A good focuser is of the utmost importance to the visual observer as well as the astrophotographer. After all, what use are the best optics in the world if you can’t bring them to pin sharp focus easily and effectively.
This dual speed Crayford from Skywatcher is a big step up from the rack & pinion gear based focusers that are sold on the majority of basic budget to mid range telescopes. To briefly explain, a rack & pinion focuser uses gears to move the draw tube up and down, this can result is a series of unpleasant phenomena. Backlash can occur, when the focusing direction is changed and the gears take a moment to catch up, this results in an absence of focus travel when turning the focusing knob Slop can sometimes occur when the draw tube of the focuser isn’t secured properly within the telescope, resulting in a draw tube that is free to wiggle and move around, this results in uneven focus as well as image shift (the object you’re observing goes flying out of the field of view).
Crayford focusers use a smooth circular wheel that pins the draw tube to the telescopic tube, using constant pressure to eliminate slop and as there are no gears there is no problem with backlash either.
£130 may sound expensive for a focuser but this is actually one of the lower cost entries available. There are numerous aspects that make this Crayford special not least of all it’s appealing price tag. Not only is this Crayford cheap but it’s extremely well made. Solidly built and reassuringly weighty.
There are a series of nice little features present, the draw tube is marked incrementally in centimetres which makes it easier to remember perfect focus position. Once perfect focus has been obtained by rotating the rubber knurled adjusters of either the standard focusing nob or the more sensitive 10:1 focusing knob you can lock the focus tube into place with a single silver (read also: silver facts) thumb screw. This is especially useful if you are loading a lot of weight on the focuser (a heavy eyepiece, barlow and camera combination for example),
That does bring us round to one small area of disappointment, being the draw tube of this focuser cannot take a huge amount of weight. This won’t be a problem to your average observer/photographer but can become bothersome when using a lot of heavy equipment. There is a thumb screw that adjusts the tension of the focuser and so allows heavier loads but this comes at the price of making the focuser stiffer and harder to use.
-The Pros-
Smooth action including a 10:1 focus adjuster for fine adjustments. Length measurements printed on the tube not only look stylish but have an important practical function of making it easier to find optimum focus quickly and consistently. The focuser is fully rotatable meaning no matter how your scope is positioned you can reach the rugged rubber nobs easily, the more comfortable the observer whilst focusing the better grip and therefore better control is that can be achieved. Also the focuser is cheap to buy but not cheaply made, the unit feels solid and well built.
-The Cons-
May not be suitable for use with heavier equipment. The focus tube can move about once it’s weight thresh hold has been passed. Allen Keys will have to be used to install the unit, there are two different sized Allen keys (or hex keys) that will be needed, to avoid disappointment it may be best to email Skywatcher directly, they will be happy to inform you of the appropriate tools that will be required for successful installation.
