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GSO 2" Linear Bearing Crayford Focuser for Refractors - Dual Speed (with 86.4mm Flange)
| Brand | GSO |
| Part Number | PAF-GS-LBR86 |
| Availability | available |
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Product Info
Manufacturer 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!
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)).
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.
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".
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.
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.
Selecting a Focuser Model for your Telescope
The focuser comes with an 86.4mm (3.40") base plate adapter.
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.
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.
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 screw on the upper left side of the body and one finder mounting screw on the upper right side of the body. Using one of these holes, you can mount the following finder bases/brackets, all of which are sold separately:
1) Agena modified Synta/Vixen style dovetail base for Crayford focusers # CFURB using one screw (on left or right side)
2) Agena Synta/Vixen style deluxe cross-slot dovetail base # XFURB using one screw (on left or right side)
3) GSO 50mm finder bracket with base # 8KB01 using one screw (on left or right side)
Specifications:
• Base flange diameter = 3.40" (86.4mm)
• Minimum focuser height (without 1.25" adapter; including flange) = 4.21" (107mm)
• Maximum focuser height (without 1.25" adapter; including flange) = 6.21" (158mm)
• 2"-1.25" adapter height = 0.39" (10mm)
• Flange length (most or all of which inserts into telescope tube) = 0.59" (15mm)
• Tube travel = 2" (50.8mm)
• Drawtube outside diameter = 2.32" (59mm)
• Steel rail width = 0.56" (14.1mm)
• Focuser weight (with 1.25" adapter) = 1lb-14.5oz (864gm)
• 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, but see description above
• Dust plug: One 1.25" dust plug included
Additional Comments
• The focuser is shipped in a foam-fitted padded box.
• No instruction manual is included.
Reviews
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May 8, 2019
Nice engineered piece of gear but
Pros: Cons: Comments:But it could come with a couple of spare M4 screw sets to attach focuser to OTA
Bottom Line: Would you recommend this item? Yes
I wouldn’t mind paying an extra couple of bucks on it instead of using HomeDepot screws...This review was provided courtesy of AgenaAstro.com
Nov 16, 2018GSO linear bearing focuser - Perfect!
Pros: Cons: Comments:This is probably one of the best focuser's you can upgrade to for what it is. Totally smooth draw, zero back lash. Amazing micrometer control. Why go with a feather-touch focuser that costs 2.5 times more when this thing is equally comparable?
Bottom Line: Would you recommend this item? Yes
The 86mm flange was a perfect fit, even on my 50 year old refractor. The flanges are built to accomidate multiple telescope diameters and are simple to switch out with out special tools.
The GSO linear bearing drive system is a world of greatness. There is zero slop in the squareness, fully extended when I have an excessive amount of gear inserted into the focuser. It is dead center to the objective and no amount of pressing on the draw tube moves it.
This is the perfect focuser for modified solar telescopes, period. When you have a 2lb hydrogen alpha filter installed that is sensitive to misalignment, the GSO linear bearing focuser will not be the culprit of misalignment. It is precision milled to very tight standards.
I have zero complaints! This focuser is one of the best and you arent stuck with a cost premium because some trademarked word stamped on its side.This review was provided courtesy of AgenaAstro.com
Aug 1, 2018Upgrade to a Celestron C80
Pros: Cons: Comments:The C80 originally came with a rack and pinion type focuser, which is sufficient for daylight spotting. Upgrading to a GSO has immensely improved the visual and photographic performance. The C80 lens, and ED doublet, is tack sharp and this focuser allows it to work to its full potential.
Bottom Line: Would you recommend this item? YesThis review was provided courtesy of AgenaAstro.com
Jan 24, 2018GSO Linear focuser
Pros: Cons: Comments:This was a replacement for my old GSO Crayford on my Burgess 91MM refractor. Installation was a breeze even though I had to modify the mating flange a bit.
Bottom Line: Would you recommend this item? Yes
Works very well.This review was provided courtesy of AgenaAstro.com
Avani Soares Well-Known Member
- Skill Level
- Unknown
- Time with Product
- Unknown
- User Notes:
- Review by Soares A.
Oct 24, 2017My thoughts on this product
Pros: Cons: Comments:It does not have as smooth a feel as I thought it would. when you set the tension screw it works very well in spots, but then hits spots that make it feel like it is grinding on the bearing.
