GSO 2" EAF Compatible Crayford Focuser for Refractors - Dual Speed (with 86.4mm Telesco...
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1. Selecting the Right Focuser for your Refractor Telescope:
A. Selecting a Focuser Size for your Telescope
The focuser comes with an 86.4mm (3.40") base plate adapter that slides into the rear of your telescope tube. GSO also sells focusers with 96.6mm and 112.5mm diameter bases plates for larger tubes.
- Click here for a telescope compatibility table to see which focuser might work for you.
- Click here to see photos of Crayford focuser installations on various telescopes.
Adapters for the Celestron 80ED and 100ED refractors are also available, but not for any other telescopes.
B. Selecting a Focuser Model for your Telescope
2. Description:
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!
A. 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.
B. 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.
C. Out of the Box Compatibility with the ZWO EAF Electronic Automatic Focuser
All other versions of GSO's refractor focusers have a rounded or curved housing over the focusing mechanism, making it either impossible or hard to attach ZWO's EAF for automatic focusing control. After our prodding for almost 2 years, GSO redesigned the housing with a flat surface and with additional screw holes to allow users to easily and directly mount the ZWO EAF using the standard mounting bracket that the EAF comes with. The housing in this version is also made of aluminum for a secure, robust fit. Imagers can now use the EAF to precisely control the focuser's movement for visual or critical imaging applications. Note that the EAF is not included
D. 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).
E. 360-degree Rotation
These focusers are rotatable, i.e., you can turn the entire focuser body/diagonal/eyepiece combination into a better observing position by loosening or tightening a large silver thumbscrew on the top of the focuser. However, please note that this is a relatively weak feature of this otherwise excellent product. We inspect every single focuser and tweak/lube it as much as we can, but the rotation is often not smooth over the entire 360-degrees and may bind in a few spots, requiring additional effort to rotate it. This is probably a minor annoyance since most people will not use this feature very often.
F. 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.
G. Focus Travel Issues
Most Crayford focusers are shorter than existing R&P focusers on refractors. So while you will typically have more in-focus travel with a new Crayford focuser (which is great for imaging or binoviewing applications), you might not have sufficient out-focus travel to reach focus with all your eyepieces/accessories.
If you run out of outward focus travel with the new focuser, the problem can be easily fixed with 2" extension tubes that are available in separately in several different lengths (35mm, 50mm or 80mm are the most common). Note, however, that the exact length of extension required depends on your specific collection of diagonals, eyepieces, barlows, etc. and will be different for everyone. Hence, we cannot tell you what length of extension you might need. To determine this, please compare the minimum and maximum length of your original focuser with the detailed specifications of this focuser provided below to determine what your shortfall, and hence the length of the extension required, might be.
H. 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 version of the GSO focuser has one finder mounting M4 threaded screw hole on the upper left side of the body and amother one on the upper right side of the body. Using one of these holes, you can mount any of the following finder bases/brackets, all of which are sold separately:
- Agena modified Synta/Vixen style dovetail base for Crayford focusers # CFURB using one screw (on left or right side)
- Agena Synta/Vixen style deluxe cross-slot dovetail base # XFURB using one screw (on left or right side)
- GSO 50mm finder bracket with base # 8KB01 using one screw (on left or right side)
3. Focuser Specifications
• Flange outer diameter on telescope adapter: 86.4mm (3.40")
• Minimum focuser height (with 1.25" adapter and base flange) = 104.1mm (4.1")
• Maximum focuser height (with 1.25" adapter and base flange) = 170.6mm (6.72")
• Minimum focuser height (without 1.25" adapter but with base flange) = 94mm (3.70")
• Maximum focuser height (without 1.25" adapter but with base flange) = 162.5mm (6.4")
• Tube travel = 69.8mm (2.74")
• Focuser weight (with 1.25" adapter) = 2lb-1.7oz (955g)
• Focus knob diameter = 40mm (1.57")
• Microfocus knob diameter = 26mm (1.02”)
• Laser-etched scale markings on focuser drawtube: Yes
• Rotatable: Yes (but see description above)
• Dust plug: One 1.25" dust plug included
4. Additional Comments:
• 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.
• The focuser is shipped in a foam-fitted padded box.
