Focal Reducer Experi-ment
The Celestron Focal Reducer is a great product, designed to change a telescope from f11 to f7. It simply screws into the visual back of an SCT followed by the star diagonal and eyepiece.
by Humanoido
This means more of a large object like the Moon will fit into the field of view when looking through the telescope's eyepiece. Exactly how much more of an object, like the Moon, is visible with the Focal Reducer in place? This experiment will qualitatively determine that result.
Results are shown at the left. The top image highlights the Moon imaged through the eyepiece without a focal reducer. The Moon has a much larger image scale and does not fit into the field of view. Below, the image highlighted was taken with the focal reducer in place. The Moon just fits into the field of view. The focal reducer is one that offers edge correction for SCTs that are not already corrected. Telescopes like the EdgeHD are corrected to the edge and Celestron does not recommend using this focal reducer. However, it works well, and the author bought it for CCD use which covers only a small center area which is fully corrected. All in all, the image is rather good at the edge, even the focal reducer was not recommended.
Keep in mind this experiment was performed with the supplied Celestron stock 23mm eyepiece which appears to add color fringing aberrations with or without the focal reducer. Also, the hand held iPhone Xs Max camera adds numerous lenses into the optical train which may cause reflections, differences in lighting and focus issues depending on the orientation.
Celestron 14" f/11 EdgeHD CGX-L
Celestron Luminos 23mm FL Eyepiece 2"
Celestron Star Diagonal
Celestron Focal Reducer f/7
Apple iPhone Xs MAX
*Image experiment on Thursday evening, March 21, 2019 at 8:05 pm local time, through clouds and haze, camera was hand held, no drive, shot indoors looking out to the sky view
https://space1usa.blogspot.com/2019/03/space1-singularity-observatory-indoor.html
