This GSO Dual-Speed Linear Focuser for RC 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".
These focusers are rotatable, i.e., you can turn the entire focuser body/diagonal/eyepiece combination into a better observing position by loosening the silver collar, turning the focuser body, and locking the silver collar again into place.
Telescope Compatibility and Focuser Installation
The telescope end of this focuser has a silver ring with an M90x1 female thread. Thus, it can be easily screwed on to 6" or 8" Ritchey-Chretien telescopes manufactured by GSO that feature this male thread on the rear end. These telescopes are sold all over the world under various brand names (Astro-Tech, GSO, Altair Astro, etc.).
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.
• Base flange knurled outer diameter = 3.78" (96mm)
• Base flange thread = M90x1 female (90mm nominal diameter; 1mm thread pitch)
• Minimum focuser height (without 1.25" adapter; including flange) = 4.21" (107mm)
• Maximum focuser height (without 1.25" adapter; including flange) = 3.5" (89mm)
• 2"-1.25" adapter height = 0.39" (10mm)
• 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-9.6oz (726gm)
• 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.