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How Do I Choose the Best Telescope Focuser?

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  • Written By: Mal Baxter
  • Edited By: Daniel Lindley
  • Last Modified Date: 09 September 2016
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    2003-2016
    Conjecture Corporation
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Stargazers and telescope aficionados get a handle on the stars using telescope focuser components. Numerous manufacturers offer a wide array of telescope focuser products. These provide varied designs and capabilities to enhance focus for telescope imaging. Products from low to high tech can perform with improved precision, speed, and ease over factory stock components. If you want to select the best telescope focuser, know the basic focusing systems for your type of telescope, select among several focuser configurations, and decide how high-tech you want to go.

Two primary types of focusing systems exist for telescopes: those with internal or external focusing mechanisms. Newtonian and refracting telescopes rely on a sliding drawtube that moves with the rotation of a knob. These telescopes usually work with rack and pinion style focusers. Other types of telescopes, such as the Schmidt-Cassegrain and Maksutov-Cassegrain varieties, adjust internal primary mirrors by turning focus knobs. Both sorts shift the granularity of adjustment to dial in precise magnifications.

Telescope focuser products include rack and pinion and micro-focuser designs. Rack and pinion products use a gear system to extend drawtubes. Micro focuser types perform a similar action but with smaller gears for fine tuning. Some products are called helical focusers, and provide screw turn action for these scopes.

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Crayford focusers stand in contrast to the rack and pinion varieties. These roll smoothly on pressure bearings, typically with coarse and fine adjustments. Optimally designed for heavier telescopes, they generally operate on scopes with internal mirror focusing adjustments. If you require high precision, perhaps with digital control, these focusers can offer more exacting performance down to atomic scales.

Electric and motorized focusers bring touch-sensitive precision to their operation. Offering variable speeds, these types may nullify any vibration from manual handling. In addition to telescope focuser products, other accessories enhance precision and functionality. Some might include parfocalizing rings, and other accessories that aid with alignment and adjustment.

The range of speeds offered by telescope focuser designs may help bring your choice into greater relief. Some may be constructed for smoother operation, while others may be designed with ergonomic or tactile characteristics. That is, they may be more knobby or intuitive to the touch, and require less distraction from viewing. As always, the weight of the scope will affect the performance of its focuser, and should factor into your decision.

How well mechanisms brake is an additional element when deciding which telescope focuser is best for your needs. Products may offer manual or automatic braking. Some feature precision stops, while others may experience a slight braking drift. Depending on how high tech you want to go, the right focuser could mean the difference between wishing on and catching that star.

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