GSO 2" EAF Compatible Linear Bearing Crayford Focuser for SCTs - Dual Speed
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Current part #: PAF-GS-SCT-DW324; Previous part #s: PAF-GS-M-LST-D or PAF-GS-M-LR-D-SCT
1. Selecting the Right Focuser for your SCT Telescope:
GSO 2" SCT Crayford focusers are available in 4 versions:
- Single speed Crayford focuser # GS-CRF-SCT (sold separately):
Suitable for visual applications. Cannot be used with ZWO EAF. Shorter length so suitable for use with telescopes on fork, alt-az or EQ mounts. - Dual speed Crayford focuser # GS-M-CRF-SCT (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. Shorter length so suitable for use with telescopes on fork, alt-az or EQ mounts. - Dual speed linear bearing focuser # GS-M-LST (sold separately):
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. Longer body length so suitable for use with telescopes on alt-az or EQ mounts only (not usable with fork mounts). - Dual speed ZWO EAF-compatible linear bearing focuser # GS-M-LST-D (this item):
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. Longer body length so suitable for use with telescopes on alt-az or EQ mounts only (not usable with fork mounts).
2. Description:
This GSO Dual-Speed Linear Focuser for SCT 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 SCT Image Shift
Many users find the primary mirror focusing mechanism of Schmidt-Cassegrain telescopes (SCT) cumbersome to use. There is some amount of image shift and precise focus cannot be found easily. This is inconvenient for visual use and a serious problem for astrophotography. By relying on this focuser for fine focusing instead of the telescope's movable primary mirror, image shift is completely eliminated, and you will experience very smooth and precisely controlled focuser motion.
B. 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)).
C. 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.
D. Out of the Box Compatibility with the ZWO EAF Electronic Automatic Focuser
All other versions of GSO's SCT 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
E. Rotatable for Maximum Comfort
This deluxe model features a 360-degree rotatable ring that allows you to orient the focuser (and hence your diagonal/eyepiece/camera) to the most comfortable viewing or imaging position.
F. 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 and can accept standard 2" refractor-type diagonals and other 2" accessories (Note that the use of this focuser converts your telescope's rear SCT thread to a 2" visual back. As a result you will not be able to use an SCT-type diagonal with this focuser; you will need a refractor-type diagonal instead). Also included is a 2"-1.25" adapter with brass compression rings and threads to accept standard 2" filters.
G. Easy Installation and Use
Installation is a simple matter of threading the focuser’s flange onto the standard male SCT thread (which is a 2" x 24 TPI thread) on the rear of your SCT telescope. Please note that some Celestron telescopes made in the late 1970s and early 1980s did not have a standard thread pitch. This focuser will not fit those, and there is no way for us to know what threads you might have on your telescope.
To focus, simply use your main SCT focusing knob to bring your scope into the ballpark range of focus, then fine tune with the focusing knobs built into your linear focuser. It’s that simple! With a generous 2" focus travel range, you may never need to touch your SCT's main focuser knob again!
3. Specifications:
• Minimum focuser height (without 1.25" adapter) = 4.66" (118.5mm)
• Maximum focuser height (without 1.25" adapter) = 6.63" (168.5mm)
• 2"-1.25" adapter height = 0.39" (10mm)
• Tube travel = 1.97" (50mm)
• Drawtube outside diameter = 2.32" (59mm)
• Steel rail width = 0.56" (14.1mm)
• Focuser weight (with 1.25" adapter) = 2lb-2oz (966gm)
• Focus knob diameter = 1.57" (40mm)
• Microfocus knob diameter = 1.06" (27mm)
• Maximum outer body diameter = 3.23" (82mm)
• Flange thread: Standard SCT female thread (2" x 24 TPI)
• 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.
