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Starlight Instruments 3.5" End Cap w/ 3.5" Compression Ring Opening
The Starlight Instruments 3.5" End Cap provides a 3.5" compression ring opening for 3.5" accessories on your Feather Touch 3.5" focuser. It suits imaging trains built around a 3.5" optical path.
A Secure Grip for Your 3.5" Imaging Train
Designed specifically for the Starlight Instruments FTF35xx series of 3.5" focusers, this end cap allows you to use accessories with a standard 3.5" slip-fit barrel. It provides the robust mechanical interface needed to support large format cameras, heavy eyepiece turrets, or wide-field correctors without introducing flexure or instability into your optical train.
Compression Ring Hold for 3.5" Accessories
A compression ring grips around the accessory barrel instead of pressing a single screw against it, so 3.5" accessories slide in and out without threading.
Choosing Your 3.5" Connection: Compression Ring vs. Threaded End Caps
A direct-threaded connection offers the most rigid possible interface, ideal for dedicated imaging rigs that are rarely disassembled. However, this compression ring end cap provides superior convenience for visual observers or imagers who frequently swap accessories like correctors, extenders, or cameras. It allows for quick changes in the dark without the risk of cross-threading, making it the more flexible choice for dynamic observing sessions.
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Which Starlight Instruments focusers is the 3.5" Compression Ring End Cap compatible with?
This end cap is designed exclusively for the Starlight Instruments FTF35xx series of 3.5" Feather Touch focusers. It attaches to the drawtube to allow the use of 3.5" slip-fit accessories.
I use a large, heavy 3.5" corrector with my imaging camera on an FTF3545 focuser. Is this end cap secure enough?
This end cap has no stated load rating. For a heavy imaging train that stays assembled, a threaded end cap gives the most secure connection.
Can I adjust for tilt with the Starlight Instruments 3.5" Compression Ring End Cap?
Starlight does not say for this model. Its 3.5" focuser manual notes that most of its end caps have 3 set screws on the face that allow collimation (tilt) adjustment with a 1/16 hex key.
When should I choose this 3.5" Compression Ring End Cap over a threaded version?
Choose the 3.5" Compression Ring End Cap for flexibility and speed. It's ideal if you:
- Frequently switch between visual observing and imaging.
- Use multiple accessories (e.g., different cameras, correctors) during a session.
- Want to avoid the hassle and potential for cross-threading in the dark.
Choose a threaded end cap for a semi-permanent, maximally rigid connection in a dedicated imaging setup that is rarely changed.
I'm setting up for a night of visual observing with a large refractor and several 3.5" accessories. How does this end cap help?
This end cap dramatically simplifies your workflow. Instead of carefully threading and unthreading heavy, expensive accessories in the dark, you can simply loosen the compression ring, slide one accessory out, and slide the next one in. This makes it fast and safe to switch between a low-power eyepiece for finding objects and a high-power setup for detailed views.
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| Compatibility |
Starlight Instruments 3.5" Feather Touch Focusers (FTF35xx Series) |
| Accessory Mount |
3.5" compression ring opening |
| Kind |
End cap, 3.5" compression ring |
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Starlight Instruments 3.5" End Cap w/ 3.5" Compression Ring Opening
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- Starlight Instruments 2-Year Warranty
