to the edge of f/ 5.7 optics. This pattern is recommended for scopes around this focal ratio or slower. Because the laser light is spread over a smaller area it is brighter than the square grid pattern, and this makes it particularly useful with Cassegrain scopes, where the pattern impact is sometimes scrutinized on the mirror surfaces. The projected pattern is seen only by light that is scattered from dust, dirt, or optical roughness, so a brighter pattern is better, especially if the mirrors are very clean.
- A cross-hair and circle “scope” pattern is available that spans 10 degrees. It has utility for non-Barlowed , conventional Newtonian primary collimation, where the primary is adjusted to return the reflected central laser beam back into the laser aperture of the collimator. The cross-hair intersection makes it easier to see when the return beam is centered on the collimator face.
Howie Glatter Laser pointer 635nm 2" & 1.25"
This dual size 1.25" and 2" collimator is ideal for people who own both focuser sizes. It may be used in a larger focusers with an accurate eyepiece adapter. The adapter itself can be checked for accuracy with the collimator by rotating the adapter and reclamping it, and seeing if the laser spot wanders.
The Laser itself is tuned to a higher brightness than others. Each one comes with a 1mm Aperture Stop for a pin point laser dot. The 635nm laser is more expensive, but it enables Barlowed or holographic collimation in higher levels of ambient light. All of the collimators are powered by a CR123A lithium cell, giving about 40 hours of service. They come with one battery, a plastic case and collimation donuts.
The Holographic and Barlow attachments (Sold Separately) can be used with any Howie Glatter collimator by simply removing the 1mm aperture stop at the end of the collimator and screwing on the attachment of choice.