Telescope Focusers

Whether you intend to use it for visual astronomy or astrophotography, your telescope needs a focuser. That focuser will be of the utmost importance in your system as a whole, and should be chosen carefully to fit your specific needs, taking into consideration such factors as how precisely focused you need your image and what kind of weight you have room for in your setup. These are all questions that OPT is happy to help answer, just like every other step in the fun and engaging process of purchasing your next telescope. The focuser used with a telescope is definitely of the utmost importance, as it is required to bring objects into the sharpest level of clarity and detail possible. A good focuser can drastically improve the usability of your telescope, while a poor one can ruin a night of imaging and make it impossible to find anything at all. This is why here at OPT, we do our best to stock only the best options for focusers, and to guide you to the focuser that best fits your telescope and goals. 

 

                                                                                                                                 

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Whether you intend to use it for visual astronomy or astrophotography, your telescope needs a focuser. That focuser will be of the utmost importance in your system as a whole, and should be chosen carefully to fit your specific needs, taking into consideration such factors as how precisely focused you need your image and what kind of weight you have room for in your setup. These are all questions that OPT is happy to help answer, just like every other step in the fun and engaging process of purchasing your next telescope. The focuser used with a telescope is definitely of the utmost importance, as it is required to bring objects into the sharpest level of clarity and detail possible. A good focuser can drastically improve the usability of your telescope, while a poor one can ruin a night of imaging and make it impossible to find anything at all. This is why here at OPT, we do our best to stock only the best options for focusers, and to guide you to the focuser that best fits your telescope and goals.

Focusers can be broken down into two basic categories based on design: rack and pinion and Crayford.  Within each of these categories are variations on the design. 

The most common telescope focuser of all is the rack and pinion focuser.  It gets its name from the rack of small gear teeth which run along the spine of the drawtube which move it in and out using pinion gears connected to the focus knob.  This "in and out" motion is what brings the eyepiece to the focal point.  Different eyepieces have different focal points, so there's definitely a need for traveling distance.  A well-built rack and pinion focuser will last the lifetime of the telescope.  A variation on the rack and pinion design is the microfocuser.   Using the same principle as the rack and pinion, the microfocuser, like the popular FeatherTouch, has an additional set of even smaller teeth on the rack to allow for finer adjustment.

Unlike the rack and pinion, the Crayford does not use gears to move the drawtube.  Instead, the tube is moved by a roller and is carried along by user adjustable pressure bearings placed at even intervals around the focus drawtube.  The design helps eliminate backlash issues often seen on inexpensive rack and pinion designs.  Like the microfocuser, the Crayford also has two "speeds" as a standard - one for coarse adjustment and the other for fine focus.  A variation on the Crayford that is often confused for a different design altogether is the Rear Cell, or SCT focuser.  The SCT focuser, most commonly found on Schmidt Cassegrain telescopes, leaves the eyepiece stationary while moving the primary mirror to bring objects to focus.  Crayford focusers also run the gambit on versatility.  They can be controlled digitally, sense and account for temperature differences, carry unbelievable weight loads and even focus right down in the "nano" level.  We offer every type and style you can possibly want.

There is also a plethora of focusing aids, which are not complete focusing systems.  Electronic meters and motors can be added to your exisiting focuser to allow for a higher degree of accuracy or to bring your hand away from the focusing knob which helps eliminate vibration problems.  There are also focusing aids that will help you reach a better focus with the focuser you already have.  These range from simple tools which allows the user to check alignment, camera adjustment and focus through three ports to parfocalizing rings which essentially stops the drawtube at a precise focal point.