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ZWO 30 mm f/4 Mini Guide Scope

SKU : ZWO-30120

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  • This 30 mm (1.18-inch) aperture ZWO Guide Scope is compatible with all ASI cameras.
  • Optical Design: Doublet.
  • Aperture: 30 mm (1.18 inches).
  • Focal Ratio: f/4.
  • Focal Length: 120 mm.
  • Camera/Eyepiece Connection: M42x0.75.
  • Back Focus: Adjustable, 0 to 20 mm.

Product Details

  • Once attached to your ASI astro-imaging camera and a computerized mount controller, you will be able to guide your telescope to a desired area of the sky and lock it onto a specific star to hold your images stable.


    The optical lens is made of two simple lenses paired together to bring your images to focus and reduce chromatic aberrations.


    The aperture of this mini-guide scope is only 30 mm (1.18-inches), the focal length is 120 mm, making this a fast focal ratio of f/4. The tube can travel 20 mm, and the back focus is also adjustable from 0 to 20 mm. The overall tube length is 122.5 mm, with the final 3.5 mm being the length from where the camera connection threads begin. The inside diameter of the tube is 30.5 mm. The outside diameter is 44 mm. Your camera connection will be M42*0.75.

    Total weight including the guider ring and dovetail: 250 g (0.55 pounds).

  • specifications

    Aperture30 mm (1.18")
    Back Focus0 to 20mm
    Camera/Eyepiece ConnectionM42x0.75
    Dawes Limit3.87 arcseconds
    Focal Length120 mm
    Focal Ratiof/4
    Free ShippingYes
    Hightest Magnification60x
    Light Gathering Power18x
    Tube Length122.5mm
    Weight0.55 lb (250 g)
  • included items

    • 30 mm mini guide scope.
    • Dovetail with mounting ring (one-fourth-inch screw hole).

Product Reviews

Customer Reviews
4.3 Based on 10 Reviews
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Dave M.
United States United States
Effective and easy

Purchased this scope to use as a guidescope when imaging with my camera with a lens rather than a telescope. Paired this scope with an ASI120mm-s CMOS camera and attached it to a universal L bracket. the camera and guidescope work well together using PHD II guiding software. Once the initial focus is set the scope needs no further adjustments. The scope/camera combo is light and portable adding very little weight to my main camera and lens set up. This makes the whole rig easy to balance and the tracking is very accurate.

Joel S.
United States United States
Best place to buy from

Every time I order from OPT my order arrives in a timely manner and they keep me informed of the entire process. This little scope packs a powerful punch in guiding your mount and is a quality piece of equipment to add to your arsenal. Can't go wrong with this scope.

United States United States
Woble when mounted on hot shoe of camera, not stable.

Cheap piece of equipment, with only one adjustable screw to lock it in the hot shoe of any camera is a laugh, too much play. The mount should be of Arca Swiss Fitting so it will fit in the newer style plates and not to have to piggy back an L plate and an additional quick release plate by Neewer Casey D

Frank R.
United States United States

Admittedly, this is my first guide scope, but I’ve never had any difficulty focusing a cheap finder scope. This one drives me nuts. Hard to find focus in the first place—if you’re using an ASI290 mini you’ll need to screw on the extension tube—and then tightening the keeper ring knocks it out of focus again. Hard to get an HFM below 4. Yeah, it’s light but. . . . There’s no way to adjust the aim of it, either. Some people say it’s not important to align a guidescope with the main but I want it in the ballpark. I jammed a washer into the bracket to jimmy it into place. It fogs up like any other lens, so you’ll need a heater on it. With the 290 in place it’s doing an OK job with my 101mm refractor, though I don’t know how much better my guiding would be with a different scope; this is my first. Now that I have it I’ll keep it, but for my next scope I’ll look for something different.

Kinchen S.
United States United States
Very Handy

I got this to fit in the shoe on the original model WO White Cat. It works very well and is a nice set up.

John M.
United States United States
came in one shipment

This shipment was fine but my next purchase I am still waiting for items that were on back order, it has been three weeks.