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TeleVue 8 mm Radian and Mars
by Richard Orr, April 9, 1999. Reprinted with permission.
I have been anxiously waiting for a good night to test the new 8mm Radian I bought from Company 7 last week. I had high hopes that this eyepiece would become my standard high power planetary eyepiece for drawing at the scope -- I was not disappointed. Arguably, the 1-1/4 inch Carl Zeiss Abbe ortho eyepieces that I use for the planets are the best planetary eyepieces ever made. Unfortunately, when it comes to drawing the planets, I have to remove my glasses to look through the Zeiss Orthos and then put the glasses on to draw the subtle detail that was seen. This can be so distracting that it compromises my ability to capture fine planetary detail on paper. Thus my hope for the new Radian line of eyepieces.
First light for the new Radian was on April 5th when I had a couple of hours just after dark to take the Televue 85 telescope out on the back deck. The 8 mm Radian gave me a power of 75x. Immediately, I could tell that the 8mm Radian was a well corrected, clean image eyepiece. The four stars of the Trapezium (in Orion) were nice and sharp and M42 was spectacular (when isn't it?). The star pin-points of M35 and M67 were also very satisfying. But what impressed me most on the first night run of the new Radian was how clean the star images was of Algieba (separation 4.3 arc seconds) and Caster (separation 2.5 arc. secs.) at only 75x. The high quality of both the 85 mm refractor and the 8 mm Radian makes for a dynamite match. The only planet up was Venus. I drew the planet noting some subtle disk shading using the 8mm, a Televue 2.5x barlow (188x) augmented with the use of a violet and red filters. But it was not really a pleasant experience since the constant tweaking of the alt azimuth mount due of the limited field of view at high power complicated drawing and concentrating on the planet.
The morning of April 8th was a different story. Not only was Mars well placed in the sky, but the atmosphere was very stable. My Astro-Physics 155mm EDF refractor on the G-11 mount held Mars in the eyepiece and provided me with the best view of Mars that I have had in over a decade. At 14.8 arc seconds in size this planet is ripe for observation. Coupled with the larger refractor the 8 mm Radian fulfilled all my hopes. With glasses on I was able to draw Mars at 341x (8mm Radian, 2.5x barlow, red, blue, and no filter). Although I could not compare the Zeiss (which comes in 6mm and 10mm) directly against the 8mm Radian, I could see no more detail with the 10mm Zeiss (273x) with glasses off, than I could with the 8mm Radian (341x) with glasses on. Not only was Niliacus Lacus obvious but the much more subtle western extension "Nilokeras" could be seen without difficulty. In addition, the difficult northern extension "Oxus" of Margaritifera Sinus could be seen, as could the fragmentation of the northern edge of Aurorae Sinus. The brightening (in a blue filter) of the morning and late evening clouds or mist could be made out at the edges of both horizons on Mars. Not only were astronomical conditions right for making this a night to remember but the fact that I could capture a lot of this on paper without ever having to take off my glasses was icing on the cake.
The 10 mm and the 8 mm Radian that I currently own will likely remain my planetary drawing eyepieces for the rest of my life. I simply can not see how they could be improved.
Bottom line -- Thanks for the 8mm Radian.
Richard L. Orr
Contents Copyright 1999 Richard Orr, Used by Permission All Rights Reserved