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Farpoint Bahtinov Mask for 8.5" to 10.5" Diameter Telescopes - FP404

SKU: FAR-FP404

Farpoint Bahtinov Focus Mask for 8.5" - 10.5" Telescopes


Made of essentially indestructible ABS plastic, Farpoint Bahtinov Masks provide easier, more intuitive DSLR camera, CCD camera, or webcam focusing for a smoother night sky imaging experience. This larger Bahtinov Mask is compatible with dew shields or telescopes that have outside diameters ranging from 8.5" to 10.5". To properly assess your outside diameter, measure from the front end of the optical 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!

Please Note: This Bahtinov Mask will work with all telescopes that fall within the stated size range, but if you have a Schmidt-Cassegrain, please be aware that you have an alternative. FarPoint makes Bahtinov Masks for SCT telescopes with a hole in the center, and this hole fits nicely over your secondary mirror holder to keep the Bahtinov mask in place without the need for other attachment methods. If you'd like an SCT Bahtinov Mask, buy the model made for the aperture of your Celestron or Meade SCT. However, if you'd rather use the mask design that attaches to the outer diameter of the scope or dew shield, it works just fine.

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