Best 2-Inch Extension Tubes for Telescopes: Extend Reach for Focus and Astrophotography
Extension tubes add back travel to your telescope’s focuser, helping you achieve precise focus and correct image scale for both terrestrial viewing and astrophotography. The following selections are 2-inch (2″) extension tubes that fit standard focusers, accept 2″ eyepieces, and include features like locking thumbscrews and brass compression rings to prevent marring. This guide highlights five options that balance length, compatibility, and build quality for American readers seeking reliable performance.
The table below summarizes five compatible 2″ extension tubes, focusing on common lengths and key features to help compare at a glance.
| Product | Brand | Length (mm) | Notable Features | |
|---|---|---|---|---|
| SV158 Extension Tube (45mm) | SVBONY | 45 | 2″ focusers, 2″ eyepieces | Back travel, brass compression ring, locking thumbscrews |
| SV158 Extension Tube (55mm) | SVBONY | 55 | 2″ focusers, 2″ eyepieces | Back travel, two thumbscrews, accepts 2″ filters |
| Astronamia 35mm Tube | Astromania | 35 | 2″ focusers, 2″ eyepieces | Brass compression ring, two locking thumbscrews |
| Astronamia 50mm Tube | Astromania | 50 | 2″ focusers, 2″ eyepieces | Back travel, two thumbscrews, 2″ filter threads |
| Alstar 80mm Tube | A ALSTAR | 80 | 2″ focusers, 2″ eyepieces | Back travel, brass compression ring, two locking thumbscrews |
SVBONY SV158 45mm Extension Tube
The 45mm SV158 extension tube provides extra focuser back travel essential for astrophotography and precise focus. It is designed for standard 2″ telescope focusers and accepts 2″ eyepieces or accessories. A brass compression ring helps prevent marring of telescope accessories, and locking thumbscrews securely hold inserted components, contributing to stable imaging and viewing setups.
SVBONY SV158 55mm Extension Tube
The 55mm SV158 tube adds extension to achieve the correct image scale, beneficial for short-range terrestrial viewing and astrophotography. It includes two locking thumbscrews for secure attachment and is threaded for 2″ telescope eyepiece filters. This extended length fits 2″ focusers while maintaining compatibility with standard 2″ accessories.
Astromania 35mm 2-Inch Extension Tube
The 35mm Astromania extension tube fits 2″ focusers and accepts 2″ eyepieces or accessories. It features two locking thumbscrews and a brass compression ring to prevent marring. It provides extra focuser back travel, supporting short-range terrestrial viewing and astrophotography workflows that require precise spacing.
Astromania 50mm 2-Inch Extension Tube
The 50mm extension tube from Astromania provides additional back travel for focus adjustments, best used when specific eyepieces or reducers require spacing changes. It keeps 2″ focusers compatible with standard 2″ eyepieces and accessories, and includes two locking thumbscrews plus a brass compression ring to protect equipment surfaces.
Alstar 80mm Telescope Extension Tube
The Alstar 80mm extension tube adds substantial back travel for challenging focus scenarios. It is designed for 2″ focusers and accepts 2″ eyepieces or accessories. The brass compression ring and locking thumbscrews help guard against marring and ensure a secure fit during imaging or observing sessions.
Buying Guide
- Length needs: Choose length based on focal length, eyepiece type, and whether you need more back focus for reducers or field flatteners. Longer tubes provide more adjustment but add bulk.
- Thread compatibility: Ensure the tube supports 2″ eyepieces and is compatible with 2″ filters if you plan to use them. Some tubes are optimized for astrophotography with filter threading.
- Retention features: Look for locking thumbscrews and a brass compression ring to protect accessories from scratches and to maintain stability during use.
- Build quality: Brass components and sturdy housings generally offer better durability and a smoother focusing experience than cheaper plastics.
- Mount and scope compatibility: Verify that the tube’s male/female threads align with your telescope’s focuser and any attached adapters or reducers.
- Applications: Use extension tubes for terrestrial viewing to improve image scale, or for astrophotography to achieve exact spacing with reducers, correctors, or field problems.
- Budget considerations: For hobbyist setups, mid-length tubes with locking screws offer a balance of flexibility and cost without compromising build quality.