• No instruction manual is included.
| Product Banner Type | new |
|---|---|
| Free Shipping Graphic | Free US Shipping |
| Hide Found a better Shipped Price on Frontend? | No |
1. Selecting the Right Focuser for your Refractor Telescope:
A. Selecting a Focuser Size for your Telescope
The focuser comes with an 86.4mm (3.40") base plate adapter that slides into the rear of your telescope tube. GSO also sells focusers with 96.6mm and 112.5mm diameter bases plates for larger tubes.
- Click here for a telescope compatibility table to see which focuser might work for you.
- Click here to see photos of Crayford focuser installations on various telescopes.
Adapters for the Celestron 80ED and 100ED refractors are also available, but not for any other telescopes.
B. Selecting a Focuser Model for your Telescope
2. Description:
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!
A. 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.
B. 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.
C. Out of the Box Compatibility with the ZWO EAF Electronic Automatic Focuser
All other versions of GSO's refractor focusers have a rounded or curved housing over the focusing mechanism, making it either impossible or hard to attach ZWO's EAF for automatic focusing control. After our prodding for almost 2 years, GSO redesigned the housing with a flat surface and with additional screw holes to allow users to easily and directly mount the ZWO EAF using the standard mounting bracket that the EAF comes with. The housing in this version is also made of aluminum for a secure, robust fit. Imagers can now use the EAF to precisely control the focuser's movement for visual or critical imaging applications. Note that the EAF is not included
D. 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).
E. 360-degree Rotation
These focusers are rotatable, i.e., you can turn the entire focuser body/diagonal/eyepiece combination into a better observing position by loosening or tightening a large silver thumbscrew on the top of the focuser. However, please note that this is a relatively weak feature of this otherwise excellent product. We inspect every single focuser and tweak/lube it as much as we can, but the rotation is often not smooth over the entire 360-degrees and may bind in a few spots, requiring additional effort to rotate it. This is probably a minor annoyance since most people will not use this feature very often.
F. 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.
G. Focus Travel Issues
Most Crayford focusers are shorter than existing R&P focusers on refractors. So while you will typically have more in-focus travel with a new Crayford focuser (which is great for imaging or binoviewing applications), you might not have sufficient out-focus travel to reach focus with all your eyepieces/accessories.
If you run out of outward focus travel with the new focuser, the problem can be easily fixed with 2" extension tubes that are available in separately in several different lengths (35mm, 50mm or 80mm are the most common). Note, however, that the exact length of extension required depends on your specific collection of diagonals, eyepieces, barlows, etc. and will be different for everyone. Hence, we cannot tell you what length of extension you might need. To determine this, please compare the minimum and maximum length of your original focuser with the detailed specifications of this focuser provided below to determine what your shortfall, and hence the length of the extension required, might be.
H. 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 version of the GSO focuser has one finder mounting M4 threaded screw hole on the upper left side of the body and amother one on the upper right side of the body. Using one of these holes, you can mount any of the following finder bases/brackets, all of which are sold separately:
- Agena modified Synta/Vixen style dovetail base for Crayford focusers # CFURB using one screw (on left or right side)
- Agena Synta/Vixen style deluxe cross-slot dovetail base # XFURB using one screw (on left or right side)
- GSO 50mm finder bracket with base # 8KB01 using one screw (on left or right side)
3. Focuser Specifications
• Flange outer diameter on telescope adapter: 86.4mm (3.40")
• Minimum focuser height (with 1.25" adapter and base flange) = 104.1mm (4.1")
• Maximum focuser height (with 1.25" adapter and base flange) = 170.6mm (6.72")
• Minimum focuser height (without 1.25" adapter but with base flange) = 94mm (3.70")
• Maximum focuser height (without 1.25" adapter but with base flange) = 162.5mm (6.4")
• Tube travel = 69.8mm (2.74")
• Focuser weight (with 1.25" adapter) = 2lb-1.7oz (955g)
• Focus knob diameter = 40mm (1.57")
• Microfocus knob diameter = 26mm (1.02”)
• Laser-etched scale markings on focuser drawtube: Yes
• Rotatable: Yes (but see description above)
• Dust plug: One 1.25" dust plug included
4. Additional Comments:
• 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.
• The focuser is shipped in a foam-fitted padded box.
• No instruction manual is included.
| Product Banner Type | new |
|---|---|
| Free Shipping Graphic | Free US Shipping |
| Hide Found a better Shipped Price on Frontend? | No |
GSO 2" EAF Compatible Crayford Focuser for Refractors - Dual Speed (with 86.4mm Telescope Adapter)