都是PL，就不再另外发帖了。
Televue Plossls 15mm, 11mm, 8mm
By Timm Bottoni - 10/28/2005
After searching the Internet for articles and reviews on eyepieces, I discovered that there is not a standard way that eyepieces are reviewed. The problem is that everyone抯 approach is different, and everyone's experience level varies, so the results can be dramatically different from one person's opinion to another's. I found a great article on Cloudynights.com that really helped explain some of the criteria to use when evaluating eyepieces titled, 揘otes on Eyepiece Evaluation?from Michael Hosea. From this article I listed the optical criteria that I felt were critical, and assembled them into a chart to use while I tested each individually and compared them to each other. The article provides excellent advice on what to look for, and how to go determine what negative properties to look out for, what positive properties to look for, and other issues that might come into the mix. The problem was, as the author pointed out, that things like brightness, contrast, and sharpness can be deceivingly difficult for the human eye to judge. Now when we take into consideration the scope being used, its aperture, its focal length, and corresponding focal ratio, the quality of its mirror or optics, and seeing conditions, I choose to rely on good old-fashioned advice from experienced fellow amateur astronomers who I knew I could trust.
| | Side view of Televue Plossls showing relative sizes |
I decided on the Televue Plossls (15mm, 11mm, and 8mm) for several reasons. First, they were about the right sizes that would provide me with a good range of medium to high magnifications with my scope. Second, I couldn抰 find a single negative thing said about them, anywhere, and even though I couldn抰 find a comprehensive review, I consistently found the opinion that the TV plossls, along with the Celestron Ultimas (and similar models) were always rated as the best overall reasonably priced plossl eyepieces to get. And with Televue, you are almost guaranteed that you will lose the least amount of resale value, if you ever sell them. Televue is also the only company that I know of that will repair an eyepiece (at a charge of course) should you need one repaired.
| | Top View showing multicoated lens element |
Dealing with Anacortes is a pleasure; fast response to emails, shipping on time, and FedEx ground tracking make for a pleasant stress free shopping experience. (No, I don抰 work for Anacortes, or Televue, and this review and opinions herein are totally my own, based on my experience, scope and viewing conditions). My Televue eyepieces arrived on a Saturday (one of the advantages of FedEx Ground is that they do Saturday deliveries as part of the regular schedule) and I eagerly tried them out that night. I already had a Meade 4000 series 26mm plossl, an Antares 6mm ortho, and a Celestron Ultima Barlow, and had previously owned and used the Celestron Nexstar kit plossls, so I was reasonably sure I could tell if these were worth the money.
The three TV plossls gave me the following magnifications without and with the Barlow on my 80mm refractor (500mm focal length, F6.25). It turns out the Ultima Barlow is not 2X but actually 2.5X in my scope, but that抯 for another review.
TV 15mm ........ 33X ... 83X
TV 11mm ........ 45X ... 114X
TV 8mm ......... 63X ... 156X
Using the criteria I extracted from the 揘otes on Eyepiece Evaluation?article I created the following chart. I ranked then in the simplest way I knew how, the old A,B,C, school grading system, and gave them a final grade. I needed a way to judge things as objectively as possible, so I created two charts that I could hang on the basement wall, and illuminate from a strong work light to attempt to eliminate as much external error as possible. Next I used my Canon 20D, 8.2Megapixel DSLR, along with my WO Megrez II 80 SD on a sturdy tripod to record shots and compare them on the computer, which allowed me to magnify the images to outrageous levels, and try all sorts of things that would require a much longer article, and a course in Photoshop to understand.
Due to size requirements, the high-resolution pictures, and the computer geek processing stuff will be left out of this article (OK, you can breath a sigh of relief). I have included a low-resolution image of the two charts so that you can see the approach I took. One is a 1cm grid printed in high resolution and tiled across one side of a large foam board, and the other is a high resolution photo quality lens chart used by lens testing gurus to determine the quality of camera lenses.
The chart criteria turned out as follows:
I also observed on a clear steady night and used the Double Cluster to compare to my basement tests. I also tried a couple of other objects, including Mars of course, the Plaiedes cluster, some DSOs and several double stars.
The short answer:
A - / B+
I could clearly tell that these were better than any of the other plossls I抳e ever tried, and I was very pleased with the views through my telescope, but there are some minor reservations.
