Farpoint Carey Masks Are one of the best tools for manually focusing your telescope available to astrophotographers.

In 2009, George Carey, an amateur telescope maker and astronomer from the UK, published a modification of previous focus mask designs to make a much more sensitive version of the device..

Carey mask are a less expensive method of getting focus on objects in the night sky compared to a standard motor focuser.
With the right mask and setup it's easy to get crystal clear focus on a star in less than 90 seconds.
How it Works
These mask will work equally as well on the end of a scope or on the end of a dew shield on top of that the mask itself does not need to be perfected centered on the scope this is due to the angle of the slits themselves. Select a bright star as your guiding object. Place the Carey focusing mask on your telescope's lens and secure it into place using the rubber tabs. The slits in the mask design create a set of diffraction spikes on the star that will assist in the accuracy of your focus. It will appear on your screen or computer as an "X" with a line through the center (when in focus).
The diffraction spike pattern from a bright star using a Carey mask As you adjust the focuser of your telescope, the central spike will move in and out of the X-pattern. If you are using capture software be sure to compensate for the lag time between exposures on the screen, typically 4-5 seconds. The same process applies using Live view display on your DSLR camera.
Who We areWe at Farpoint Astro are a California based manufacturer of astrophotography filters, scopes, and tools. Our Carey masks are the highest quality in the Astronomy Space