I recently bought an Explore Scientific 3″ Field Flattener .7x Reducer from Highpoint Scientific and was able to test it out having a clear sky last night. My scope is the Explore Scientific 127MM ED Essential Series with a ZWO MiniEFW and a ZWO ASI-1600MM-Cooled camera.
I was so impressed on the flatness of the field and stars are pin sharp up on the edges. Unfortunately it was full moon last night and I’m also living in a place where light pollution is a real problem, and the image below is all the best I can get.
Before I continue, I’d like to give the Highpoint Scientific Team a shout out. Their service is top notch and willing to entertain and answer any question.
Above is the image, a total of 10 subs x 5 mins exposure using Hydrogen Alpha (Ha) filter. My capture software and pre-processing software is Nebulosity 4.1.2 and for post processing, I used Photoshop CC 2017.
I have been using the Explore Scientific 0.7x Reducer/Flatter for a couple of my sessions and below are the images.
Giving more information specially to some of the comments below. I have captured and photo of the distance between the camera and the ES 3″ .7x Reducer Flattener.