Baader Diamond Steeltrack 2" Focuser for Refractors

The Diamond Steeltrack Drive

True diamonds form its micro-geared, high-precision drive, and in comparison to conventional Crayford or rack-and-pinion drives this movement has zero backlash, zero cogging and zero flexure. The bearing system uses unbreakable instrument-grade roller bearings instead of simpler ball bearings, with no Teflon pads anywhere, running on ultra-hard subzero-coated bearing races that are precision milled and much harder than anodizing or stainless steel.

The 1:10 stainless-steel fine-focus mechanism moves the drawtube about 2 mm per turn of the fine knob, against about 22 mm per turn of the coarse knob. The detachable drive block is reversible for right- or left-hand fine-focus operation: remove the four marked screws with a 2.5 mm Allen wrench, rotate the block by 180°, refit the screws carefully, then check the alignment and that the focuser runs as smoothly as before.

80 mm Travel, Load Setting and Drawtube

The BDS-RT provides a generous 80 mm of focus travel, marked by an engraved 1 mm index scale for repeatable measurements. The focuser is rotatable. By factory default the pressure screw, which sets the contact pressure between the diamond-coated axis and the steel plate, holds up to 6 kg of lifting force; this setting was chosen for photographic use. You can tighten it further, but the focuser will then run less smoothly, or loosen it for visual use to make it run even more smoothly. The focusers are also rigid and slip-proof without a locking screw pressing on the tube or drive plate, so motor focusers can be used at any time without tipping the image plane, and the zero-shift locking knob stops any movement without affecting the optical axis adjustment.

The drawtube itself is built for rigidity. Each of its roller bearings is individually adjustable for precise alignment of the mechanical and optical axes, and they run on ultra-hard subzero-coated bearing races. The oversized 55 mm tube has anti-reflection knife-edge baffles to prevent vignetting. Two auxiliary threads (M60x1 and M55) are cut into the focusing tube for dedicated field flatteners or focal reducers/correctors.

Telescope-Side Connections: M68x1 Thread and S88 Dovetail

The BDS-RT for Refractors offers a robust and adaptable mounting system. It ships with an M68 x 1 male telescope adapter. Removing it by loosening six M5 screws gives access to the 88 x 7 mm dovetail, which takes various telescope adapters.

Adapters are available or under development to fit a wide variety of refractor telescopes. The housing also has five M5 threads, covered by screws, for mounting accessories: removing two of them lets you fit the Baader Standard Finder Base (#2457000), or the MQR III or MQR IV finder brackets (#2457020 / #2457030), which include it.

Eyepiece-Side Connections: A 55 mm Aperture with an S58 Dovetail

The 2" eyepiece clamp with hardened bronze clamp ring (12.5 mm long) is included as standard. The S58 dovetail ring clamp built into the focusing tube accepts optional T-2, M48, M68 and other S58 direct-thread adapters, so accessories and cameras can be threaded on without the 2" clamp, and Baader offers an optional 2" S58 ClickLock clamp (#2956258), which adds 16 mm. The integrated 2" clamp comes off after loosening its six M2.5 headless set screws with the included 1.3 mm Allen wrench.

For the most rigid imaging setups, you can remove the 2" clamp and attach optional S58 adapters directly to the drawtube. Options include the BDS T-2 (#2957202), M48 (#2957204) and M68 adapters for direct thread connection of accessories and cameras without the 2" clamp.

Height and Weight

The minimum height is 78 mm as supplied with the 2" clamp, 65 mm with an optional S58 to M68/M68i/M48/T-2 direct adapter, and 89 mm with the optional S58 ClickLock clamp. The design is the shortest possible mechanical layout that balances focuser height (backfocus) against rigidity. Net weight is 1.11 kg.

Optional Steeldrive II Motor Focuser

All Diamond Steeltrack focusers carry a dovetail for the optional temperature-compensating Baader Steeldrive II motor focuser with controller (#2957165); a mounting instruction is included with each Steeldrive II.

Because the drive needs no locking screw pressing on the tube or drive plate, motor focusers can be used at any time without tipping the image plane.

Aligning the Drawtube

BDS focusers are unique in that they can be fine-aligned (collimated), so critical users can square the focuser to the optical axis; this is particularly useful for imagers who need sharp stars out to all corners. Every BDS is aligned at the factory to be square to its mounting base, and most users will find this sufficient with most commercially produced telescopes, particularly visual observers, for whom the procedure is not recommended. The adjustment works through bearing adjustment screws around a pivot point on the bearing block; read the instructions completely first, make only small adjustments, and attach no heavy accessories during the first attempt, since the drawtube is loose and could slip.

Use a laser collimator such as the Baader Mark III LaserColli (#2450343) to monitor the adjustment, and metric hex keys of 2, 2.5 and 4 mm. Overtightening screws can damage bearings and may void the warranty.