The Celestron C90 Maksutov Cassegrain Telescope
Mar 02 2015 05:00 PM by skyaddict
William Optics Zenithstar 71ED and Twilight I M...
Feb 28 2015 10:53 AM by Ahab
If you want to Master your craft, read Lessons...
Jan 07 2015 11:29 AM by AstroDad
Celestron Ultima 80
Dec 16 2014 05:54 PM by Gianluca67
Categories See All →
- CN Reports
- User Reviews
- How to . . .
- Observing Skills
- Astronomical History
- Optical Theory
- Vision and Related Experiments
- How to Gain the Support of your Family for your Astronomical Pursuits
- Evaluation Tips
- Special Events
- The Elements
- New Articles in [!monthname!]
- Telescope Articles
- Submit a Review / Article
- Monthly Guides
- Behind the Scenes
- About Us
- Copyright ©
- Terms & Conditions
- Tiny Eyes on the Skies
- From the Editor's Desk
- What's Up . . .
- The Light Cup Journals
- Who is this Super Light Cup?
- Cloudy Nights T-Shirts
- Imaging Contest
- Small Wonders
- Previous Imaging Contest Winners
- This Month's Skies
- Mike's Corner
- The Cloudy Nights Friends and Family Discount
- Uncle Rod's Astro Blog
- Fishing for Photons
- Binocular Universe
- Article Submissions
Televue 7.4 Plossl VS Edmund RKE 8mm
Voice your opinion about this subject in our forums
Televue 7.4 Plossl VS Edmund RKE 8mm
by Larry Beach
|Click on the images to load a larger version|
Well I have finally done it, I tested my venerable TeleVue 7.4 up straight on with my Edmund 8mm RKE...
I have always liked the RKE eyepiece set, Over the last 40 years I have used every darn eyepiece under the Sun it seems. Last night the seeing was fairly good for the Midwest, even tho it was mostly bumpy, there were times (about 2 seconds each) of absolute superb clarity. Saturn was perfectly placed at 10:45 CST, shining a beautiful Golden yellow. Arcturus was above and to the East a Bit.
I knew it was going to nice when I briefly looked at Izar (Epsilon Bootes) and saw a nice clean separation of it's Golden Primary and Saphire Blue secondary at 2.8" apart, It has always been my favorite double. I did not use my 127mm Mak because the secondary Star lies in the defraction ring.
The telescope I was using was my Celestar 8 Deluxe, built in Approx the year 1998, I know this because it was built before the Factory defective P.E.C. chip was replaced by a chip with revised software that trained the drive for the full revolution of 5.41 minutes not 4.00.
I tried the Televue first, as it has been a go-to Planetary eyepiece for the 13 years I have owned it, (to have an eyepiece stay in my kit that long it had to have prooven itself. The Stars looked wonderfull, nice contrast and the space between the two was Black as Coal, I did not see much of any difference between the two eyepieces except the expected difference in power, the TeleVue being 270X, and the RKE at 250X. Since both eyepiece were viewing "on axis" the field edges did not come to play.
I gave color rendition a slight edge to the TeleVue. After drooling over Izar for about 20 minutes I knew I had to move to my main target of the evening Saturn!
My first looks showed the ring system opened beautifully at Approx, 18 degrees Perfect! The globe cast a razor sharp shadow on the rings. Casini's devision was tac sharp and I could follow it all the way around. I could even see hints of the elusive © "Crepe" ring! It wasn't standing out like a sore toe but it was detectable none the less, and here is where I got my first shock of the night, I could see it better with the Edmund RKE!
Another stunner was the fact I could see 5 of Saturn Moons! I could see the dimmest with direct vision Enceladus shining dimly at -7.04 This normally would not be an issue but I was viewing from my light polluted back yard. Titan was glowing Orangish at -4.94 from the cold Methane in its Atmosphere.
I was a little stunned that I had to use averted vision using the TeleVue eyepiece to view the dimmest Moons. Saturn globe was A Golden Yellow with low Contrast belts in the temperate zones they were an orangish Brown tit lite white streaks in them. The Polar region as an Olive green mixed with tan also with slight White streaks. I wonder if we are going to be treated to some Storms on Saturn this year like we were the last couple years? Lets hope.
I was to say the least a bit dissapointed in the performance of the much more expensive Televue lens compaired to the $59.00 Rank Kellner. On the other hand you could say the RKE performed much better than expected, even WITH my eyeglasses on!In conclusion:
You cannot go wrong with TeleVue products. They are built to the highest of standards, the 7.4 being no exception. It has very good contrast and color correction. I did not test the edge sharpness, but it is a fact the 3 element RKE is a bit brighter, and every bit as sharp on axis. My 8mm is an older one as is the whole set I have. I don't know if they are built to the same standard now. (that isn't a question with the TeleVue).
If you have never owned either I highly suggest both, especially the RKE at nearly 1/2 the price If you are on a tight budget. The 28 is a must have lens! It has a quite unique "Floating" Effect with objects if you back off the lens a bit and let your eyes softly defocus a bit.