[mental4astro (Alexander)]

P & C,

I have a couple of those cheap 0.5X reducers. One is a GSO, and the other a Svbony (really cheap). The GSO one works really well. The Svbony is a shocker, same scope and camera, with terrible flaring as you described. The two reducers are of slightly different design and appearance.

Your experience and what you did in reversing the position of the elements have given me an idea to do the same with this Svbony item - nothing to lose by doing so.

Yes, it is often the case an issue with QC with many Chinese made products. It only takes on element to be carelessly reversed, or an incorrect spacer ring, or any other small component to be wrong, and the whole unit you are using is rendered useless. The is mostly the case with the really cheap stuff. With high end products there is tighter quality control, and duds are very rare.

There is another possibility - did you use that focal reducer in a Newtonian/dob? These reducers will not work well in Newts, and often will result in flaring and even ghosting. These cheap focal reducers are designed to work best in refractors, SCT's and Maks. And even with say refractors, these modest reducers are only a "general purpose" item, and some small flaring will be noticeable particularly as the chip size of your camera gets larger or when used with eyepieces. For a perfectly formed, flat and pinpoint star field across the entire chip, a scope-specific reducer/flattner needs to be used. What works with a standard f/10 SCT will not work with a refractor, even if it is also f/10, and a reducer/flattner for an EP100 scope will not work with an ED80.

Alas focal reducers, just like eyepieces, do not follow the notion of "this is a scope, this is an eyepiece, it will work". Optics are more complicated than that.

As for a focal reducer for Newtonians, I've heard of one or two, but I've never seen one, and have not read reports from anyone that's used one, only "spin" from the businesses selling them, and spin is not something I base my purchasing decisions on.

Like Jeremy said, if we knew what scope you were using it in, and how (that is visual or with a camera), and maybe a photo, all of this will help us give you the best info possible for your question.

Alex.