GSO 2" 1:10 Linear Bearing Refractor Crayford Focuser with 86.4mm Base Adapter



1. PRODUCT DESCRIPTION

1. Selecting the Right Focuser for your Refractor Telescope:

A. Selecting a Focuser Size for your Telescope

The focuser comes with an 86.4mm (3.40") base plate adapter that slides into the rear of your telescope tube. GSO also sells focusers with 96.6mm and 112.5mm diameter bases plates for larger tubes.

Adapters for the Celestron 80ED and 100ED refractors are also available, but not for any other telescopes.

B. Selecting a Focuser Model for your Telescope

GSO 2" refractor Crayford focusers (with 86.4mm base plate) are available in 4 versions:

  1. Single speed Crayford focuser # GS-CRF-86 (sold separately):
    Suitable for visual applications. Cannot be used with ZWO EAF.
  2. Dual speed Crayford focuser # GS-M-CRF-86 (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.
  3. Dual speed linear bearing focuser # GS-M-LRA-86 (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 and 2 above.
  4. Dual speed ZWO EAF-compatible linear bearing focuser # GS-M-LRA-D-86 (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 and 2 above.


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. 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 M4 threaded screw hole on the upper left side of the body and amother one on the upper right side of the body. Using one of these holes, you can mount any of 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)


3. Focuser 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


4. Additional Comments:

• The focuser is shipped in a foam-fitted padded box.
• No instruction manual is included.

Taiwan

Note: Occasionally, the product you receive might have a slightly different cosmetic appearance or labeling than what is shown. This can often change from batch to batch according to the whims of the manufacturer. However, you will always receive a brand new, original product as described above.

Copyright Notice: This description was developed by Agena AstroProducts. It was NOT provided by the supplier/manufacturer of this product. Please do not copy for personal or commercial use.

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2. ORDERING INFORMATION

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3. US SHIPPING

A. Delivery Time:

  • USPS First Class shipments will generally take 3-5 business days to arrive after we ship it. Priority Mail shipments will generally take 2-3 business days. However, these delivery times are NOT guaranteed by the USPS. Delays of up to 2 (or sometimes even 3) weeks can occur in about 5% of the shipments due to Covid, operational, or other issues.
  • UPS shipments will generally take between 1 and 6 business days to be delivered depending on the method you select.

USPS and UPS do NOT offer any refunds for shipping/delivery delays for ANY reason (except for UPS Next Day Air service). Delays are out of our control once your order ships.

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C. USPS Tracking Limitations: Please note that is common for USPS tracking to show “Shipping Label Created, USPS Awaiting Item” or “Shipment Received, Package Acceptance Pending” even several days after your order ships. This does not mean that there is a problem with your order or that we have not handed over your package to USPS yet. This simply means that your package is en route without an outbound scan and tracking will not be updated until the package reaches a distribution center at your end several days later.

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4. INTERNATIONAL ORDERING / SHIPPING

A. Shipping Cost: Click on the "Shipping and Payments" tab above and select your country to see your shipping choices and cost. If you need a shipping cost estimate for multiple items, please contact us.

B. Delivery Time:

Please note that eBay’s delivery estimates shown are generally too optimistic!

1. UPS (All Shipping Methods):

    • We strongly recommend the use of UPS for international orders due to issues related to the ongoing Covid situation. Delivery time usually varies between 3-7 business days depending on your country and the exact shipping method you select.

2. USPS First Class International:

    • First class packages will usually be carried by GlobalPost (a USPS international delivery partner) for most of the way. Delivery at your end will be handled by your local postal service.
    • Delivery generally takes about 3-4 weeks after we ship your package. This can frequently take 4-6 weeks or more for several countries (8 weeks for Italy, Argentina, and South Africa; 8-12 weeks for Brazil).
    • There is very limited tracking available for 1st class shipments and there is no inquiry/tracing service. Once your package ships, we can do nothing but wait until your package arrives. Please do not become impatient and contact us in 2-3 weeks if your package has not arrived. If you don't receive the package in 6-8 weeks, contact us and we will work with you to resolve the issue.
    • If you don't want to take the risk of this delay or lack of tracking, DO NOT USE First Class mail - use Priority or Express shipping, or better still, UPS instead.
    • Packages are not considered lost unless 60 days have elapsed from the date of shipment.

3. USPS Priority Mail International: Delivery takes about 2 weeks to most countries after we ship your package. This can sometimes take 3-4 weeks to several countries. The USPS provides some basic tracking information for Priority shipping. Packages are not considered lost unless 60 days have elapsed from the date of shipment.

4. USPS Express Mail International: Delivery usually takes 5-10 business days after we ship your package. Packages are not considered lost unless 30 days have elapsed from the date of shipment.

Again, these delivery times are NOT guaranteed by the US Postal Service. The most common reason for delays is slow customs inspection and clearance in your country, and can be very long, even for Express mail packages. Upon shipping your order, delivery delays are beyond our control, so do not leave us negative feedback or file a claim if your package is delayed. Delays are quite common but losses are very rare, so your patience and understanding will be greatly appreciated.

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  • We have no control over these charges and cannot predict what they may be or if they will be levied upon delivery.
  • Customs policies vary widely from country to country (Some countries such as UK are strict about imposing hefty customs duties). It is your responsibility to check with your country's customs office to determine what these additional costs will be prior to buying.
  • Customs fees are normally charged by the delivery company or your country's postal service or collected when you pick the item up. These fees are NOT additional shipping charges.
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5. RETURN/EXCHANGE POLICY

A. US Orders: Returns must be shipped back within 30 days. All returned items must be in brand new, resalable condition with original manufacturer’s packaging. A minimum restocking fee of 10% will be deducted if there is any evidence of use or wear, dirt, scratches, missing packaging/parts, etc. We may levy a larger restocking fee if the condition warrants it, or even refuse returns entirely if returned in heavily used/abused condition. Shipping fees are non-refundable (for items with free or discounted fixed shipping, the actual outbound S&H cost we incurred will be deducted) and you are responsible for all return shipping costs. Please contact us first before returning an item.

B. International Orders: No returns/exchanges accepted unless the item we shipped is defective. Please research the product and ask us any questions BEFORE you purchase to make sure you are buying the correct item for your needs.

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