2" vs 1.25" collimation tools

I have read a number of posts recently that speak about the application of 2" collimation devices.

I have always thought that one was better off collimating with 1.25" tools because it was only at high power where one would notice the precision of collimation (or lack of it). High power for most telescopes is normally achieved with 1.25" EPs.

My thoughts were always try to achieve the best collimation with the accesories that you will use to view at high power. This avoids any potential alignment differences between the 2" barrel of the focuaser and the 1.25" insert.

I am curious about the thoughts of others on this.

Gary Weber

Gary
Good question and I would be interested in hearing from those more skilled than I. I've been working on honing my collimation skills and tuning my scope for the last few weeks and I can see where the 2" tools would be easier because of one less place for error caused by the adapter. However I have achieved a method with 1.25" tools that gets me perfect collimation with NO ghost in a Techron Autocollimator. Now from what I've been reading is that the most critical collimation is the secondary, main mirror and focuser train and any small alignment issues caused buy the adapter and eyepiece tolerances does not cause any problems at the eyepiece. So as far as I can understand is that good collimation is good collimation regardless of the size tools but might be easier with the 2". I think method using the tools might be the most important factor. I might be all wrong here but that's the way I see it now.
Buck
PS Since I only have one 2" eyepiece and all the rest are 1.25" and I also always insert and tighten the set screw on the adapter the same way I get good repeatability

Hi Gary,

IMO, the 1.25" adapter should fit well enough that if the scope is in perfect collimation with a 2", it should also be with a 1.25". My Starmaster has a Feathertouch focuser and when the 2" is in collimation, so is the 1.25" adapter when the autocollimator is snug (as it would be on an eyepiece). To me, the advantage of 2" tools is simply the larger view of what is going on. For example, when using the Tectron 1.25" autocollimator, I found the three reflections of the ring, very difficult to align. This is because very slight movements made the reflections disappear from the field of vision. With the 2" autocollimator, I find the field of vision larger and therefore a good deal easier to see what is going on. Collimation is better with the 2" only (IMO) because it is easier to take a few seconds to get it perfect. With the 1.25", I would make the field darken and when I could see three rings, I would call that "good enough".

I would say if one has a method of using the 1.25" tools that works for them, continue with it. When I did take the time to get collimation perfect with the Tectron 1.25" tools, I could not improve upon it with the 2" Catseye Tools.

Randy

Hi Gary,
I will agree with Randy's post.
However I do believe that many of the focuser's have a poor fit between the 1.25" adapter and the 2" focuser barrel and it is this error that makes the 2" tools superior over the 1.25" tools. When you add the better image (brighter and easier to see) that Randy mentions, it is two things that are in favor of the 2" tools.
The same thing applies with the 1.25" and 2" lasers. I find the 2" lasers always seem to fit better and give repeatable results. The 1.25" lasers tend to point to a different spot each time they are inserted into the focuser. I am sure there are exceptions to this, but so far this has been my observation. Even with the 2" lasers, some are better than others at this.
I just measured the internal diameters of the Feathertouch 2" and 1.25" bores and they are .002" over sized. This is so that the EP barrels will not bind in the bore and is a tolerable amount of play.