TS Optics Monorail M90x1 2″ 1:10 focuser
If you have ever been frustrated by a slight focus shift when tightening the lock screw, or by a heavier eyepiece causing noticeable tilt of the drawtube, then you know exactly why TS Optics developed the Monorail focuser series. This precision Crayford-style focuser replaces the classic ball bearings with a solid stainless steel monorail - and this is where the difference begins, one you will notice the very first time you touch it.
Why monorail instead of classic ball bearings?
Traditional Crayford focusers rely on contact between the drawtube and small ball bearings. This works well - until you attach a heavier eyepiece, a binoviewer, or a CCD camera. In the Monorail M90, the guiding is achieved using a robust stainless steel monorail rail, which provides precise and rigid support of the drawtube along its entire travel path. The result is zero tilt even under full load and no focus shift when locking - something that tends to be an annoying routine with cheaper focusers simply does not happen here.
A load capacity of up to 4 kg means the focuser can handle even the most demanding combinations of eyepiece, filter wheel and camera without any issues.
Dual-speed 1:10 control for precise focusing
The focuser is equipped with a dual-speed system with a 1:10 reduction ratio, which astronomers know well as one of the most beneficial upgrades available. Coarse focusing is done with the standard knob, while fine tuning is performed using the reduction wheel with ten times slower movement. At high magnifications, during planetary observation or astrophotography, you will appreciate every micrometer of control - and the Monorail M90 delivers exactly that. The drawtube movement is silky smooth throughout the entire 50 mm travel, with no sticking or backlash.
Compatibility and key specifications
The focuser connects via a standard M90x1 thread, which is common on many refractors of medium and larger apertures, as well as Newtonians with a suitable adapter. Included is a drawtube lock ring and a universal eyepiece holder compatible with both 1.25″ and 2″ diameters - so there is no need to purchase a separate reducer for smaller eyepiece accessories.
| Parameter |
Value |
| Connection thread |
M90x1 |
| Eyepiece holder |
2″ (with 1.25″ compatibility) |
| Reduction ratio |
1:10 dual-speed |
| Drawtube travel |
50 mm |
| Load capacity |
up to 4 kg |
| Optical length |
over 90 mm |
| Drawtube guide |
stainless steel monorail |
Important note for astrophotography
The optical length of the focuser exceeds 90 mm, which is an important parameter when calculating the back-focus distance of your optical system - particularly relevant for photographic applications.
Who is this focuser for?
The Monorail M90x1 is an excellent choice for anyone who wants to get the most out of their telescope - whether for visual observation with demanding eyepiece systems, or during long imaging sessions where the reliability and rigidity of the focuser directly affect the quality of the final images. Installation is straightforward and the improvement is immediately noticeable.
- Visual observers using heavy eyepieces or binoviewers
- Astrophotographers requiring zero image shift and maximum stability
- Users of refractors and Newtonians with M90x1 connection
- Anyone upgrading from a standard focuser to a precision solution
