Celestron 32mm Ultima LX: A Test Report

Upon seeing the sale put on this past month by Celestron for their Axiom and Ultima LX oculars, I couldn’t resist getting another one in order to add to a partial set of three Ultimas I already had. After arrival from Fedex this past weekend, I've taken out the 12 inch F/5 Meade Lightbridge and pointed the scope at the following objects: M81/M82, M104 and an elliptical galaxy (probably a Messier object) in Virgo. The sky conditions on the first night were completely clear with no wind. Light pollution from nearby city lights seemed about average (a nice pink sky color visible from the southern horizon gradually fading to about 50 degrees above the horizon). Seeing was 2 out of 10, Transparency 4 out of 10. The second night introduced a five day old crescent moon and some high cirrus clouds that slowly grew thicker for 3 hours until I finally called it a night. Views through the Celestron 32mm Ultima LX seemed clear and very sharp from the center of the field to about two thirds of the way to the field stop. Coma and perhaps astigmatism then became an issue. I hoped it would have been better than this. The shorter focal lengths of this series of oculars do seem to have better edge of field performance, especially the 17mm (the best one of the entire Ultima LX line in my opinion). A paracorr would improve the view. Contrast was good. Lateral color chromatic aberration near the periphery was minimal. To describe, brighter objects would appear to be surrounded by a thin uneven outline of blue or purple when near the field edge which was lined in red or orange in color. Objects like planets also became out of shape slightly (Jupiter almost fission in two late last summer through my 13mm Ultima LX).
But despite these minor problems, it was exciting to observe the M81/M82 pair of galaxies together within the same field of view! I could easily see mottled structure in the core of M82 at this low power. And M82 showed hints of its spiral structure despite the low contrast due to light pollution from sodium vapor lights around a nearby church.
In comparison to the Meade 4000 QX wide angle 26mm (70 degree) it did a very good job. That eyepiece would start to blur about half out from the center of the field of view. With the 32mm Ultima LX the better optical correction and longer focal length made for a larger corrected field of view.
I collimated my optics as best I could with an inexpensive Meade laser collimator and covered the optics in between views to avoid frost from forming on the secondary mirror. I mention this because collimation is important in testing oculars, and mine was not perfect enough. I experienced some trouble focusing on the Trapezium within the Orion Nebula. I determined that when I used an 8mm Ultima LX to take a closer look at the star cluster, the same focusing pattern indicated a slight noticeable error in alignment of the secondary mirror. Nevertheless, I could see five members of the Trapezium!
I read that so many people consider this line of oculars ugly and criticize due to the rubber outer housing. I don’t seem to feel this way, in fact, I prefer this when viewing in very cold winter conditions. I hate grabbing on to anything metal when it is 10 degrees Fahrenheit or colder outside. Also, the triangular (Wankel Rotary) shape of the eyepiece barrel prevents it from rolling away. Something many of us (me included) has experienced. To compare it to a Televue 27mm Panoptic I viewed through last summer at a star party it is not quite as nice (better edge of field performance), but it feels solid and of good quality for half to two thirds the price. It is a pretty good deal. I can’t wait to use it more this spring!


Clear Skies! - Stephen

I'm still thinking about completing the set by getting the 5mm and 22mm, but I'm thinking it over and taking things slow.

The second night introduced a five day old crescent moon and some high cirrus clouds that slowly grew thicker for 3 hours until I finally called it a night. Views through the Celestron 32mm Ultima LX seemed clear and very sharp from the center of the field to about two thirds of the way to the field stop. Coma and perhaps astigmatism then became an issue.

StephenL Thanks for the review, I suspect you will enjoy this eyepiece.

As far as coma goes, coma is inharent in an F/5 Newtonian, it's there and the only way to eliminate it or at least significantly reduce it is with a coma corrector like the Paracorr. It is hard to distinguish between astigmatism, coma and a curved field, particularly when it is not just one but a combination. The curved field can be eliminated by refocusing when viewing the edge but that still leaves the combination of coma and astigmatism to deconvolve. Coma looks like those little sea gulls but astigmatism (different focal lengths on different axis's) are crosses or lines depending on where they are focused. Figuring out exactly what is going on is just not easy.

The other problem is that many of us have small amounts of astigmatism in our eye lenses that only shows up at the large exit pupils, your 32mm in the F/5 provides a 6.4mm exit pupil. So this is another aberration to add to the mix... This typically shows up as Spiky/Flaring stars, if you are seeing this then rotating your head to see if the flares move will tell you if you are seeing astigmatism in your own eye.

Main thing... enjoying the eyepiece for what it does do rather than being disappointed in what it doesn't do... (Paraphrasing John Wooden)

Jon Isaacs

Excellent review Stephen. There is little information available on the Ultima Lx eyepieces. If I might suggest breaking the review down a bit in paragraphs for easier reading. These old eyes strain mightily with the small font that must be used. Thanks again.