Baader Diamond Steeltrack 2" Focuser for Newtonians

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.

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; Baader chose this setting 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. Baader adds that the focusers are 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.

40 mm Travel, 1:10 Fine Focus and Rotation

The BDS-NT has 40 mm of focus travel and an engraved index scale from 0 to 40 mm in 1 mm steps. 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.

The focuser can be removed from or rotated on the VersaBase by loosening the eight M3 hex screws (two on each side), which need a 1.5 mm Allen wrench (not included).

Telescope Connection: S88 Dovetail and VersaBase

The BDS-NT ships with the Baader VersaBase, which fits most tube diameters of 200 mm and larger. On the telescope side the focuser has an 88 x 5 mm (S88) dovetail for various telescope adapters, reached by removing the VersaBase. An optional flat base plate (96 x 96 mm, #2957231) is also available, with which the weight is 900 g.

Baader's mounting sequence on an 8" Newtonian: remove the current focuser; remove the BDS-NT from the VersaBase by opening the eight hex screws; use the old screws and nuts to centre the VersaBase plate; drill four new 5 mm holes, straight to the tube centre, in the middle of each elongated cutout; attach the radial sliding bolts from the inside out; remove the old screws; then attach the focuser in the preferred position and tighten the eight hex screws. On an 8" Newtonian the two 1.5 mm strip shims are not needed; for other tube diameters they go between the tube and the VersaBase and give up to 4 mm of height.

Eyepiece Connection: S58 Dovetail, M55 Threads, and 2-inch Clamp

The eyepiece side of the BDS-NT offers a multi-faceted connection system for maximum flexibility. 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 an optional 2" S58 ClickLock clamp (#2956258) is available, which adds 16 mm. The drawtube has an oversized 55 mm clear inner diameter with anti-reflection knife-edge baffles to prevent vignetting.

For direct-threaded imaging trains, the drawtube incorporates several connection options:

• S58 Dovetail: Built into the focusing tube, for optional T-2 (#2957202), M48 (#2957204) and M68 direct-thread adapters and the S58 ClickLock clamp (#2956258). They are fitted after loosening the six M2.5 headless set screws of the integrated 2" clamp with the included 1.3 mm Allen wrench.
• M55x0.75 Thread: An auxiliary thread cut into the focusing tube for dedicated field flatteners or focal reducers/correctors.
• M60x1 Thread: The second auxiliary thread for the same purpose.

Height and Weight

The minimum height is 63 mm as supplied with the 2" clamp, 50 mm with an optional S58 to M68/M68i/M48/T-2 direct adapter, and 81 mm with the optional S58 ClickLock clamp. A recessed area allows very short 1.25" reducers, such as the Baader Pushfix adapter (#2408151) with 1 mm optical height. The net weight is 1.01 kg.

The design is the shortest possible mechanical layout that balances focuser height (backfocus) against rigidity.

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.