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M92 to M63 Adapter for William Optics FLT91
This M92 to M63 adapter provides the essential 10.5 mm of optical path length required to connect a William Optics Flat6AIII flattener to an FLT91 refractor. It is a purpose-built component designed to achieve precise back focus for a flat, corrected field of view.
A Purpose-Built Connection for the FLT91 and Flat6AIII at 10.5mm
This is not a generic thread converter; it is an essential optical component for imagers using the William Optics FLT91 telescope with the Flat6AIII flattener/reducer. The adapter's 10.5 mm length is precisely calculated to establish the correct spacing between the telescope's optics and the flattener, which is critical for achieving sharp stars across the entire imaging sensor.
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Telescope-Side Connection: The male M92 thread attaches directly to the focuser drawtube of the FLT91 telescope.
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Flattener-Side Connection: The female M63 thread accepts the nosepiece of the Flat6AIII flattener/reducer.
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Critical Spacing: By consuming exactly 10.5 mm of the optical path, this adapter ensures the flattener is positioned at its design distance for optimal field correction.
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What is the primary purpose of this M92 to M63 Adapter?
This adapter is designed specifically to connect the William Optics FLT91 telescope to the Flat6AIII flattener/reducer. Its primary function is to provide a precise 10.5 mm of spacing, which is required to achieve the correct back focus for a flat imaging field.
How do I use this adapter with my William Optics FLT91 and Flat6AIII?
You thread the M92 male side of the adapter directly onto the focuser of your FLT91 telescope. Then, you thread the Flat6AIII flattener into the M63 female side of the adapter. This configuration establishes the correct mechanical and optical connection between the two components.
Why is the 10.5 mm optical length of this M92 to M63 adapter important?
The 10.5 mm optical length is the most critical specification. Field flatteners must be placed at an exact distance from the telescope's objective to work correctly. This adapter consumes 10.5 mm of the back focus to ensure the Flat6AIII is positioned perfectly relative to the FLT91's focal plane, resulting in sharp stars from edge to edge.
Is this M92 to M63 adapter a universal part for other telescopes?
No, this is a specialized component. While the M92 and M63 threads may be used on other equipment, the 10.5 mm optical length is specifically calculated for the FLT91 and Flat6AIII combination. Using it with other equipment will likely result in incorrect spacing and poor image quality.
Does installing this adapter set the final back focus for my FLT91 imaging train?
No. This adapter correctly spaces the flattener relative to the telescope. You must still add the correct spacers between the flattener and your camera sensor to meet the flattener's own back focus requirement (typically 55 mm, but always check your flattener's manual).
What are the exact thread specifications for this adapter?
The adapter features the following threads:
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Light-In Side (Telescope): M92 male thread
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Light-Out Side (Accessory): M63 female thread
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| Light-In Side Thread |
M92 (male) |
| Light-Out Side Thread |
M63 (female) |
| Optical Length |
10.5 mm |
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