Dual-Speed Crayford Focuser with Linear Track Bearing

1.25" Adapter

Accessory lock thumbscrew

Brass compression ring

Coarse focus wheel

Focus lock thumbscrew

Accessory lock thumbscrew

2" Collar

Accessory lock thumbscrew

10:1 Fine focus wheel

Drawtube tensioning

thumbscrew

Coarse focus wheel

Figure 2. The dual-speed 2" Crayford-type linear bearing focuser

are M6. It is likely that only the center hole will be needed to attach the rings to a dovetail plate for your mount or for your guide scope assembly.

Balancing the 8" f/4.0 Newtonian Astrograph is achieved by sliding the dovetail mounting plate (sold separately) for- ward or backward within the mount’s dovetail saddle. You can also move the telescope forward or backward within the tube rings. The tube rings offer the most adjustment range. Loosen the tube ring clamps slightly and slide the telescope tube forward or backward as needed to reach optimum bal- ance, then retighten the tube ring clamps. Rotating the tele- scope to achieve a comfortable eyepiece or camera angle is done in the same fashion. Simply loosen the tube ring clamps just enough to allow the optical tube to rotate within the tube rings. Retighten the tube ring clamps securely once you have reached the desired eyepiece or camera orientation.

Dual-Speed Crayford Focuser with Linear Track Bearing

The 8" f/4.0 Newtonian Astrograph features a machined alu- minum, 2" dual-speed Crayford-type focuser (Figure 2) that incorporates a linear track bearing design. The linear bear- ing eliminates drawtube play and enables support of heavier loads without slippage. If the drawtube does slip under the weight of your imaging system or heavy visual accessories, simply increase the drawtube tension by gently tightening the drawtube tensioning thumbscrew as needed.

The smooth focus motion and fine-focus wheel allow preci- sion adjustments for critical focusing of eyepieces and camer- as. Once you have reached focus, you can lock the drawtube in place by tightening the focus lock thumbscrew.

The focuser drawtube has 50mm of travel and English and metric hash marks, which allow you to note the drawtube position at the precise focus point so you can return to it when you need to.