Agena 1.25" Cheshire Collimating Eyepiece for Newtonian Reflectors
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This is a great accessory for precisely collimating the optics of your Newtonian reflector telescope to achieve the best image the telescope can deliver.
The aluminum tube is a combination sight tube and Cheshire eyepiece. Peephole in the top and thin wire crosshairs at the bottom allow quick and precise centering of the optics. Fits in 1.25" focusers or in 2"-1.25" adapters. All metal construction.
Item weighs 6.4oz. Total length is approx. 148mm / 5.8". Insertion length is 35mm / 1.38".
The clear aperture of this Cheshire is 21.6mm / 1.13”. Please see schematic diagram in photo 2 above for detailed measurements.
Please note that no instructions are included with the item but these and other tutorials can be found easily on the internet. As with most other telescope collimation/alignment procedures, use of this accessory requires some patience and experience.
Given the dimensions of this Cheshire, it’s possible to sight the full aperture of the primary and secondary of a Newtonian with a focal ratio of approximately f/5 and slower. With faster scopes, it may be necessary to pull the Cheshire out of the focuser somewhat to see the outer edge of the secondary and adjust it so it’s in the center of the field. This adjustment is usually required if the secondary is removed from the tube and replaced, or if it was badly positioned at the factory. When the Cheshire is pulled out slightly, it may be difficult to see the edge of the primary, but if the primary has an accurately placed center dot, alignment remains straightforward. For example, we’ve used this Cheshire to quickly collimate Newtonians with a focal ratio of f/4.7. For scopes with focal ratios of f/4.5 or faster, a shorter Cheshire or sighting tube (or a laser collimator) may be required because of the large secondary.
Other Information
- Country of Manufacture: China
This is a great accessory for precisely collimating the optics of your Newtonian reflector telescope to achieve the best image the telescope can deliver.
The aluminum tube is a combination sight tube and Cheshire eyepiece. Peephole in the top and thin wire crosshairs at the bottom allow quick and precise centering of the optics. Fits in 1.25" focusers or in 2"-1.25" adapters. All metal construction.
Item weighs 6.4oz. Total length is approx. 148mm / 5.8". Insertion length is 35mm / 1.38".
The clear aperture of this Cheshire is 21.6mm / 1.13”. Please see schematic diagram in photo 2 above for detailed measurements.
Please note that no instructions are included with the item but these and other tutorials can be found easily on the internet. As with most other telescope collimation/alignment procedures, use of this accessory requires some patience and experience.
Given the dimensions of this Cheshire, it’s possible to sight the full aperture of the primary and secondary of a Newtonian with a focal ratio of approximately f/5 and slower. With faster scopes, it may be necessary to pull the Cheshire out of the focuser somewhat to see the outer edge of the secondary and adjust it so it’s in the center of the field. This adjustment is usually required if the secondary is removed from the tube and replaced, or if it was badly positioned at the factory. When the Cheshire is pulled out slightly, it may be difficult to see the edge of the primary, but if the primary has an accurately placed center dot, alignment remains straightforward. For example, we’ve used this Cheshire to quickly collimate Newtonians with a focal ratio of f/4.7. For scopes with focal ratios of f/4.5 or faster, a shorter Cheshire or sighting tube (or a laser collimator) may be required because of the large secondary.
This is a great accessory for precisely collimating the optics of your Newtonian reflector telescope to achieve the best image the telescope can deliver.
The aluminum tube is a combination sight tube and Cheshire eyepiece. Peephole in the top and thin wire crosshairs at the bottom allow quick and precise centering of the optics. Fits in 1.25" focusers or in 2"-1.25" adapters. All metal construction.
Item weighs 6.4oz. Total length is approx. 148mm / 5.8". Insertion length is 35mm / 1.38".
The clear aperture of this Cheshire is 21.6mm / 1.13”. Please see schematic diagram in photo 2 above for detailed measurements.
Please note that no instructions are included with the item but these and other tutorials can be found easily on the internet. As with most other telescope collimation/alignment procedures, use of this accessory requires some patience and experience.
Given the dimensions of this Cheshire, it’s possible to sight the full aperture of the primary and secondary of a Newtonian with a focal ratio of approximately f/5 and slower. With faster scopes, it may be necessary to pull the Cheshire out of the focuser somewhat to see the outer edge of the secondary and adjust it so it’s in the center of the field. This adjustment is usually required if the secondary is removed from the tube and replaced, or if it was badly positioned at the factory. When the Cheshire is pulled out slightly, it may be difficult to see the edge of the primary, but if the primary has an accurately placed center dot, alignment remains straightforward. For example, we’ve used this Cheshire to quickly collimate Newtonians with a focal ratio of f/4.7. For scopes with focal ratios of f/4.5 or faster, a shorter Cheshire or sighting tube (or a laser collimator) may be required because of the large secondary.
Other Information
- Country of Manufacture: China
Agena 1.25" Cheshire Collimating Eyepiece for Newtonian Reflectors