The long answer:
On the Double Cluster - Edge to edge sharpness was excellent. To my eye, either a star looks sharp all the way to the edge of view or it doesn抰. The Meade I have isn抰 bad, but once the stars of the Double Cluster got near the edge, they became soft. When I compared the barlowed Meade 26mm to the 11mm TV plossl, there was no question that the TV plossl performed better. Surprisingly, when I compared the barlowed 15mm TV plossl to the 6mm Antares ortho, the TV looked brighter (perhaps due to its larger field of five and longer eye relief), and appeared to have just as good of contrast and sharpness. All three plossls performed the same to my eyes at night, both without the Barlow and with.
On Mars ?the view through all of the TV plossls, even barlowed were better than I expected. I could make out some details, and with the barlowed 8mm TV plossl, I was able to see more than I expected. I did notice the evil ringing of some false color in my refractor with Mars, so I decided to bring out the WO 1.25 inch violet reduction filter. The filter did its job and removed the violet, but when its used with the Barlow it also creates a ghost refection that is noticeable but tolerable. Since it抯 a function of the filter/Barlow combination, I don抰 consider it a defect in the eyepieces, as it was apparent in all three.
On the Moon ?the TV plossls looked great. I was able to see loads of details, and was pleased with the views of all the eyepieces both with and without the Barlow.
I tried the TV plossls on other objects as well, including double stars, open clusters, globular clusters, and the Andromeda Galaxy. In every case, I experienced the sharpest views I believe are possible from the Megrez 80 II SD.
I would say that without question these are excellent eyepieces and are worth the price to me (especially considering the sale and rebates). I think that as long the telescope you are viewing with has at least average or better optics, these would perform well. That said, there are some things that I didn抰 like, and some aspects that any purchaser needs to be aware of when buying them, so I抳e summarized these into the Likes and Dislikes below.
THINGS TO BE AWARE OF
These have only a 50 degree field of view, which is pretty standard for plossls, but not very wide when compared to other designs, so I had to give them only a C for this aspect.
They have an eye relief that is relatively short (again this is characteristic of the plossl design), and depends on the length of the eyepiece, at a ratio of about 70%, which means that if you wear glasses you might find these hard to view through.
LIKES
Optically excellent ?bright, high contrast, sharp images, and generally pleasing to look through. My photo test results revealed outstanding sharpness as well, with no optical defects like pincushioning, or distortions of any type. The coatings seem to do an excellent job, and the glass is clearly very high quality. All three had equal quality based on both my photo tests, and my viewing tests.
Parfocal ?I found myself wanting to focus while switching between eyepieces but didn抰 really need to ?according to the Televue website, these are parfocal with all B parfocal series TV eyepieces, which includes most Plossls, the Radians, a couple of the Panoptics, and many of the Naglers (see Wing Eng抯 Astromart review of Televue Parfocal eyepieces for more information on this topic).
Barrels are threaded for filters, and cleanly done, so filters screw on easily.
Barrels have a safety stop ring, which prevents the eyepieces from coming out without loosening the retaining screw significantly and deliberately removing them.
They are sized proportionally to each other, in length both out of a tray, and in the holes of my tripod spreader tray. This makes it really easy to tell which eyepiece you are using in the dark when you can抰 read the letters labeling on the eyepieces. I could tell one from another both while sitting on their own, and while sitting in the holes of my tripod tray (not to mention in my coat pocket when its cold out)
DISLIKES
(OK, I know this is nit picking, but it抯 all I could find wrong with these eyepieces)
The eyecup could be softer, and feels a bit plastic like to me. Its hard to roll down and hard to remove, and even harder to put back on.
The caps could fit better.
The eyecup cap is too loose, and the barrel cap is too tight.
The silver barrels unscrew a bit too easily, and I found myself unscrewing the barrel from the eyepiece when I was trying to unscrew the filter from the eyepiece.
THE BOTTOM LINE
If you don抰 wear glasses for viewing, don抰 mind a 50 degree field of view, and have a need for these three focal lengths, buy the set, whether Mars is close or far, because these are definitely excellent eyepieces for the price. |
置顶卡
变色卡
千斤顶
显身卡
