GSO 2" Linear Bearing Crayford Focuser for Refractors - Dual Speed (with 112.5mm Flange)
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New part #: PAF-GS-R112-DW286; Previous part #: PAF-GS-M-LRA-112
1. Selecting the Right Focuser for your Refractor Telescope:
A. Selecting a Focuser Size for your Telescope
This focuser comes with a 112.5mm (4.43") base plate adapter that slides into the rear of your telescope tube. GSO also sells focusers with 86.4mm and 96.6mm diameter bases plates for smaller 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.
B. Selecting a Focuser Model for your Telescope
GSO 2" refractor Crayford focusers (with 112.5mm base plate) are available in 3 versions:
- Dual speed Crayford focuser # GS-M-CRF-112 (sold separately):
Suitable for visual applications with fine focus control or for light imaging payloads. Not compatible with the ZWO EAF out of the box but can be adapted with 3rd party 3d-printed brackets. Finder base (sold separately) can be attached to focuser body. - Dual speed linear bearing focuser # GS-M-LRA-112 (this item):
Suitable for visual applications with fine focus control for heavier eyepieces or for heavier imaging applications. Not compatible with the ZWO EAF out of the box but can be adapted with 3rd party 3d-printed brackets. Shorter tube travel than # 1 above. Finder base cannot be attached to focuser body. - Dual speed ZWO EAF-compatible linear bearing focuser # GS-M-LRA-D-112 (sold separately):
Suitable for visual applications with fine focus control for heavier eyepieces or for heavier imaging applications. Compatible with the ZWO EAF out of the box without the need for other 3rd party brackets. Shorter tube travel than # 1 above. Finder base cannot be attached to focuser body.
2. Description:
This GSO Dual-Speed Linear Focuser for refractor telescopes features the most recent innovation in focuser design to hit the astronomy market in recent years. It is designed specifically to meet the heavier equipment and stability requirements of astrophotography equipment and heavy eyepieces. The linear stability and repeatable quality of focus reached with this focuser will have you returning night after night for more spectacular views, sharper images, and consistent enjoyment!
A. Eliminate Focuser Drawtube Slop
In conventional Crayford focusers, the drawtube is held in place by four roller bearings. Because of the small area of contact between the focuser tube and these bearings, changes in load or telescope orientation can cause some amount of slop in the focuser drawtube. The new linear bearing focuser is built with a cutting-edge rail system made of stainless steel which provides extended, consistent, and linear contact with the focusing mechanism and the inside of the focuser body, even when the focuser is fully extended. The result is zero flexure throughout the focus travel range, even in the worst case scenario when the focuser is parallel to the ground and carrying a heavy load such as a large CCD camera. This linear bearing rail mechanism also allows the use of heavier loads (GSO's rated load capacity for their linear bearing focusers is about 9 lbs (4.1 kgs)).
B. Smooth Focusing Action
The ultra-smooth focuser adjustment knob is only topped by the 10:1 fine adjustment knob which yields superior fine-tuning that will stay in place without slippage for hours on end. You'll feel as if the focuser is gliding on air as you meticulously seek the perfect focus. For critical imaging applications, the focuser position can be locked in place via the large thumbscrew provided for this purpose on the top of the focuser. The focusing tension can be controlled by another large screw on the underside of the focuser. The drawtube features a laser-etched measurement scale for quick and repeatable focusing.
C. Very High Quality Construction and Features
The highly polished, anodized black aluminum is complemented by the meticulous CNC machining. Every part is carefully selected and designed to deliver a linear focusing system that will provide both beauty and quality for years to come. The 2" focuser barrel features a brass compression ring. Also included is a 2"-1.25" adapter with brass compression rings and threads to accept standard 2" filters. The focus travel is 2".
D. 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.
E. 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.
F. 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.
G. Finder Mounting Alert!
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.
Unlike other GSO focuser models and sizes, this 112.5mm Linear Bearing Focuser does NOT have the capability to mount a finder base or bracket directly on the focuser body, so you will have to mount a finder directly elsewhere on your telescope tube.
3. Focuser Specifications:
• Base flange diameter = 4.43" (112.5mm)
• Minimum focuser height (without 1.25" adapter; including flange) = 5.52" (140mm)
• Maximum focuser height (without 1.25" adapter; including flange) = 7.52" (191mm)
• 2"-1.25" adapter height = 0.39" (10mm)
• Flange length (most or all of which inserts into telescope tube) = 0.62" (15.8mm)
• Tube travel = 2" (50.8mm)
• Drawtube outside diameter = 2.32" (59mm)
• Steel rail width = 0.56" (14.1mm)
• Focuser weight (with 1.25" adapter) = 2lb-7.5oz (1119gm)
• Focus knob diameter = 1.57" (40mm)
• Microfocus knob diameter = 1.06" (27mm)
• Maximum outer body diameter = 3.23" (82mm)
• Measurement scale on focuser drawtube: Yes
• Rotatable: Yes
• Dust plug: One 1.25" dust plug included
4. Additional Comments:
• The focuser is shipped in a foam-fitted padded box.
