Guiding is vital to successful astrophotography. There are plenty of guidescopes available on the market, and the William Optics 50mm Guidescope with 1.25″ ROTO Lock, reviewed here, is good in all regards.
As its name suggests, the William Optics 50mm Guidescope with 1.25″ ROTO Lock has an aperture of 50mm, which in conjunction with its focal ratio of f/4, affords it a good amount of light-gathering ability. This allows it to resolve dim stars, which is useful for modern multi-star guiding algorithms such as those used in PHD2 and the ZWO ASIAIR range series of controllers.
The focal length is 200mm, making it a good choice for main telescopes with mid-range focal lengths. I’ve been using it with my Askar PHQ130 Flatfield Astrograph (review coming soon), which has a focal length of 1000mm. If your imaging telescope is a wide-field rig, say up to 600mm or so, then the William Optics 50mm Guidescope with 1.25″ ROTO Lock may be overkill. You might be better off considering something like the William Optics 32mm Slide-base Uniguide Scope (reviewed here). If your telescope is at the other end of the spectrum and has a very long focal length, then an Off-Axis Guider may give you better results.
Build quality is good, as you’d expect with a William Optics product. It weighs 0.52kg, which gives it some heft but isn’t overly-heavy. Front to back measures 26.5cm. Its white powder-paint finish looks classy, although I noticed a few black patches around the end of the dew shield where the paint hadn’t reached.
So far it’s a fairly standard 50mm guiderscope then, but what sets the William Optics 50mm Guidescope with 1.25″ ROTO Lock apart is that end part of the name: the 1.25″ ROTO Lock. It’s simple to use: twist anti-clockwise to loosen it, then insert your guidecam, and twist clockwise to tighten. It’s like a Baader Clicklock, if you’ve ever come across those. The system does rely on your guidecam having a 1.25″ fit, but this is very common.
The ROTO Lock system fit my ZWO ASI 120MM Mini (review here) perfectly. The guidescope comes with an optional extension tube that screws into the back that’s needed for some cameras to achieve focus. I found that using this allowed me to get a more secure fit.
There are two steps to focussing a guidecam. First, the red collar just behind the dewshield unscrews, allowing the dewshield to be extended; the collar is then tightened to secure it in place. Then the guidecam’s position in the ROTO Lock is adjusted until the view is pin-prick sharp. When focussing my ZWO ASI 120MM Mini I found that I was actually able to skip the first step entirely, leaving the dewshield in its original position.
The guidescope itself is just one part of the system; you also need a way to attach it to your telescope. I used a William Optics Finder Bracket. It’s as well made as the guidescope. Six thumbscrews allow you to align the guidescope to your main telescope, and they have plastic tips to avoid scratching paintwork. A finder bracket is included too.
A version of the William Optics 50mm Guidescope with 1.25″ ROTO Lock is available that has an integrated uniguide slidebase. This is good if your guidescope can fit flush against your main telescope tube, but you lose the fine adjustments afforded by the thumbscrews.
In use, I’ve found the William Optics 50mm Guidescope with 1.25″ ROTO Lock to be very effective. In conjunction with my Sky-Watcher EQ6R-Pro, I routinely manage a guiding RMS in the 0.3″ to 0.6″ range, with my all-time best of 0.29″ being achieved on the second night testing the guidescope. Of course, a guidescope is just one part of an effective guiding system, but the William Optics 50mm Guidescope with 1.25″ RotoLock is a strong component.
Nothing will motivate me to create more content quite like money!
3 thoughts on “Review: William Optics 50mm Guidescope with 1.25″ ROTO Lock”