...for my field flattener for my Explore Scientific 127mm FCD100 CF APO. I have two other flatteners including the ES designed for the 127mm and the Hotech beats them both hands down for flattening the field from corner to corner. Thanks to a well known YouTube astrophotographer I purchased this piece of glass not knowing what to expect. I was pleasantly surprised after using it for two nights. After reviewing my raw data the field was flat with round stars across the entire image corner to corner/edge to edge. Well worth the purchase.
My primary purpose in purchasing this flattener was to reach the little extra back-focus needed on my ES ED102 that the 2 extender tubes didn't quite provide. In short, it solved my back-focus issue, provided a more stable image train connection to my focuser, with the added bonus of an exceptionally flat/sharp image edge to edge, all at an economical price.
Works perfectly. Removes 100% of all field flattening issues from imagery. Completely satisfied
Low price? can't be good!? I have a 229.00 one that isn't near as nice as this one. This is my favorite. What I really like is it's a FF but not a reducer. I'm using it with a 6" refractor. (F8) and a friend with a 127mm refractor recommended it. My stars are TACK sharp corner to corner. (not so with the other famous brand .8 FF reducer).
I had high expectations from this flattener. It did make the field flat but the optic I recieved was quite dirty evidently reight out of the box. The flattener resides in the light path at just the right place so that even the smallest particle of dust shows up a a huge mote in the light frames. I counted over 18 motes in my subs! Very dissapointed. This thing is impossible to clean also. The optics lie deep in the SCA section and cannot be reached to clean.
This flattener works great on my Astro-Tech AT111-EDT (f7). I have always had a problem with centering the camera in the 2" focuser compression fitting. The design of this flattener insures that al of the "slop" in the focuser is taken up and the imaging train is then centered perfectly, every time. The flattening effect is absolutely superb and appears to be well-matched to my refractor. I get nice, rounds stars across the entire KAF-8300 chip of my camera.