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Farpoint Bahtinov Mask for Refractors or Newtonians with 3.5" to 6.5" Front Diameter - FP401


Farpoint Bahtinov Mask
for 3.5" - 6.5" OD Telescopes and Dew Shields

The Bahtinov Mask makes it easy to focus your DSLR camera, CCD camera, or webcam when imaging the night sky. The Farpoint Astro Medium Bahtinov Mask works with any telescope with an outside diameter of between 3.5" and 6.5". Measure your diameter from the end of the tube or dew shield.

How to Use the FarPoint Bahtinov Mask

Attach a camera to your telescope, center a fairly bright star and achieve rough focus. Then place the mask over the front aperture of your telescope by “hanging” it on the plastic screws from the front of your telescope or dew shield. It is recommended that you pick an orientation for the mask and then use that same orientation each time. This way you will get used to the way a star looks when it is inside or outside of focus. Take a short exposure. The image of the star will show diffraction spikes. The “center” set will most likely be shifted to one side or the other. What you are shooting for is a symmetrical diffraction pattern, where the center spike is actually centered over the star and the spikes to either side are symmetrically spaced as well.

Adjust the focus of the telescope and re-expose the star to show you the diffraction spike pattern once again. Repeat the process until the central diffraction spike is centered against the star and the other spikes. When a symmetrical pattern is achieved, the best possible focus is then reached. Simply remove the mask, center the target object and take amazing, sharp images!

PS: The blue strap in the main photo is not included. The manufacturer just used it to hold the mask upright for the photo.