Telescope Mounting and Focuser Base Plate Choices:
This focuser can be ordered with a choice of one of several base plates for your telescope (see the drop-down list above for available choices that are in stock). Please note that we are unable to recommend a specific base plate for your telescope - there is no standardization in the industry and we do not have the hole mounting specification for most scopes. You will therefore need to compare our base plate specifications with the tube/focuser specifications on your telescope and make a choice yourself. For detailed specifications and hole spacing of the available base plates, please click here.
Besides the base plate details, you must also consider the following:
(1) Make sure that the hole cut out in your telescope tube is larger than the outside diameter of the focuser drawtube. This is often an issue for telescopes smaller than 8" in aperture or for those with a smaller 1.25" focuser. However, also make sure that the current cutout is not so large that it gets in the way of the screw holes.
(2) Compare the minimum and maximum heights of the focuser (provided below) with those of your current focuser. This will indicate whether you will be able to reach focus with your eyepieces and accessories, or whether you might need extension tubes.
This very high quality, single-speed Crayford focuser for reflector telescopes from Guan Sheng Optical (GSO) is a joy to use. You will wonder how you ever lived without it once you install it! It will greatly aid in achieving precise focus for visual observations and astrophotography and you will experience very smooth and precisely controlled focuser motion with zero backlash and zero image shift.
CNC machined from aluminum and anodized black, this focuser comes with a base plate to attach to your reflector telescope. The inner drawtube glides on 4 precision bearings and a roller shaft and provides 35mm of focus travel. The inner barrel is baffled and painted a flat black to minimize reflections for maximum contrast.
The 2" focuser barrel features a brass compression ring so your eyepieces and other accessories will not be marred by the set-screw. Also included is a 1.25"-2" adapter with brass compression rings that is threaded to accept standard 2" filters.
The focuser also has two large thumbscrews. The thumbscrew on the telescope side can be used to lock the focuser, allowing the use of heavy accessories or cameras without fear or slippage or losing focus. The other thumbscrew on the eyepiece end can be used to adjust the tension of the focuser to achieve a focusing "feel" that you like. At the easiest (lightest) setting, the focuser moves extremely smoothly. At tighter settings, you can still use heavier accessories without sacrificing much of the smooth focuser action. GSO's rated load capacity for their Crayford focusers is a little less than 6 lbs (2.7 kgs).
Focuser Specifications (With 8"/10" Base Plate):
• Minimum focuser height (with 1.25" adapter) = 3.23" (82mm)
• Maximum focuser height (with 1.25" adapter) = 4.61" (117mm)
• Minimum focuser height (without 1.25" adapter) = 2.83" (72mm)
• Maximum focuser height (without 1.25" adapter) = 4.21" (107mm)
• Tube travel = 1.38" (35mm)
• Focuser weight (with 1.25" adapter) = 1lb-6.7oz (643gm)
• Focus knob diameter = 1.57" (40mm)
• Microfocus knob diameter = N/A
• Maximum outer drawtube diameter = 3.15" (80mm)
• Millimeter markings on focuser drawtube: No
• Rotatable: No (But body can be rotated by loosening two allen screws that connect the focuser to the base plate)
• Dust plug: One 1.25" dust plug included
Please note: Most GSO Crayford focusers have or will soon develop two bearing marks/lines on the upper side of the drawtube. This is caused by wear on the barrel anodizing where is makes contact with the roller bearings. In some focusers, you have to look hard to find these marks. In others, it is very prominent, even for brand new items received from GSO. This does not indicate a defective or used product and is essentially just cosmetic.
• User Manual: Optimizing the Performance of your GSO Crayford Focuser