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

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

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.

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.

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

This focuser has been returned for the reason noted in the Subject, but I would say that if it works in your system, then it appears to be a decent unit. My problem stems from looking for a helical focuser for my OAG, which currently has a rather clunky mechanism for focusing. An important point is that the bottom of the camera (an ASI mini) is about 19 mm from the body of the OAG. Any focuser (and needed adapter from a place like Preci$e Part$) must work with this. On the Astromania, the circular tube comprising the bottom M31 adapter also serves as a seat for whatever guide camera is inserted. That tube is about 18 mm long. With the adapter this would be a bit longer, and all of this was measured at home, inside, etc., so there is great uncertainty that it will work at all with my rig. So I returned it. Another brand (more expensive) apparently does not have this limitation (a rep at a store 100 miles away checked for me). Again, I think the unit itself seems to be very adequate for this job, as long as your needed distance is far enough that you have some leeway either side for focusing. This is certainly why there are both good and bad reviews found here. [On the side, I found the mail packaging and original box to be very poor. It was not protected by a larger box and showed signs of having been under heavy weight. Inside the mailer (heavy paper) the box itself (flimsy cardboard) was partially pushed in, with a thumbscrew being bent--easily straightened out but still... Additionally it was obvious that this was a second (returned before?), since the plastic bag inside the box was damaged and torn, indicating someone else taking it out before. The box itself was missing an end flap too--more evidence. ]

I use this for fine focus on a Newtonian telescope that has a poor focuser. You need to use a Barlow lens (I have a 2x) with this lens.

basic functional but very low quality - go for the more expensive zwo instead. Parts that stand out in poor quality: - the screw nuts are very fragile. They are sharp and unfinished - the ring that is on the telescope side screws out very easily. Therefore you cannot connect a focussed camera with this part in between: a small shift in the screw ring does not only bring your gear out of focus, it may fall apart just as easily.

The worst astro product I've ever purchased. It was damaged. The box it came in was crushed and the unit literally came apart in my hand as I tried to adjust the focus.

Setting up a modified dobsonian, reducing weight etc. This focuser is light and suits my visual observing perfectly.

Intended purpose