3D Astro Bahtinov Focus Mask
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Important: Please note that this is a 3-D printed plastic mask. More info below.
A. About Bahtinov Focusing Masks
Bahtinov masks can be a great aid in focusing your guidescope or telescope for astroimaging. With the mask on, you can see a diffraction spike pattern. Focus until you achieve a symetrical spike pattern. Once the best focus has been achieved, you can remove the mask and use the guide scope or telescope normally.
B. Selecting the correct Bahtinov Mask for your telescope
- This mask is designed to be placed on the front (sky-end) of your telescope, spotting scope, guidescope or camera lens for focusing, and should then be removed without disturbing the imaging setup.
- Hence, do not get a mask that fits snugly or tightly like an end cap. A mask that just sits loosely on the dewshield and which may fall off due to gravity if the scope is pointed downwards is just fine.
- For this reason, we recommend that you purchase a mask that is 1-3 mm larger that the outside telescope tube or dewshield diameter.
- To get the proper fit, measure the outside diameter very carefully by using a caliper, ruler, or tape measure. See the 4th product photo above. Measure the widest distance of the telescope tube starting from the exterior of the casing, across the center and to the exterior part of the casing on the other side.
- Measure using a millimeter (mm) ruler if possible. If you measure in inches, convert to mm by multiplying by 25.4.
- For example, if your dewshield is 4-1/4" = 4.25 x 25.4 = 107.95mm in diameter, select a Bahtinov Mask with an inside diameter of 110mm (# BM-110) from the drop-down list above.
- Again, measure carefully before ordering and select a marginally larger size to avoid disappointment and expensive returns.
C. Additional notes
- Bahtinov masks may not be effective for very small aperture guidescopes (under 50mm) or lenses with short focal lengths. This is a gray area - some people find these useful on small scopes and others, don't so your mileage may vary and we cannot make any recommendations for small scopes.
- 3D printed from PLA.
- Color of current stock is silver-gray but is subject to change without notice.
| Mask Size | Products Applicable |
| BM-42 | William Optics 32mm Guidescope |
| BM-44 | ZWO 30mm f/4 Guidescope |
| BM-52 |
Askar 40mm Guidescope # FMA180 |
| BM-58 |
Askar 40mm Guidescope - PRO# FMA180-PRO |
| BM-60 | William Optics 50mm Guidescope |
| BM-62 |
Agena 50mm DLXGS |
| BM-68 | ZWO 60mm Guidescope |
| BM-70 | Askar 50mm Guidescope # FMA230 |
| BM-82 | Takahashi FS-60 |
| BM-84 | Sharpstar 61EDPH III Only |
| BM-90 | Sharpstar 65PHQ |
| BM-92 |
Sharpstar 61mm EDPH II Only / Radian Raptor Askar SQA55 Refractor |
| BM-100 | Askar 200mm Lens # ACL200 |
| BM-102 | Askar 72mm Quintuplet # FRA400 |
| BM-116 | Askar 90mm Quintuplet # FRA500 |
| BM-122 | Askar 103APO |
| BM-126 | Sharpstar Z4 100mm Astrograph # Z4 |
| BM-136 | Askar 107mm Quadruplet # 107PHQ |
| BM-148 | SkyWatcher Espirit 100mm ED |
| BM-150 | Askar 108mm Quintuplet # FRA600 |
We are in the process of building the table above. If your scope is not listed above, we do not know which mask might work for you. If you have a suggested entry for the table above to help other customers, please do send us an email with this info (scope dewshield/tube diameter and mask size you used).
Other Information
- Country of Manufacture: United States
Important: Please note that this is a 3-D printed plastic mask. More info below.
A. About Bahtinov Focusing Masks
Bahtinov masks can be a great aid in focusing your guidescope or telescope for astroimaging. With the mask on, you can see a diffraction spike pattern. Focus until you achieve a symetrical spike pattern. Once the best focus has been achieved, you can remove the mask and use the guide scope or telescope normally.
B. Selecting the correct Bahtinov Mask for your telescope
- This mask is designed to be placed on the front (sky-end) of your telescope, spotting scope, guidescope or camera lens for focusing, and should then be removed without disturbing the imaging setup.
- Hence, do not get a mask that fits snugly or tightly like an end cap. A mask that just sits loosely on the dewshield and which may fall off due to gravity if the scope is pointed downwards is just fine.
- For this reason, we recommend that you purchase a mask that is 1-3 mm larger that the outside telescope tube or dewshield diameter.
- To get the proper fit, measure the outside diameter very carefully by using a caliper, ruler, or tape measure. See the 4th product photo above. Measure the widest distance of the telescope tube starting from the exterior of the casing, across the center and to the exterior part of the casing on the other side.
- Measure using a millimeter (mm) ruler if possible. If you measure in inches, convert to mm by multiplying by 25.4.
- For example, if your dewshield is 4-1/4" = 4.25 x 25.4 = 107.95mm in diameter, select a Bahtinov Mask with an inside diameter of 110mm (# BM-110) from the drop-down list above.
- Again, measure carefully before ordering and select a marginally larger size to avoid disappointment and expensive returns.
C. Additional notes
- Bahtinov masks may not be effective for very small aperture guidescopes (under 50mm) or lenses with short focal lengths. This is a gray area - some people find these useful on small scopes and others, don't so your mileage may vary and we cannot make any recommendations for small scopes.
