Aluminum Bahtinov Telescope Astronomy Focusing Mask Caliber Fixed Diameter Lens

Description

Aluminum Bahtinov Telescope Astronomy Focusing Mask Caliber Fixed Diameter Lens
Note :
1,When you buy it , you need to check your out-diameter of the tube .Not just the Objective lens diameter  .Becasie you need to put the item one the tube.
2,if you don't know which size should to choose you can ask me before buy it , Thanks
3,The size is not the diameter of the item, pls check the measurement way .
For example :
Your telescope is 80mm , but you need to know that the telescpe tube diameter must be bigger then the 80mm , so at least you need to choose the 85-120mm .
Place the Bahtinov Focus-Mask over the end of your telescope, then locate a bright star near your target, take a 3-5 second picture and view the diffraction spikes. Change your focus, take another picture and again, view your diffraction spikes. Is the center spike moving further from center? Then change the direction your focusing and try another picture. Watch the direction the spikes are moving and when the center spike passes the middle of the other two spikes, change direction and fine tune your tuning knobs until the center spike is in the middle. Your now in perfect focus.
Features:
The Bahtinov Mask Made of aluminum alloy, not plastic. And it has whole anodizing aluminium process
Masks now feature 3 holes which can be attached with 3 screws to prevent the mask from falling all the way to the ground
Perfect focusing for your CCD, DSLR or Webcam in seconds
Light weight so you wont upset the balance on your scope
Suitable for telescopes front end diameter 85mm to 120mm/105mm to 150mm/150mm to 200mm/ 65mm to 100mm/175-220mm ,Universal adaptation, 3 bolts with plastic cover allow the mask to be simply attached to any telescope
Aluminium alloy material thickness: 1 mm
Weight: 32g/50g/79g
Color: Black