Please note: GSO has modified this model slightly, and the latest version of this item cannot accept dovetail bases for finders as previous versions or some other sizes can. The overall body length of this new version is also a bit (8mm) shorter than before. Also, the rotation collar may be silver (as shown in the photos) or black depending on stock.
This very high quality, dual-speed Crayford focuser for refractor telescopes from Guan Sheng Optical (GSO) is beautifully machined and a joy to use. You will wonder how you ever lived without it once you install it!
1. Smooth Focusing Action
The Crayford style focusing control makes achieving precise focus for visual observations and astrophotography a breeze and you will experience very smooth and precisely controlled focuser motion with zero backlash and zero image shift.
2. High-Quality Construction and Features
CNC machined from aluminum and anodized black, this focuser comes with a base plate adapter to attach to refractor telescopes. The inner drawtube glides on 4 precision bearings and a roller shaft and provides 79mm (3.11") 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 inner draw-tube barrel is anodized black and features a laser-etched scale.
3. Tension Adjustment and Focus-Lock
The focuser has two large thumbscrews on the underside. 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 about 6 lbs (2.7 kgs).
4. 360-degree Rotation
This focuser model features a large black (not silver as shown above) rotation collar which makes it a breeze to rotate the focuser in the desired orientation for maximum comfort. Note that the silver rotation thumbscrew in the photo above is not applicable to this focuser and is often not included.
5. Focuser Installation
The focuser is easily attached to a telescope tube with three M4 screws (not included) spaced 120 degrees apart on the flange. Installation is usually a 5 minute job that involves removing your old focuser, sliding in the new Crayford focuser, and screwing it on to the telescope tube. In almost all cases, the original screws used on your OEM focuser will also work for this Crayford focuser. If not, you will have to buy the M4 screws from a local hardware store. You will just need a Philips (cross-slot) screw-driver to perform this upgrade.
We strongly recommend that you make sure that you can remove your old focuser from your telescope tube before buying this item. Some OEM R&P focusers can be very hard to remove.
6. Selecting a Focuser Model for your Telescope
The focuser comes with a 112.5mm (4.43”) base plate adapter.
If this focuser flange size (112.5mm) does not fit your telescope, we also sell some other adapters that can be used to connect this focuser to several telescope models from Antares, Meade, Celestron, and others. Adapters for the popular Celestron 80ED and 100ED refractors are also available.
7. Focus Travel Issues
Most Crayford focuser units are shorter than existing R&P focusers. So while you will typically have more in-focus travel with a new Crayford focuser (which is great for imaging applications), you might not have sufficient out-focus travel to reach focus with all your eyepieces/accessories. In such cases, the problem can be easily fixed with 2" extension tubes that are available separately.
8. Optional Finder Mounting Options
In many existing focusers, the base for your finder bracket is molded onto the focuser body. When you replace the existing focuser with a Crayford focuser, you will lose this base to mount your finder.
This new version of the GSO focuser has three finder mounting screws on the upper left side of the body and one finder mounting screw on the upper right side of the body. Unfortunately, you can no longer attach conventional Synta-style dovetail bases as in previous versions. However, using one of these holes, you can mount the following finder bases/bracket which is sold separately:
- GSO 50mm finder bracket with base # 8KB01 using one screw (on left or right side)
9. Focuser Specifications
• Flange outer diameter on telescope adapter: 112.5mm (4.43”)
• Minimum focuser height (with 1.25" adapter and base flange) = 147mm (5.79”)
• Maximum focuser height (with 1.25" adapter and base flange) = 226mm (8.90”)
• Minimum focuser height (without 1.25" adapter but with base flange) = 137mm (5.39”)
• Maximum focuser height (without 1.25" adapter but with base flange) = 216mm (8.50”)
• Tube travel = 79mm (3.11")
• Focuser weight (with 1.25" adapter) = 2lb-10.2oz (1196gm)
• Focus knob diameter = 40mm (1.57")
• Microfocus knob diameter = 26mm (1.02”)
• Laser-etched scale markings on focuser drawtube: Yes
• Rotatable: Yes (using silver/black collar)
• 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.