• No instruction manual is included.
| Free Shipping Graphic | Free US Shipping |
|---|---|
| Hide Found a better Shipped Price on Frontend? | No |
New part #: PAF-GS-R112-DW286; Previous part #: PAF-GS-M-LRA-112
1. Selecting the Right Focuser for your Refractor Telescope:
A. Selecting a Focuser Size for your Telescope
This focuser comes with a 112.5mm (4.43") base plate adapter that slides into the rear of your telescope tube. GSO also sells focusers with 86.4mm and 96.6mm diameter bases plates for smaller 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.
B. Selecting a Focuser Model for your Telescope
GSO 2" refractor Crayford focusers (with 112.5mm base plate) are available in 3 versions:
- Dual speed Crayford focuser # GS-M-CRF-112 (sold separately):
Suitable for visual applications with fine focus control or for light imaging payloads. Not compatible with the ZWO EAF out of the box but can be adapted with 3rd party 3d-printed brackets. Finder base (sold separately) can be attached to focuser body. - Dual speed linear bearing focuser # GS-M-LRA-112 (this item):
Suitable for visual applications with fine focus control for heavier eyepieces or for heavier imaging applications. Not compatible with the ZWO EAF out of the box but can be adapted with 3rd party 3d-printed brackets. Shorter tube travel than # 1 above. Finder base cannot be attached to focuser body. - Dual speed ZWO EAF-compatible linear bearing focuser # GS-M-LRA-D-112 (sold separately):
Suitable for visual applications with fine focus control for heavier eyepieces or for heavier imaging applications. Compatible with the ZWO EAF out of the box without the need for other 3rd party brackets. Shorter tube travel than # 1 above. Finder base cannot be attached to focuser body.
2. Description:
This GSO Dual-Speed Linear Focuser for refractor telescopes features the most recent innovation in focuser design to hit the astronomy market in recent years. It is designed specifically to meet the heavier equipment and stability requirements of astrophotography equipment and heavy eyepieces. The linear stability and repeatable quality of focus reached with this focuser will have you returning night after night for more spectacular views, sharper images, and consistent enjoyment!
A. Eliminate Focuser Drawtube Slop
In conventional Crayford focusers, the drawtube is held in place by four roller bearings. Because of the small area of contact between the focuser tube and these bearings, changes in load or telescope orientation can cause some amount of slop in the focuser drawtube. The new linear bearing focuser is built with a cutting-edge rail system made of stainless steel which provides extended, consistent, and linear contact with the focusing mechanism and the inside of the focuser body, even when the focuser is fully extended. The result is zero flexure throughout the focus travel range, even in the worst case scenario when the focuser is parallel to the ground and carrying a heavy load such as a large CCD camera. This linear bearing rail mechanism also allows the use of heavier loads (GSO's rated load capacity for their linear bearing focusers is about 9 lbs (4.1 kgs)).
B. Smooth Focusing Action
The ultra-smooth focuser adjustment knob is only topped by the 10:1 fine adjustment knob which yields superior fine-tuning that will stay in place without slippage for hours on end. You'll feel as if the focuser is gliding on air as you meticulously seek the perfect focus. For critical imaging applications, the focuser position can be locked in place via the large thumbscrew provided for this purpose on the top of the focuser. The focusing tension can be controlled by another large screw on the underside of the focuser. The drawtube features a laser-etched measurement scale for quick and repeatable focusing.
C. Very High Quality Construction and Features
The highly polished, anodized black aluminum is complemented by the meticulous CNC machining. Every part is carefully selected and designed to deliver a linear focusing system that will provide both beauty and quality for years to come. The 2" focuser barrel features a brass compression ring. Also included is a 2"-1.25" adapter with brass compression rings and threads to accept standard 2" filters. The focus travel is 2".
D. 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.
E. 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.
F. 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.
G. Finder Mounting Alert!
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.
Unlike other GSO focuser models and sizes, this 112.5mm Linear Bearing Focuser does NOT have the capability to mount a finder base or bracket directly on the focuser body, so you will have to mount a finder directly elsewhere on your telescope tube.
3. Focuser Specifications:
• Base flange diameter = 4.43" (112.5mm)
• Minimum focuser height (without 1.25" adapter; including flange) = 5.52" (140mm)
• Maximum focuser height (without 1.25" adapter; including flange) = 7.52" (191mm)
• 2"-1.25" adapter height = 0.39" (10mm)
• Flange length (most or all of which inserts into telescope tube) = 0.62" (15.8mm)
• Tube travel = 2" (50.8mm)
• Drawtube outside diameter = 2.32" (59mm)
• Steel rail width = 0.56" (14.1mm)
• Focuser weight (with 1.25" adapter) = 2lb-7.5oz (1119gm)
• Focus knob diameter = 1.57" (40mm)
• Microfocus knob diameter = 1.06" (27mm)
• Maximum outer body diameter = 3.23" (82mm)
• Measurement scale on focuser drawtube: Yes
• Rotatable: Yes
• Dust plug: One 1.25" dust plug included
4. Additional Comments:
• The focuser is shipped in a foam-fitted padded box.
• No instruction manual is included.
| Free Shipping Graphic | Free US Shipping |
|---|---|
| Hide Found a better Shipped Price on Frontend? | No |
GSO 2" Linear Bearing Crayford Focuser for Refractors - Dual Speed (with 112.5mm Flange)