| Product Banner Type | new |
|---|---|
| Free Shipping Graphic | Free US Shipping |
| Hide Found a better Shipped Price on Frontend? | No |
Current part #: PAF-GS-SCT-DW324; Previous part #s: PAF-GS-M-LST-D or PAF-GS-M-LR-D-SCT
1. Selecting the Right Focuser for your SCT Telescope:
GSO 2" SCT Crayford focusers are available in 4 versions:
- Single speed Crayford focuser # GS-CRF-SCT (sold separately):
Suitable for visual applications. Cannot be used with ZWO EAF. Shorter length so suitable for use with telescopes on fork, alt-az or EQ mounts. - Dual speed Crayford focuser # GS-M-CRF-SCT (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. Shorter length so suitable for use with telescopes on fork, alt-az or EQ mounts. - Dual speed linear bearing focuser # GS-M-LST (sold separately):
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. Longer body length so suitable for use with telescopes on alt-az or EQ mounts only (not usable with fork mounts). - Dual speed ZWO EAF-compatible linear bearing focuser # GS-M-LST-D (this item):
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. Longer body length so suitable for use with telescopes on alt-az or EQ mounts only (not usable with fork mounts).
2. Description:
This GSO Dual-Speed Linear Focuser for SCT 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 SCT Image Shift
Many users find the primary mirror focusing mechanism of Schmidt-Cassegrain telescopes (SCT) cumbersome to use. There is some amount of image shift and precise focus cannot be found easily. This is inconvenient for visual use and a serious problem for astrophotography. By relying on this focuser for fine focusing instead of the telescope's movable primary mirror, image shift is completely eliminated, and you will experience very smooth and precisely controlled focuser motion.
B. 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)).
C. 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.
D. Out of the Box Compatibility with the ZWO EAF Electronic Automatic Focuser
All other versions of GSO's SCT 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
E. Rotatable for Maximum Comfort
This deluxe model features a 360-degree rotatable ring that allows you to orient the focuser (and hence your diagonal/eyepiece/camera) to the most comfortable viewing or imaging position.
F. 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 and can accept standard 2" refractor-type diagonals and other 2" accessories (Note that the use of this focuser converts your telescope's rear SCT thread to a 2" visual back. As a result you will not be able to use an SCT-type diagonal with this focuser; you will need a refractor-type diagonal instead). Also included is a 2"-1.25" adapter with brass compression rings and threads to accept standard 2" filters.
G. Easy Installation and Use
Installation is a simple matter of threading the focuser’s flange onto the standard male SCT thread (which is a 2" x 24 TPI thread) on the rear of your SCT telescope. Please note that some Celestron telescopes made in the late 1970s and early 1980s did not have a standard thread pitch. This focuser will not fit those, and there is no way for us to know what threads you might have on your telescope.
To focus, simply use your main SCT focusing knob to bring your scope into the ballpark range of focus, then fine tune with the focusing knobs built into your linear focuser. It’s that simple! With a generous 2" focus travel range, you may never need to touch your SCT's main focuser knob again!
3. Specifications:
• Minimum focuser height (without 1.25" adapter) = 4.66" (118.5mm)
• Maximum focuser height (without 1.25" adapter) = 6.63" (168.5mm)
• 2"-1.25" adapter height = 0.39" (10mm)
• Tube travel = 1.97" (50mm)
• Drawtube outside diameter = 2.32" (59mm)
• Steel rail width = 0.56" (14.1mm)
• Focuser weight (with 1.25" adapter) = 2lb-2oz (966gm)
• Focus knob diameter = 1.57" (40mm)
• Microfocus knob diameter = 1.06" (27mm)
• Maximum outer body diameter = 3.23" (82mm)
• Flange thread: Standard SCT female thread (2" x 24 TPI)
• 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.
| Product Banner Type | new |
|---|---|
| Free Shipping Graphic | Free US Shipping |
| Hide Found a better Shipped Price on Frontend? | No |
GSO 2" EAF Compatible Linear Bearing Crayford Focuser for SCTs - Dual Speed