- 3D printed from PLA.
- Color of current stock is silver-gray but is subject to change without notice.
| Mask Size | Products Applicable |
| BM-42 | William Optics 32mm Guidescope |
| BM-44 | ZWO 30mm f/4 Guidescope |
| BM-52 |
Askar 40mm Guidescope # FMA180 |
| BM-58 |
Askar 40mm Guidescope - PRO# FMA180-PRO |
| BM-60 | William Optics 50mm Guidescope |
| BM-62 |
Agena 50mm DLXGS |
| BM-68 | ZWO 60mm Guidescope |
| BM-70 | Askar 50mm Guidescope # FMA230 |
| BM-82 | Takahashi FS-60 |
| BM-84 | Sharpstar 61EDPH III Only |
| BM-90 | Sharpstar 65PHQ |
| BM-92 |
Sharpstar 61mm EDPH II Only / Radian Raptor Askar SQA55 Refractor |
| BM-100 | Askar 200mm Lens # ACL200 |
| BM-102 | Askar 72mm Quintuplet # FRA400 |
| BM-116 | Askar 90mm Quintuplet # FRA500 |
| BM-122 | Askar 103APO |
| BM-126 | Sharpstar Z4 100mm Astrograph # Z4 |
| BM-136 | Askar 107mm Quadruplet # 107PHQ |
| BM-148 | SkyWatcher Espirit 100mm ED |
| BM-150 | Askar 108mm Quintuplet # FRA600 |
We are in the process of building the table above. If your scope is not listed above, we do not know which mask might work for you. If you have a suggested entry for the table above to help other customers, please do send us an email with this info (scope dewshield/tube diameter and mask size you used).
Important: Please note that this is a 3-D printed plastic mask. More info below.
A. About Bahtinov Focusing Masks
Bahtinov masks can be a great aid in focusing your guidescope or telescope for astroimaging. With the mask on, you can see a diffraction spike pattern. Focus until you achieve a symetrical spike pattern. Once the best focus has been achieved, you can remove the mask and use the guide scope or telescope normally.
B. Selecting the correct Bahtinov Mask for your telescope
- This mask is designed to be placed on the front (sky-end) of your telescope, spotting scope, guidescope or camera lens for focusing, and should then be removed without disturbing the imaging setup.
- Hence, do not get a mask that fits snugly or tightly like an end cap. A mask that just sits loosely on the dewshield and which may fall off due to gravity if the scope is pointed downwards is just fine.
- For this reason, we recommend that you purchase a mask that is 1-3 mm larger that the outside telescope tube or dewshield diameter.
- To get the proper fit, measure the outside diameter very carefully by using a caliper, ruler, or tape measure. See the 4th product photo above. Measure the widest distance of the telescope tube starting from the exterior of the casing, across the center and to the exterior part of the casing on the other side.
- Measure using a millimeter (mm) ruler if possible. If you measure in inches, convert to mm by multiplying by 25.4.
- For example, if your dewshield is 4-1/4" = 4.25 x 25.4 = 107.95mm in diameter, select a Bahtinov Mask with an inside diameter of 110mm (# BM-110) from the drop-down list above.
- Again, measure carefully before ordering and select a marginally larger size to avoid disappointment and expensive returns.
C. Additional notes
- Bahtinov masks may not be effective for very small aperture guidescopes (under 50mm) or lenses with short focal lengths. This is a gray area - some people find these useful on small scopes and others, don't so your mileage may vary and we cannot make any recommendations for small scopes.
- 3D printed from PLA.
- Color of current stock is silver-gray but is subject to change without notice.
| Mask Size | Products Applicable |
| BM-42 | William Optics 32mm Guidescope |
| BM-44 | ZWO 30mm f/4 Guidescope |
| BM-52 |
Askar 40mm Guidescope # FMA180 |
| BM-58 |
Askar 40mm Guidescope - PRO# FMA180-PRO |
| BM-60 | William Optics 50mm Guidescope |
| BM-62 |
Agena 50mm DLXGS |
| BM-68 | ZWO 60mm Guidescope |
| BM-70 | Askar 50mm Guidescope # FMA230 |
| BM-82 | Takahashi FS-60 |
| BM-84 | Sharpstar 61EDPH III Only |
| BM-90 | Sharpstar 65PHQ |
| BM-92 |
Sharpstar 61mm EDPH II Only / Radian Raptor Askar SQA55 Refractor |
| BM-100 | Askar 200mm Lens # ACL200 |
| BM-102 | Askar 72mm Quintuplet # FRA400 |
| BM-116 | Askar 90mm Quintuplet # FRA500 |
| BM-122 | Askar 103APO |
| BM-126 | Sharpstar Z4 100mm Astrograph # Z4 |
| BM-136 | Askar 107mm Quadruplet # 107PHQ |
| BM-148 | SkyWatcher Espirit 100mm ED |
| BM-150 | Askar 108mm Quintuplet # FRA600 |
We are in the process of building the table above. If your scope is not listed above, we do not know which mask might work for you. If you have a suggested entry for the table above to help other customers, please do send us an email with this info (scope dewshield/tube diameter and mask size you used).
Other Information
- Country of Manufacture: United States
3D Astro Bahtinov Focus Mask