Astromania Telescope Helical Focuser, Double Helical Focuser with 0.05mm Scale and 10mm Focusing Stroke, High Precision Telescope Accessories Focuser 1.25 Inch for Astronomical Telescopes Guidescope

This unit is just what I needed to achieve micro-adjustment focusing when taking pictures through my grab and go telescope, especially at night. The adjustment is very easy and smooth, eliminating a lot of wobble when fine tuning.

The terrible packing job done by Amazon is testament to the mechanical quality of the focuser. It's little box was put inside a long shoebox and it bounced around everywhere, destroying the box and tearing a hole along the outer box seam. I'm amazed it arrived intact. It's a bit tight and will need to be worked over a bit to loosen up, but otherwise it does what it says it does.

For what I payed I'm satisfied with it but if you want top notch quality look elsewhere. Important dimensions: On the scope side the inside diameter is 27mm, some of my longer eyepieces won't fit because of that restriction. Measuring from the eyepiece side down that 27mm restriction is 32mm to 42mm down depending on where you have it focused on its 10mm range. If you plan to attach anything to the 42mm threads on the eyepiece side, everything I attached did not cover the eyepiece holder screws but you might find you need longer screws. The screw for the eyepiece holders is M3.

Perfect addition to my collection. Milky Way season is coming.

I own a fair number of Astromania products and it seems that items with fewer moving parts is generally a safer bet to buy. This item was somewhat pricey relative to their other items and its failure at the two-month mark was highly disappointing. This focuser looks and feels great in hand and feels fairly smooth to operate, but the two focuser tubes are held in sync by a pair of 2mm diameter sliding rods. The mechanism is of a different design that is less robust than the 1.25" focusers that I also own. Obviously a fair amount of time and effort was put into the quality knurling, threading, engravings, and anodizing, and then there's the unexplained use of these thin, weak rods. The focuser happened to be at full extension while I was trying to screw and unscrew my accessories and the rods snapped. They seem to be hardened judging from the clean snap. Both focusing tubes now rotate independently and is useless to me. As an M48-threaded item, people are going to be attaching heavier items off of this focuser. I was using a diagonal and Astromania binoviewer. To lessen the chances of the rods bending or snapping, retract the focuser fully before screwing items onto the threads, and hold the part of the focuser being threaded onto. I found that after the second or third use, there seemed to be much more play in the mechanism compared to new and it struggles with the weight of the diagonal and binoviewer. There are holes drilled inside to accomodate 4 more rods for a total of 6, but I don't think that this is a good design either. The other thing to note is that a 2" barrel will not fit inside this focuser. The male M48 end can be unscrewed to reveal an M56 male thread. For a focuser of this size, slightly enlarging the design to accept a 2" barrel and using M54 threads on both ends would make this a much more versatile focuser, especially when backfocus is limited and using M54 accessories. A larger housing might also allow room for a much more robust internal mechanism. Shortly after my review was posted, the seller reached out to me and offered a full refund and assured me that they forwarded my feedback to their team. This was a welcome relief as this damaged focuser is not useful at all. Increasing from 2 to 3 stars for accepting responsibility, but I don't have a solution as I cannot buy another of the same design.

Very precise and well machined focuser. I use it on my guide scope and it dials in the focus perfectly. Great price too!

Very firm focus. It appears to be an excellent focuser. Works great between my guide camera and OAG.

It starts grinding with a 2 lbs load and when that happens your entire optical train turns as you twist the focuser