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".
This focuser model features a large black (not silver as shown in the photos above) rotation collar which makes it a breeze to rotate the focuser in the desired orientation for maximum comfort.
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 112.5mm (4.43") base plate adapter.
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.
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 on your telescope tube.
• 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
• The focuser is shipped in a foam-fitted padded box.
• No instruction manual is included.
Jan 1, 2018
Great focuserPros: Cons: Comments:
Perfect fit for my Celestron OMNI 120 XLT. Construction and operation are worth five stars. I gave it four star as two issues make it a little bit cumbersome or require extra work or thinking: (1) Does not have a holder for a finder and (2) the out focus travel is so much shorter compared to the original R&P focuser that I ended up needing two (!) extension tubes (for planets, I use a binoviewer with a barlow far away from the eyepieces which extends the focal length quite a bit.) However, the in focus travel is better than R&P and I suspect that I will be able to use the binoviewer even without a barlow (Not possible with R&P). If this turns out to be true, it will be a great thing. I have yet to test it, though.
This review was provided courtesy of AgenaAstro.comDec 24, 2016
Good value, built solidPros: Cons: Comments:
I bought this to use on an F15, 6" refractor that I am building. In the mean time I installed it on a Celestron 120 mm refractor. It works great, looks like it will hold a lot of weight without slipping and has a very nice rotating feature.
This review was provided courtesy of AgenaAstro.com
Dan Acker Member
- Skill Level
- Time with Product
Sep 27, 2013
- User Notes:
- Review by Dan of Harleysville, PA.
Best Focuser on the Market!Pros:
Strong Construction,Easy to UseCons: Comments:
Attaching the GSO Linear Focuser to my Orion 120mm f/8.3 1000mm refractor was easy but the flange made a tight fit. A little tapping was required. This is a solid, well built focuser with very stable and accurate movement. An absolute joy to use.
This review was provided courtesy of AgenaAstro.comMay 30, 2013
Strong Construction,AccurateCons: Comments:
I had to remove 30 thousands of an inch to get it to fit my 80's celestron spc 102 but that was easy and the fit was then perfect, quality and presicion are superb. I can't believe the difference from the original rack and pinion focuser, great!
This review was provided courtesy of AgenaAstro.comMar 1, 2013
Smooth,Very Precise,Strong Construction,No Sag In Drawtube,Easy to Use,Smooth RotationCons: Comments:
I installed this focuser on a Skywatcher 120ED refractor. I knew that the flange diameter would be approximately 1mm too large but I ground off the necessary material and the flange now fits the tube perfectly. The standard GSO 2 speed is very nice but this is somewhat better. I regularly use heavy binoviewers and this focuser handles them with ease.
This review was provided courtesy of AgenaAstro.comSort by
Manufacturer GSO Focuser Telescope Type Refractor