Collimation
Made Simple -
Howie Glatter’s "The Blug"
by Rob Lambert
Ever since purchasing my 10-inch Intelliscope back in October 2005, I have been disappointed that collimating my scope hasn’t been the exact science that I thought it should have been. Collimating Newtonian reflectors has been the bane of amateur astronomers for years. It has been the first fear realized by the new amateur astronomer and is a source of frustration for many even today. There have been quite a few devices developed over the years to assist the amateur astronomer in this somewhat daunting task. They all work to some varying degree of accuracy, depending on the skill and patience of the one doing the collimating.
My first attempt at collimating my Intelliscope was done with the simple collimating cap provided with my telescope. Although you can get close to aligning the mirrors with the collimating cap, the result is only as good as your ability to estimate getting three circles to be concentric or centered within each other. After collimating my scope for the first time, I asked three different people to check the collimation and each one of them felt it was off and made additional corrections in an attempt to improve it. That should have been an indication as to how precise or imprecise the collimating cap is.
I have purchased two other collimating tools - a Cheshire eyepiece and a Lasermate Deluxe. Each of these devices assists in the collimation process in slightly different ways. One would think that if you collimate your scope with one device and check it with another, the results should be the same. Well, let me just say that using one device and checking with another left me wondering whether I would ever be able to reasonably collimate my scope. It didn’t matter which device I used first, verifying the collimation with the second device always left me wondering which one was correct. I was never able to feel that I had ever achieved a good collimation with either device.
All of this changed at this year’s Death Valley Star Party. Several month’s prior to the Star Party, I had told Doug Phillipson about a new collimating aide that had been developed based on the highly touted barlowed laser concept. This new device was developed by Howie Glatter and is called the Blug. Doug purchased a Blug to evaluate with his Discovery 15- inch Truss Dob. While at Death Valley, I borrowed Doug’s Blug and his Helix Laser and attempted to collimate my scope in the dark. Using the simple instructions provided with the Blug, I achieved the best collimation of my scope ever. Stars became tight pinpoints of light rather than sea-gulls, comets, or other malformed shapes. The Trapezium in the Orion Nebula literally jumped out of the nebula’s cloud. I was so impressed with the ease of use and the results of my collimation with the Blug, that I went to Rick Lamison and Brett Platko, who had similar scopes, and shared the technique with them and equally improved the collimation of their scopes. Both were truly impressed with the improved views through their scopes.
Ok, so what is the Blug and why is collimation easier and seems to be more accurate than with other devices? The Blug is a modification of the Barlowed Laser. It contains a barlow that diffuses the beam of a collimation laser. The main difference between the Blug and other barlowed lasers is that the Blug has a white face slanted at 45 degrees. This makes the Blug easier to use than barlowed lasers where the white face is perpendicular to the laser beam. It also facilitates using the Blug with large Truss Dobs without having to move back and forth between the collimation knobs and the eyepiece.
After using either a collimating cap or cheshire eyepiece to ensure your secondary mirror is centered in the focuser, use a laser without the Blug to adjust the tilt of your secondary mirror and center the laser beam in the donut on the primary mirror. This ensures the secondary mirror is correctly aligned on the primary. Any laser will do, as long as it is of sufficient quality to provide a stable collimated beam that doesn’t wobble as the laser sits in the focuser. Single beam or cross-hair hollographic lasers work well in aligning the tilt of the secondary mirror. (See the sample photos below.) Adjust the tilt of the secondary mirror with the adjusting screws on the secondary mirror holder.
Secondary not aligned - laser is hitting primary outside the donut
Secondary aligned so that laser is centered in donut
Once you are satisfied that the laser is hitting the exact center of the primary, it’s time to insert the Blug into the focuser, from the inside of the tube. Ensure the Blug fits snugly in the focuser and is seated completed inside the focuser tube. Orient the Blug’s white face so that you can see the face as you adjust the primary mirror. Using the Blug with closedtube telescopes will require you to move from the primary adjusting knobs to front of the tube as adjustments are made.
Turn the Blug so that the face can be easily seen. With a closed-tube scope like the Orion Intelliscope, the Blug’s white face will be oriented toward the front opening of the tube. With a truss dob, the face can be turned toward the bottom of the scope so that it can be seen through the trusses while you are at the adjusting knobs. The barlow in Blug will diffuse the laser and cast a shadow of the primary mirror’s donut back onto the face of the Blug. The shadow of the donut should be somewhere on the face of the Blug. (See below) Now it’s a simple matter of adjusting the primary mirror to center the shadow on the hole in the center of the Blug’s face using your scopes primary adjustment knobs.
Donut shadow still below the Blug’s central hole.
The primary’s donut is now properly centered on the Blug’s central hole.
Once the shadow is centered on the hole, the scope should be collimated. If your scope was very badly out of collimation at the beginning, it’s a good idea to remove the Blug at this point, and verify that the laser beam is still centered on the primary mirror. If it is, you have collimated your scope. If not, simply repeat the previous steps, beginning with adjusting the secondary tilt to further refine your collimation. You should not have to repeat the process more than once and the whole collimating process should take no more than five minutes, once you’ve done it a couple of times.
The Blug is available from Howie Glatter’s website, www.greatredspot.com for $65 for the 2-inch version. It comes with plastic shims for providing a tight fit in almost any focuser. Do not throw these away. I required two of them for the Blug to fit my new Orion focuser tightly. Another website you should visit is Howie’s Collimation page at www.collimator.com, where he fully explains collimation.
Note: All photos were taken by the author, using personally owned equipment. The Blug and a laser are now the primary devices used in collimating my Orion Intelliscope. Before laying out $65 for the Blug, you are welcome to try mine to collimate your reflector at the next LVAS Star Party.