Takahashi 5.7mm & 10mm UWA by Daniel Mounsey

I was glad to see Takahashi finally coming out with some wide field eyepieces of their own. I managed to acquire the 5.7mm and 10mm for this test, thanks to my friend Tamiji Homma. Both units are 1.25” with apparent fields of 90 degrees. My primary interest in the eyepieces were to evaluate axial contrast and edge performance while viewing planets and deep sky targets. It’s important to note that eyepieces behave differently in various types of telescopes, so you have to account for that as an observer. If an eyepiece is not corrected for angular magnification distortion, then it will not produce stars as sharp along the edge of field. It’s hard to believe that out of all the countless wide field eyepieces on the market today, very few if any are corrected for angular magnification distortion.

Companies like Nikon and Explore Scientific for example are paying more attention to this in the hyperwide department because it does help improve contrast around the periphery while viewing extended deep sky targets. My tests were conducted with two telescopes and no coma correcting devices at any time during my tests. One telescope was a 10” F-5 Teleport housing Zambuto optics and the other, a Takahashi FS152 F-8 flourite doublet refractor. Obviously an F-8 optical system is going reveal a more well corrected looking image across the field. Using the 10mm, I noticed that stars in the slower FS152 at 121x were very uniform and pinpoint across the field and out to the very edge. I observed NGC 457 and the contrast was absolutely beautiful with pinpoint stars. One minor issue I did notice with the UWA’s while observing is the mechanical design since the top of the eyepiece is flat. This made it a little less inviting to position the eye above the lens.

I observed several different deep sky objects using the 6” refractor and it was a wonderful match. I homed in on a couple of show piece objects such as M33 for example. Under the conditions I was in, the core stood out nicely while M71 looked like powdered sugar. The Ring nebula also had a nice contrasty pop to it that really impressed me and it made me wonder how the 5.7mm would behave on Jupiter. I then placed the 5.7mm UWA in the refractor to have a look at Jupiter at 213x and was utterly impressed with how well this multi element design could actually produce contrast like a simple ortho or plossl on axis. A wealth of detail was present such as tiny ovals, cloud belts, garlins and tiny festoons with striking color fidelity. I didn’t notice any kind of internal reflections which plague lesser eyepieces and would describe the images as a slightly more neautral visual tone.

I decided to conduct the same tests using the 10” F-5 Teleport and I expected to see slightly more aberrations using the faster optics. Like most other eyepieces, it’s a similar situation. I don’t like to use any kind of coma correctiong devices if I can help it. I think optical systems at F-5 or higher are fine without them. I started with the 10mm which would give the Teleport 127x. After going back and forth to the various star clusters an such, I was surpised at how well corrected the images were. Sure there were some slight aberrations around the periphery which I expected, but nothing I would describe as dramatic. The stars in the field had a nice iniformity about them. I did notice some slight hints of lateral color towards the edge on bright stars but once again, the overall optical quality was extremely impressive. I then decided to have another go at Jupiter with the Teleport. The 5.7mm in this scope would give 222x which is a good digit for this target. Once again the contrast and detail on Jupiter was nothing less than sensational. So much detail was visible I was amazed at the wealth of surface colors.

I must admit that over the many years I’ve been observing and testing eyepieces, I have reached a cross road in my career about wide fields. I was speaking to my friend Carlos Hernandez about this who has many years of experience and is a highly skilled visual observer. It is amazing how far wide field eyepieces like these Takahashi UWA’s for example have come. It has gotten to the point where I find myself quite happy to use them even on planets and many of you know how fastidious I am. Once again though it’s important to note that no matter how good and eyepiece is, they all perform slightly different with various optical systems and in this case, I provided some insight on how they are with a slower optical system like my 6" refractor, and a faster reflector like my 10" Teleport.

Overall, I admit the Takahashi UWA's are certainly very expensive eyepieces and will only appeal to a certain limited audience. Takahashi is well aware of this and I suppose that the yen vs. the dollar isn't helping either because it plays games with the industry. If you got the bucks, I say go for it. Takahashi has always impressed me with their quality of products and it appears to be so in this case as well. Some observers like to haggle over numbers but me, I just wonna view.

Steady skies,

Daniel Mounsey
aka Doctor D