Bottom Line: Would you recommend this item? Yes
I don't believe the bearing is ground to a smooth flat surface from one end to the other. It seems like it has high and low spots. When you loosen the screw to prevent the grinding and the hit a low spot the focuser will slip out all the way to the stop. They need to pay more attention to the flat side where the tension screw is all that is holding it in focus. Maybe I just got one made on a Friday and there not all like this.
I probably should have sent it back for an exchange, but I thought it might smooth out, and it has not.This review was provided courtesy of AgenaAstro.com
Oct 14, 2017Good upgrade to Barska Magnus 80ed with 90 x 1mm adapter
Pros: Cons: Comments:Bought this to upgrade the focuser on my Barska Magnus 80ed. This attaches to the optical tube with a 90mm x 1mm threading adapter. I followed the information for this found on this thread:
Bottom Line: Would you recommend this item? Yes
https://www.cloudynights.com/topic/253608-cheapest-ed-apo-yet-barska-magnus/
The original focuser is difficult to remove - there are 4 screws arranged in a rectangular pattern for openings to attach a dovetail (I believe) that need to be removed. then I used a strap wrench to turn it off. The adapter screwed in easily, and this focuser slipped without effort into the adapter, then tightened in with the retaining screws taken out of the original focuser. In all, about a 5min. upgrade
While not a feathertouch, this focuser is a significant (worth it) upgrade to the original. Having the 360 degree rotational capability is a big plus for framing astrographs while remaining in focus.
Just wanted to add this information, because I was looking for this in the reviews before I purchased it. I hear it works the same for Orion 80ed scopes.This review was provided courtesy of AgenaAstro.com
Sep 1, 2017GSO Focuser - nicely done!
Pros: Cons: Comments:The fit and finish of the GSO two stage focuser is excellent. The function is very good too. The only problem that I've had with it is when my scope is oriented vertically with a heavy load to lift during focusing. Mine was an extreme case because the focuser had to lift a Quark and a cooled camera including extension tubes. It held the load just fine, but precision focusing was not possible w/o helping to lift the load into position by hand and locking it securely when focus was achieved.
Bottom Line: Would you recommend this item? YesThis review was provided courtesy of AgenaAstro.com
Apr 18, 2017GSO 2" Linear Bearing Crayford Focuser for Refractors - Dual Spee
Pros: Cons: Comments:I bought this to replace the stock rack and pinion focuser on my Orion ShortTube 80 refractor. The quality and performance of this focuser is excellent. My only issue with it is the short focus travel that requires the use of an extension tube to reach focus.
Bottom Line: Would you recommend this item? YesThis review was provided courtesy of AgenaAstro.com
Apr 10, 2017good replacement for standard focusers
Pros: Cons: Comments:I have a few of these now and they are a good replacement for the basic single speed focuser. I have not had issues with image shift that I had with the original focuser on scope.
Bottom Line: Would you recommend this item? YesThis review was provided courtesy of AgenaAstro.com
Jan 10, 2017Quality replacement focuser
Pros: Cons: Comments:This focuser is very well made, great addition to C80ED, with Agena adaptor. I did have to purchase 2" extension to reach focus with all eyepieces and DSLR.
Bottom Line: Would you recommend this item? YesThis review was provided courtesy of AgenaAstro.com
Lord Beowulf New Member
- Skill Level
- Unknown
- Time with Product
- Unknown
- User Notes:
- Review by Lord Beowulf of Cedar Park, TX.
Feb 25, 2012Great focuser, especially for the price
Pros:Strong Construction
Cons: Comments:Overall this is a really nice Crayford focuser, especially for the price. The only drawback for the application of a large refractor is that the draw tube is too short to reach focus on most eyepieces. Thus you have to add extensions for some eyepieces, making the result rather ungainly. Unfortunately, for other eyepieces the extension is too much, so there's a lot of fiddling to find the right combinations of extension or no extension.
Bottom Line: Would you recommend this item? YesThis review was provided courtesy of AgenaAstro.com
Oct 28, 2011A Very Good Focuser
Pros:Easy to Use,Strong Construction,Accurate
Cons: Comments:I have both the standard GSO Crayford and now the Linear Track version of the same. The LT is a better product...there are no Crayford ball bearings to mar the top of the focus tube. The mechanical construction is typical GSO and the focus motion is very smooth like the standard model. BTW: Agena gives excellent support to his customers!
Bottom Line: Would you recommend this item? YesThis review was provided courtesy of AgenaAstro.com
Sort bySpecifications
Manufacturer GSO Focuser Telescope Type Refractor
