Frequently Asked Questions (FAQ's)

• What type of focuser is best for my scope?
• How important is focusing?
• Why should I consider a Feather Touch ® focuser?
• What type of focuser is best for my refractor or Schmidt-Cassegrain?
• What is the brake option and why do you recommend it?
• How much weight will the 2 inch focuser handle?
• If I own a larger refractor, what focuser do you recommend?
• What length draw tube do I need?

WHAT TYPE OF FOCUSER IS BEST FOR MY SCOPE?

This depends largely on what type of telescope you need a focuser for.  There is a slight distinction whether you are going to use this focuser for a Newtonian or a Refractor/Schmidt Cass type of telescope. For Newtonian type telescopes, where the focuser axis will move in a generally horizontal direction a standard 2 inch focuser will work fine.
If however, the focuser axis will be used in a more vertical direction, as in refractors and Schmidt/Cass telescopes, you may want to consider adding the brake option. Because the motion of the Feather Touch Focuser is so smooth and free moving, it may become necessary to increase the amount of friction that is needed to hold the eyepiece in place. This of course is much more of a problem when the direction of the focuser is working more against gravity. 

FAQ FOR REFRACTOR AND SCHMIDT-CASS TYPE TELESCOPES

HOW IMPORTANT IS FOCUSING?

Next to having great optics, eyepieces and excellent collimation, focusing, in our opinion, is equally as important. In general, focusing needs to be precise and allow positioning of the eyepiece or imaging equipment within .002 inches.
There should be no backlash in the focuser and the focuser should be very free to move. Since our focuser uses a precision 10:1 planetary reduction assembly, this makes focusing extremely easy. Positioning of the draw tube and eyepiece within .0005 inches can easily be achieved. Not only is the positioning of the eyepiece extremely precise but because our focusers are so smooth, the slightest touch on our 10:1 reduction  fine focus knob will allow focusing without shaking of the telescope tube.

WHY SHOULD I CONSIDER A FEATHER TOUCH FOCUSER?

Not only should the focuser provide precision positioning and be easy to use, it should also permit effortless focusing without shaking the telescope. Our 10:1 reduction ratio and the precision of the design make this possible. Since there is virtually “0” backlash, focusing at even very high power is done with ease.
Even though our focusers are slightly more expensive keep in mind that we have designed and built this unit to last a lifetime. You have probably invested much more in your eyepieces and use each of these eyepieces with the focuser, so why not buy a Feather Touch Focuser that will permit the full performance of your telescope?

This depends largely on what type of telescope you plan on using it for. For smaller refractors we would recommend either our 2 inch modified Crayford style with either the 2 or 2.5-inch travel. For larger refractors 125 mm or larger we would recommend our newly introduced 3.5 inch rack and pinion focuser. For Schmidt-Cass type telescopes the 2-inch focuser with either the .8 inch travel or the 1.5-inch travel will work. If the Schmidt-Cass is on a fork type mount the .8 inch travel combined with the shorty adapter will provide clearance between the focuser and the fork mounting in most cases.
The .8 with the shorty adapter was specifically designed for the Meade LX200 so that when the focuser passes through the mount, enough clearance will prevent any potential crashes in the go-to mode. Because the motion of the Feather Touch Focuser is so smooth and free moving, it may become necessary to increase the amount of friction between the pinion and the drawtube in order to hold the eyepiece in place. So for applications using the 2 inch focuser we strongly recommend the brake option.

The brake option was designed to allow users of refractor type applications the ability to gradually increase the friction between the pinion and the drawtube. In our non brake version design we use a thumb screw to lock the pinion shaft and to also increase the amount of drag on the drawtube.
This system however has very little range when trying to control the drag.
The brake consists of an internal leveraged leaf spring that is tightened with a thumbscrew, thereby allowing a much greater control of the drag. The same thumbscrew is also used to lock the pinion shaft.

For refractor applications the same rules apply and generally 5 lbs. of weight is not a problem although this also depends on the length of the draw and where the weight is applied. Since the longer draw tubes increase the leverage and the amount of force on the bearings the weight and the leverage need to be considered in the overall equation.
We have designed our focuser to handle at least 5 lbs. with the 2.5 inch (our longest drawtube) and have not heard of any problems from our customers. Since even the heaviest eyepieces and most imaging equipment does not weigh more than this, the weight limit should not be a problem in most applications. If you have a particular applications where this may be a concern please do not hesitate to consult us on your application.

IF I OWN A LARGER REFRACTOR WHAT FOCUSER DO YOU RECOMMEND?

• It uses a wide fine pitch rack and pinion that is coupled to a 9:1 fine focus reduction assembly similar to our smaller 2 inch focusers giving you the same excellent focusing control as our 2 inch models.
  
  
• The drawtube glides on three stainless steel straps that mate with Teflon surfaces to provide very tight yet extremely smooth motion. Using this type of design eliminates the need for grease between the drawtube and housing. A greaseless draw tube prevents the attraction of dirt that may eventually cause problems between these surfaces.
  
  
• External adjustment screws can control the tension of the drawtube in the housing thereby allowing the tension to be matched to the equipment that is generally used.
  
  
• An additional adjustment/drawtube-locking knob can be used for on the fly adjustment when needed. This same adjustment nut can also be used for additional tightening of the drawtube to prevent any movement of the drawtube relative to the housing during long exposures.
  
  
• The drawtube has internally machined baffles that reduce internal reflections.
  
  
• Each rack and pinion set is matched and burnished in to provide very smooth engagement between the rack and the pinion.
  
  
• The pinions are machined from hardened stainless steel for long life and reliability and the entire pinion block assembly is adjusted and locked in place reducing and virtually eliminating any backlash between the rack and the pinion.
  
  
• The large drawtube allows a generous 4.5 inches of travel without vignetting at f5 or larger.
  
  
• The entire focuser can be rotated relative to the telescope tube thereby making orientation of the focus knobs convenient. This also allows the positioning of objects and the location of guide stars much easier. The focuser body is located in a tube adapter ring and locked in place with the focuser-locking ring. When this ring is turned and loosened slightly the entire assembly can be rotated. Once the desired position is reached the focuser locking ring is tightened thereby locking the entire assembly.
  
  
• The end of the draw tube is fitted with a 2 inch collet attachment for 2 inch eyepieces. This collet attachment locks onto the eyepieces using a plastic sleeve that is compressed This eliminates the use of thumb screw and always assures that the eyepiece is perfectly aligned.

This depends largely on the your eyepieces and the equipment that will be used on the focuser. In general the 2 inch focuser draw tube seems to work well for most applications. One of the best ways of determining the needed travel is to measure the position of each of your eyepieces on an existing telescope focuser relative to a fixed location on the existing focuser. Measure the location for each eyepiece and combinations of eyepieces with a scale or other suitable means. From these locations determine the difference between the minimum to maximum distance. The resulting distance will be the minimum travel you would need.
Keep in mind if a 35 mm camera or CCD camera is used you will need to make sure that the focal plane can also be reached. It is also important to keep in mind that our focuser draw tube will retract .2 inches into the housing of the focuser body thereby preventing the use of the extra .2 inches of travel.
This extra in-travel was originally intended to permit improved performance for Newtonian applications where position of the eyepiece relative to the secondary plays an important role in the size of the secondary and the overall performance of the telescope. Therefore this extra .2 inches of  in-travel will only work for 1.25 eyepieces and will interfere with eyepieces or equipment that will not clear the bearings and housing.