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.
How does the 3.5" Compression Ring End Cap prevent damage to my eyepieces?
The end cap features a soft brass compression ring. Brass is softer than the anodized aluminum used for most accessory barrels. When you tighten the thumbscrews, this ring gently grips the barrel across a wide surface area, preventing the scratches and gouges that can be caused by direct contact with a steel set screw.
I use a large, heavy 3.5" corrector with my imaging camera on an FTF3545 focuser. Is this end cap secure enough?
Yes. The 3.5" compression ring system is engineered to hold heavy loads securely. The wide contact area of the ring provides significant friction, and the large thumbscrews allow you to apply firm pressure, ensuring your heavy imaging train remains locked in place without flexure.
Can I adjust for tilt with the Starlight Instruments 3.5" Compression Ring End Cap?
Yes. Like most Starlight Instruments end caps, this model typically includes three small set screws around its circumference. These screws allow for fine-tuned collimation adjustments, enabling you to eliminate any optical tilt between the focuser and your camera sensor or eyepiece.
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 thumbscrews, 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.
