What is a collimation eyepiece

Check adjustment

Adjustment aids


Omegon Newton alignment laser 1.25 '' with viewing window - astroshop.de A reflective telescope reflects the light rays to the focal point in order to pick them up with the eyepiece. For this purpose, the optical axes must be aligned with one another as precisely as possible in order to avoid blurred, distorted and low-contrast images. The full telescope performance is achieved by regularly checking the adjustment status.

Various instruments are available for this, the selection of which is at the discretion of the observer according to the demand for perfection and ease of use.

A simple but inexpensive option is to build an adjustment aid from a film canister yourself to check the alignment of the secondary and main mirrors.

Alignment laser


Howie Glatter tublug 1.25 '' - astroshop.de When using a laser, a bundled light beam is first directed from the focuser via the secondary mirror onto the main mirror. From there it is reflected again and, if the two components are precisely aligned, it returns to its origin on a marking surface.

The laser itself must, however, also be adjusted and sit firmly in the focuser. With its own light source, the system offers an advantage for checking in the dark and is easy to operate. However, not all adjustment parameters can be checked with simple systems.

Cheshire eyepiece

Omegon collimation eyepiece - astroshop.de A Cheshire eyepiece works similarly to an alignment laser with regard to the alignment principle of the secondary and primary mirror. However, there is a reflective surface that directs outside light into the telescope in order to allow it to exit the eyepiece again after being reflected in the telescope.

This is checked with the eye and the components are brought into conformity if necessary. A crosshair at the end of the sight tube supports the alignment and also allows the focuser to be checked.

It can be used in the dark if the eyepiece is illuminated from the side with a red light. For easy adjustment, the adjustment screws of the main mirror should be accessible by hand when looking into the eyepiece so that the result can be corrected directly if necessary.