Celestron F/4 reducer

Hi, does anybody used or have more info about this part:
Celestron f4 Focal Reducer #93570

I have one bought with old C5+ along with other accessories, but cannot find any documents about it application, performance, etc.
OK, it is obvious it is focal reducer, but does anybody have experience with it, comments?
Thanks!

Hi Delyan,
These f/4 Focal Reducers were not ment to be used with the 5" SCT's but were in fact a FR for the 500mmm Mak/Cas spotter that Celestron sold in the early/mid 90's (NOT to be confused with the C-90 tube's). These spotters were sold by everyone from B&L to Orion. With that said, one can do some interesting things with FR lenses. I have a few old ones from the 70's I've used successfully with a number of scopes as photo aids (and even a few for visual). Like most FR they do ad quite a bit of field curvature - they are not field flatteners - and are best photographically then visually.

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