Exploring the Focal Reducer in Visual Observations
Recently, we were testing eyepieces for side-by-side comparison and decided to try something else fun. I added an ATiK brand .5X focal reducer onto the Tele Vue 32 and 40mm plossl's respectively. This style comes in a 1.25" aperture and like any eyepiece filter, threads directly onto the barrel of the 1.25" eyepiece. I was hoping for a marked improvement in brightness and didn't really discern one.
However, the image got smaller and the contrast did improve. I was able to see some small breakaway prominences which had left the limb, a rarity without exceptional contrast. (I suppose in my slightly scuzzy skies, that this was a bigger deal than I gave it credit for at the time) This is a good option for those who don't have or want a big 2" 55mm Plossl hanging off their scope, but want a wider field of view. It offers more disc and a slightly sharper disc visually.
Then I moved onto a stock Orion brand 25mm Plossl I had laying around. In the past, I've disqualified 25mm eyepieces as too powerful, and exceeding Dawes Limit. But with the focal reducer threaded onto the eyepiece, it wasn't a bad view. While I don't recommend it as my first choice, I would give it an overall thumbs up compared to previous attempts.
I found one crummy part of the experiment to look out for, however. In moving the focal reducer around so much, I think it took on static and repeatedly introduced debris into the optical train. I had to clean it several times to keep it clear. This may just be due to the number of times I was moving it around, setting it down and such. So close to focus, the dust really shows up. So be careful in handling it or be prepared to clean and keep it clean when working outdoors.
I have not tried the extension option which is said to make the 0.5X into a 0.3X. Perhaps some other time. I checked around and ATiK still makes it. They also make a 2" version of this as well as their 1.25" I found that OPT offers a house-brand of something that looks and spec's identically. It may be made by the same optics house with another brand stamped on it. OPT charges $29.95 for their model.
........................................... It should be noted that I have tried the .63X and a .3X SCT style focal reducers and was not as pleased from their results as with this style which treads to the eyepiece. They weren't quite as sharp.