TeleVue Radian 14mm, 6mm, & 4mm Review
By: Vlad Fedosov
I don’t quite remember when my first encounter with the Radian eyepiece line was, but this is not the first. I do remember using them with my old-school TeleVue refractors so this must have been sometime in the early 2000’s(when I owned my original green TV-85 and white NP-101). Having come across a set of 14mm, 6mm, and 4mm Radians almost 20 years later I was eager for the opportunity to take them out on a real test drive and evaluate them! The Radian eyepieces are primarily a high-power eyepieces with a modest 60° field of view(FOV) boasting a very good 20mm eye relief. Why would one want a 60° FOV eyepiece when 82° and 100° offerings are available these days? Read on to find out!
I evaluated the eyepieces at my simi-dark sky house in the NW. The scope used for the test over several nights was a Takahashi FS-128 F/8 APO refractor. The main targets used for the evaluation were Jupiter, Saturn, and the Moon. I did also observe several double stars. To make this somewhat subjective I tested the Radians against my Baader Classic Orthos(BCO). Why the orthos? Well, both eyepieces are more of a double star/planetary piece of glass.
If you have not read any of my reviews or watched any of my YouTube videos one thing that I want to get out of the way is that I do not like eyepiece eyecups! Why? Its because on most eyepieces the eye relief is not sufficient enough to have the eyecup up and have your eye close enough to the eyepiece to see the entire FOV while not at the same time bumping the eyepiece and introducing vibration. This is one place where the Radian line shines! The eye relief is so long with them that I can comfortably have the eyecup up and still see the entire FOV. They also have a telescoping barrel that extends out to make the eyecup even higher but I have always found this to be a gimmick. I do not wear eyeglasses and just having the eyecup up is plenty enough to take up the excess eye relief. If I was an eyeglass wearer I would still have the eyecup down I’m sure!
The other very nice thing about this eyepiece line is that the eye placement is quite forgiving. Basically there is not that high a chance that when you move your eye off axis a bit that you will see blackout. Overall I would say that this makes it easy to observe with for extended periods especially compared to the orthos. Sharing the view would be much better with Radian than ortho, especially with new observers. I often find that they struggle to see anything in an eyepiece with a tight eye relief, while with a Radian it would be much easier. Ortho also have a nasty habit of fogging up(depending on the season) as your eye is so close to the eyepiece because of the short eye relief.
So now that we have talked about some of the uses and comfort factors of the Radian vs the ortho what about the optical performance??? Well, the best thing that I can say is that a critical eye is required to see any difference in contrast or sharpness. The one difference that is pretty obvious is that the Radian do have a wider FOV at 60° compared to the 50° of the ortho. After much scrutiny between the eyepieces and especially comparing the 6mm Radian to the 6mm BCO the ortho does provide a consistently better view of Cassini division and the banding on the planet is more pronounced. On jupiter, I did notice that the view was more similar but the ortho did show a hair more contrast on the banding. Overall the views are very similar but I did feel that the orthos did provide a hair more contrasty and sharper view.
For double-star work the Airy disk is a bit more pronounced with ortho. The overall view is hands down better in the Radian. Why is this you might ask? Simple, it’s just so comfortable to observe with the Radian. So for double stars, I would prefer the Radian as the views are just too similar optically.
So what is the conclusion on the Radian eyepiece line? Well, I would say that if your an eyeglass wearer this line is made for you! The Radian line has a very good eye relief while also having very sharp optics! If you do not need the really long eye relief I would say that a quality ortho like the BCO is a better choice as they are less expensive and overall a tad better optically.