Credit: AgenaAstro

New from GSO! This high quality, single-speed 1.25" 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. 

 

Credit: AgenaAstro

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 47mm of focus travel. The inner barrel is baffled and painted a flat black to minimize reflections for maximum contrast.

 

Credit: AgenaAstro

 

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 very smoothly. At tighter settings, you can still use heavier accessories without sacrificing much of the smooth focuser action.

 

Credit: AgenaAstro

 

Focuser Specifications (With 176mm Base Plate):
• Minimum focuser height = 3.01" (77mm)
• Maximum focuser height = 4.88" (124mm)
• Tube travel = 1.86" (47mm)
• Focuser weight = 14oz (397gm)
• Focus knob diameter = 1.24" (31.6mm)
• Microfocus knob diameter = N/A
• Outer drawtube diameter (on telescope side - your telescope tube cutout must exceed this) = 1.83" (46.6mm)
• 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
• Brass compression rings: No

 

176mm Base Plate Specifications:

- Base plate curve diameter: 6.93" (176mm)
- Base plate dimensions: 2.8" x 2.8" (71mm x 71mm)
- Hole Spacing (center-to-center along telescope tube/optical axis): 57mm (2.25")
- Hole Spacing (center-to-center perpendicular to telescope tube; straight line measurement): 55mm (2.16")
- Hole Spacing (center-to-center perpendicular to telescope tube; measured along curve of base plate): 56mm (2.20")
- Diameter of cutout hole for focuser body: 2.4" (60.9mm)

 

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.