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Astromania Bahtinov Mask Focusing Mask for Telescopes - FM60mm for a tube outer diameter (OD) from 65mm-100mm

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Astromania Bahtinov Mask Focusing Mask for Telescopes
The Bahtinov mask has become the preferred method of focusing a telescope, either visually or when imaging with a CCD camera, DSLR or webcam. They are an inexpensive tool which will allow you to achieve pin-sharp levels of focus, saving you time and improving your work. Simply place the mask over the front of your ‘scope, align the scope towards a star. The mask displays a unique diffraction profile, one part of the diffraction pattern moves in response to changes in focus and displays error as a displacement from a clearly defined point.



•  Nominal size: 65-100mm
•  Material: made of sturdy plastic.
•  Thickness: 2mm
•  Telescope min outer diameter:60mm
•  Telescope max inner diameter:110mm

Two Installation Modes

•  Inside The Dew Tube
Place the brass screw on the inside of the the dew tube. Slide each of the three grip pegs inward until they cling to inside of the telescope’s front cell or dew shield, then tighten the thumbscrews. Suitable for use with telescopes with inter diameters ranging from 72mm to 110mm, the max inter diameter is 110mm.

•  Outside The Dew Tube
Place the brass screw on the outside of the the dew tube. Slide each of the three grip pegs inward until they clamp outside of the telescope’s front cell or dew shield, then tighten the thumbscrews. Suitable for use with telescopes with outer diameters ranging from 60mm to 98mm, the min outer diameter is 60mm.


  A “live view” image is best if your camera or software permits it, because then you’ll be able to see the results of your focus adjustments in real time, and the focusing process will be faster. If needed, though, you can take successive still exposures and review each exposure on the screen, tweaking the telescope’s focus slightly after each exposure, then taking another one. In either case, you’ll want to “zoom in” as needed so you can get a clear view of the spike pattern, in particular, the center spike’s position relative to the other two spikes that form the “X”. DSLRs often have two or more magnification settings for live view focusing, and capture programs used with a laptop often allow subframe viewing, which magnifies the image.
•  As you turn your telescope’s focus knobs to move in and out of focus, you should see that center spike move to one side and the other of the X. Make fine adjustments of the focus until the center spike lands exactly in the center of the X, that is, it bisects the X. Then you’re in focus!


•  With the mask in place over the front of your telescope and your camera attached to the scope and turned on, center a bright star in the field of view. You should see the diffraction spike pattern on the camera’s LCD screen (for DSLRs) or on your laptop computer running your preferred image capture software (see above figure) . If the scope is grossly out of focus you may see the grid pattern of the mask, in which case you should adjust the scope’s focus to shrink down the grid pattern until it turns into a dot with spikes.
•  Once focus is achieved, remove the focusing mask. Then you’re all set to photograph any object at infinity focus.

Make sure the mask is centered on the front of the scope

Adjust the pegs so that each is at roughly the same position in its slot. To ensure a tight grip, loosen one thumbscrew slightly, then push the grip peg inward while pulling the mask gently toward the loosened grip peg. This will make sure that the other two grip pegs are contacting the telescope when you retighten the third thumbscrew. Now the mask should be well secured in position over the front of the telescope. You’re ready to focus!


  • 【Practical Function】It's easy to focus your DSLR, CMOS or CCD camera for astrophotography by adding a focusing mask that matches the diameter of your telescope.
  • 【3-Post Mounting】The mask uses three metal posts which have non-scratching silicon sleeves to gently and firmly clamp the telescope sleeve. This prevents slippage, whilst allowing the mask to remaining perfectly central.
  • Lightweight Design】They are made from 2mm thick laser cut plexiglass, light weight wont upset the balance on your scope.
  • 【Specification】They have adjustment latitude of about 65-100mm, depending on model. Suitable for reflectors, rafractors, Dobsonians, Mak-Cas and SCTs. All you need to do is to measure your telescope tube size and choose the right size of the mask (contact us if you are not sure where to measure).
  • 【Easy to Use】Use by simply placing the Bahtinov focus mask over the front of your telescope, record a quick image of a bright star, adjust focus and until perfect focus is achieved.
  • We only ship to confirmed order addresses. Your order address MUST MATCH your Shipping address.
  • Your order will be shipped within 2 business day normally once we receive your payment.
  • We will provide an online tracking number to you once the item has been shipped.
  • If you have any problem with shipment, please feel free to contact us. We will track the shipment and get back to you as soon as possible with a reply. Our goal is customer satisfaction!
  • If you have special needs or you live in area where only specific carrier is available please inform us prior to shipping.
Average rating: 5.0 based on 72 reviews
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