I have been reading as much material I can find in CN and the web on the use of the holographic attachment and I noticed a common misconception about what to look for and how to interpret what is seen.
Seeing the whole grid as shown below does not mean much especially when the attachment is located below the focal plane.
Some believe that as long as the grid is symmetrical with respect to the primary mirror perimeter then the secondary mirror is well positioned under the focuser. That is incorrect. When the central beam of the grid is aligned with the primary mirror center spot, then the grid will always be seen symmetrical. There is no need to check for symmetry – just aligned the central beam with the primary center spot. You will never run into the scenario shown below:
What you need to look for is the truncation or clipping of the grid by the secondary mirror edge. As you rack the laser collimator out, the grid will get larger and will eventually get clipped. Depending on how oversized the secondary mirror and the F-ratio of the scope, The grid clipping might not be seen concentric with the primary mirror for a well-positioned secondary – shifted slightly towards the focuser as shown below:
If you rack the attachment above the focal plane, then you you will get to a point where the clipped grid covers only the primary mirror. This can only occur for a well-positioned secondary mirror as shown below:
I had to use a 2” drawtube extension to take the following photo.
If the holographic attachment is located at or below the focal plane and the grid is clipped but does not cover the whole primary mirror then the secondary mirror is too small.
On the other hand, if the the whole (unclipped) grid is visible but smaller than the primary mirror then it does not mean much. Always remeber that a "clipped" grid will tell us something about the position of the secondary mirror with respect to the focuser because the "clipping" is a direct result of the interaction of the secondary mirror edge with the grid.
In the following photo, the whole grid is visible within the primary mirror which does not tell me much about the secondary mirror placement.
By the way, you could use the first circle of the concentric circles holographic attachment against the outer edge of the HotSpot to align the focuser axis.