↑ For Outer Diameter from 65mm-100mm ↑

↑ For Outer Diameter from 85mm-120mm ↑

↑ For Outer Diameter from 105mm-150mm ↑

↑ For Outer Diameter from 125mm-180mm ↑

↑ For Outer Diameter from 150mm-200mm ↑

↑ For Outer Diameter from 175mm-220mm ↑

↑ For Outer Diameter from 195mm-240mm ↑

↑ For Outer Diameter from 215mm-260mm ↑

↑ For Outer Diameter from 250mm-290mm ↑

↑ For Outer Diameter from 290mm-340mm ↑

About this item

• Bahtinov masks take the guesswork out of focusing and even get over the seeing conditions as it is a mathematical type approach to the task.The best focus for your quickly and easily.
• Suitable for use on all types of reflectors, rafractors, Dobsonians, Mak-Cas and SCTs. They are made from precision laser cut enforced plexiglass, which is stiff and long lasting. They will never be brittle in the cold, unlike some other masks which are made from normal plastics.
• The masks grip the tube gently but firmly with three metal posts which have non-scratching silicon sleeves to protect you valued surface. This prevents slippage, whilst allowing the to remaining perfectly central. Because of this 3-post mounting, the remains centered, whilst fitting a wider range of telescopes.
• They are made from 2mm thick laser cut plexiglass and the securing screws are capped with soft plastic so that they do not damage your These high quality Bahtinov masks are adjustable to fit a wide range of optical tubes, unlike masks which are only able to fit one They have adjustment latitude of about 250-290mm, depending on model, in aperture making them very versatile.
• Please be assured that these focusing masks will work excellently for both reflectors and refractors with whatever focal length. All you need to do is to measure your tube size and choose the right size of the contact us if you are not sure where to measure).

Product Description

Astromania Bahtinov Focusing for Telescopes

The Bahtinov has become the preferred method of focusing a 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 over the front of your ‘scope, align the scope towards a star. The 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.

Specifition

• Nominal size: 250-290mm
• Material: made of sturdy plastic.
• Thickness: 2mm
• min outer diameter: 245mm
• max inner diameter: 300mm

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 toinside of the s front cell or dew shield, then tighten the thumbscrews. Suitable for use with telescopes with inter diameters ranging from257mm to 300mm, the max inter diameter is300mm.

• 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 clampoutside of the s front cell or dew shield, then tighten the thumbscrews. Suitable for use with telescopes with outer diameters ranging from245mm to 288mm, the min outer diameter is245mm.

FOCUS ON A STAR FIRST, THEN MOVE THE TO THE PLANET FOR IMAGING

• A “live view” imageis best if yourcameraorsoftwarepermits it, because then you’ll be able to see the results of your focus adjustments in real time, and the focusing process will befaster. If needed, though, you can takesuccessive still exposures and review each exposure on the screen,tweaking the 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 aclear view of the spike pattern, in particular, thecenter spike’s positionrelative to the othertwo spikes that form the “X”. DSLRs often havetwo or more magnification settingsfor live view focusing, and capture programs used with a laptop often allow subframe viewing, whichmagnifies the image.
• As you turn your s focus knobs tomove in and out of focus, you should see that center spike move toone side and the other of the X. Make fine adjustments of the focusuntil the center spike lands exactly in the center of the X, that is, it bisects the X. Then you’re in focus!

USING THE FOCUSING TO FOCUS

• With the in placeover the frontof your and your camera attached to the scope and turned on,center a bright star in the field of view. You should see thediffraction spike patternon the camera’s LCD screen (for DSLRs) or on your laptop computer running your preferred image capture software (see above figure) . If the scope isgrossly out of focusyou may see the grid pattern of the in which case you shouldadjust the scope’s focustoshrink downthe grid patternuntil it turns into a dot with spikes.
• Once focus isachieved, remove the focusing Then you’re all set tophotograph any object at infinity focus.

Make sure the 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 gently toward the loosened grip peg. This will make sure that the other two grip pegs are contacting the when you retighten the third thumbscrew. Now the should be well secured in position over the front of the You’re ready to focus!