ASToptics 2 mm M48 Aluminium Spacer Ring
When building an optical train, extension tubes do not always close the gap precisely. Sometimes just a small distance remains - enough to prevent correct focus or an accurate backfocus calculation. The ASToptics 2 mm aluminium spacer ring solves exactly that problem. It looks like a simple part, but in practice it determines whether your entire optical train works correctly or not. Add the ring to your setup and reach the precise spacing you need.
Compatible with standard 2″ filter thread
The M48x0.75 spacer ring is compatible with the standard 2″ filter thread found on cameras, filter drawers, field flatteners, and other accessories. The aluminium construction keeps weight low while maintaining solid rigidity - the ring does not deform under repeated tightening and holds its exact dimensions over time. The finish matches the standard used across other ASToptics components, so the ring integrates cleanly into a visually and functionally unified setup.
Why backfocus spacing matters in astrophotography
Using spacer rings is common practice in astrophotography, where every tenth of a millimetre of backfocus distance counts. Precise spacing in the optical train directly affects star quality at the edges of your image. Incorrect spacing causes coma or astigmatism - problems that no amount of post-processing can fix. At 2 mm, this ring covers the fine corrections where an extension tube would be too coarse a tool. It also works well alongside a set of rings in different thicknesses, letting you combine them to reach any spacing you need.
Key features
- Thickness: 2 mm
- Thread: M48x0.75 - standard 2″ filter thread
- Material: aluminium
- Low weight, high rigidity
- Precise dimensions maintained under repeated use
- Finish consistent with other ASToptics components
- Compatible with cameras, filter drawers, field flatteners, and related accessories
Technical specifications
| Parameter |
Value |
| Thickness |
2 mm |
| Thread |
M48x0.75 |
| Filter thread compatibility |
2″ |
| Material |
Aluminium |
| Brand |
ASToptics |
Who is this spacer ring for?
This ring is ideal for astrophotographers who work with camera and filter systems on a 2″ optical train and need fine control over backfocus distance. It suits both beginners building their first imaging setup and experienced observers who want to complete a set of spacers in various thicknesses for flexible configuration.
