What is the Howie Glatter Cross Hair Holographic Attachment used for?
This attachment projects a cross-hair pattern that is primarily used for the final step in collimating a Newtonian telescope: aligning the laser beam reflected from the primary mirror so it returns perfectly to the center of the laser collimator's face.
How do I know if this Cross Hair attachment will fit my Howie Glatter laser collimator?
This attachment fits the current version of Howie Glatter laser collimators, which use a coarser 3/8-32 thread. You can identify these modern collimators by a visible ring. It will not fit older models that used a finer 5/16-56 thread.
Can I use this Cross Hair attachment and the 1mm aperture stop at the same time?
No. The 1 mm aperture stop is not used at the same time as the holographic feature: unscrew the diffractor first, then install the stop in the laser aperture. Screwing the diffractor back on returns the collimator to holographic mode with its alignment kept.
Why would I choose the Howie Glatter Cross Hair attachment over the Square Grid pattern?
You would choose the Cross Hair pattern for its simplicity in a specific task: centering the return beam. The Square Grid pattern is more sensitive for judging the centering of the mirror itself within the pattern, making it better for general-purpose optical alignment. The Cross Hair is a more specialized tool for the final step.
When collimating my Newtonian, at what step is the Howie Glatter Cross Hair attachment most useful?
The Cross Hair attachment is most useful during primary mirror collimation. After your secondary mirror is correctly positioned, you adjust the primary mirror's tilt until the returning laser beam is centered on the face of the collimator. The cross-hair pattern provides a clear target for this final, critical adjustment.
If I use this Howie Glatter attachment on a friend's collimator, will it be as accurate?
Probably not. Original holographic attachments are individually fitted to their specific collimator to achieve an accuracy of 15 arc-seconds. Swapping attachments between different collimators can lose this high precision, though the alignment will still be accurate to within several arc-minutes.
