Laser Collimators

Hi,

I have an Antares Side View Laser Collimator, which is easy to use and seems to work well. But I have read about "Barlowed Laser Collimators". Do I just use what I have with a barlow, or is this something different altogether? If so, what makes it better?

Thanks!

Darryl

Darryl,
Let me preface this by saying that I have no first hand experience yet. But this is my understanding. Yes, you can use your barlow. However, you will need to make a white mask that covers the end of the barlow closest to the secondary. You will have to cleanly cut round hole in the center of that mask (size?) to allow the laser to shine through. What will happen is the the barlow will spread the laser beam out to form a large disk on your primary. This will be reflected back to your secondary and onto the mask that you put on the barlow. In the middle of that reflected image will be a dark shadow that is produced the center spot on your primary, since it should not reflect the light. This shadow is then aligned with the hole in your barlow mask to achieve primary collimation.

Why is this better than what you have? Apparently the laser housing will wiggle somewhat in the focuser, such that your point of light can hit the primary at a slightly different spot each time you place it in the focuser. When reflected back at your laser and appearing on the 45 degree surface you see from the side, the % error at the primary will be even greater by the time gets back to the laser. This can cause alignment errors. Everything I've read says that the spread out beam produced by a barlowed laser returns the dark shadow of the primary center spot in a consistant manner that will not change even if you wiggle the laser in the focuser. That's why I'm going to a barlowed laser setup by Howie Glatter called the Blug. Check collimator.com for more information on that device, if you're interested.

Darryl Simmons said:

Hi,

I have an Antares Side View Laser Collimator, which is easy to use and seems to work well. But I have read about "Barlowed Laser Collimators". Do I just use what I have with a barlow, or is this something different altogether? If so, what makes it better?

Thanks!

Darryl

Darryl:

A few comments on using a Laser for collimation...

- Make sure you laser is collimated itself. Quite often the collimators made in Asian are not even collimated when they arrive at your doorstep. The easiest way to check the collimation is to place the collimator in your focuser and slowly spin it watching the dot on the mirror. It should not move at all, if it moves it means the collimator needs collimation.

- The "Barlowed Laser Technique" was invented by Nils Olof Carlin about 5 or 6 years ago for the purpose of setting the tilt of the primary mirror. The collimator itself is fine for setting the tilt of the secondary but is really inadequate for setting the primary tilt because small errors build up and the primary, in a fast scope, must be right on.

- You can use a standard barlow if it fits reasonably well in the focuser. Placing a paper target with a hole in the center of the barlow helps, I use a target with rings. The barlow disperses the beam and so what you see is the spread out reflection of the beam on the face of the laser. The center ring on the mirror reflects no light so you see a shadow around the laser and merely adjust the primary until the shadow is centered around the laser beam.

I have been using it since it first came out with good success in Newtonians as fast as F/4. I have been using a 1.25 inch Howie Glatter Laser Collimator for about 8 years and recently joined the modern era with a 2 inch Howie Glatter with all the gizmos. The 2 inch fits the focuser better but I had good success with the 1.25 inch. After 8 years I finally dropped it about 5 feet onto the concrete floor in the garage so it is slightly out of collimation but other than needing to go back home to be collimated, it has been flawless.

My only advice is that if you are going to buy one, get a good one, spend the money to buy one that is well made, arrives accurately aligned and stays aligned, one that fits nicely in the focusr without slop... That little extra money is definitely worth it.

jon

I have an Obsession 12.5" reflector on order. I included their barlow-laser collimator in the order, without really knowing anything about it, except what I read in the book "astronomy Hacks."

Has anyone here had experience with that particular device? It is made by AstroSystems.

Thanks in advance...