发表于 2008-3-24 21:49:37
Review of Eyepieces for the Planets |
Zeiss Abbe Orthoscopics, Pentax SMC Orthoscopics, TeleVue Plossls, and University Optics Orthoscopics compared
I first began observing back in the early 1970's, and since then have used a variety of eyepeices to see which ones work best for observing the planets. Here is a review of some of the eyepeices I have tried.
One comparison was between the Zeiss Abbe Orthoscopics (1.25"), Pentax SMC Orthoscopics (0.965"), TeleVue (TV) Plossls, and University Optics (UO) Orthoscopics. I did not have duplicate eyepieces of the same focal length, so tried to look for overall general performance characteristics. My tests were conducted during several observing sessions using my Astro-Physics (AP) 180mm f/9 EDT refractor using a MaxBright diagonal on a variety of objects including the moon, Jupiter and Saturn, double stars, bright stars, and deep-sky objects. The seeing and transparency conditions were about the same during these observing sessions. The eyepieces I used for this comparison included an 11mm TV (147x), 10mm Zeiss (162x), 9mm UO (180x), 8mm TV (203x), 7mm Pentax (231x), and 6mm Zeiss (270x). Since there was a relatively wide range of magnifications I broke the eyepiece comparisons into six groups with some overlap: the 11mm TV with the 10mm Zeiss; the 10mm Zeiss with the 9mm UO; the 9mm UO with the 8mm TV; 8mm TV and 7mm Pentax; and the 7mm Pentax, and 6mm Zeiss.
I will start with the UO Orthoscopics (Orthos) and TV Plossls first. In general, I found the performance of these eyepieces to be fairly close. The main differences I noted was that the light transmission in the UO Ortho seemed a bit better then in the TV Plossl. For example, I was able to see fainter stars in the Double Cluster in the UO then in the TV. Also, there appeared to be a tad less scattered light around Jupiter in the UO then in the TV. The contrast on the moon appeared to be the same in both eyepieces. Whitish colored areas on Saturn and in its rings appeared a bit more off-white in the TV then in the UO.
When comparing the Zeiss to either the UO or TV, the Zeiss had noticeably better light transmission, contrast, less light scatter around bright objects, and better overall sharpness. The other differences I noted between the Zeiss and Pentax vs. the UO and TV was that the planetary colors seem more accurate. This may be somewhat subjective on my part however.
I felt that the Pentax and Zeiss were very close to each other in overall performance. It is my understanding that the Zeiss eyepieces were designed to work well with their APQ refractors, which are f/8. So if you are using them with a telescope with a focal ratio of f/8 or longer the stars are sharp right to the edge of the field of view.
I feel the UO and TV offer a lot of performance for the money however, so would not hesitate to recommend them.
Clave Plossls compared with TeleVue Plossls, Brandon Orthoscopics, and Aus Jena Orthoscopics
I first began using TV Plossls back in the early 1980's after they were introduced and Richard Berry said that they were the sharpest he ever used. They replaced the Meade Research Grade Orthoscopics I had been using for a few years. Prior to this, I had used the Huygenian, Ramsden, Achromatic Ramsden, and Kellner eyepieces that had come with the small achromatic refractors and 4-1/4" and 6" reflectors that I purchased.
Then in the mid-1980's a friend of mine recommended that I try Clave Plossls. When I compared the 17mm TV with the 16mm Clave using a 4" f/6 AP and 6" f/9 AP refractors the Clave seemed to have better sharpness and contrast than the TV, and the TV showed more scattered than the Clave. For example, when observing Sirius the TV showed more scattered light around it, so it made it harder to see fainter nearby stars than in the Clave. The same was true when observing Mars, where I could see more background stars in the Clave than the TV. Also, the Clave showed higher contrast and sharper details on the moon, planets, stars, and deep-sky objects than the TV. The TV had a slightly wider field of view, reported to be 50 degrees while the Clave were reported to be 48 degrees, and the TV had slightly better edge correction than the Clave.
Recently I did some additional comparisons between an 8mm Clave Plossl and 8mm TV Plossl using the 180mm AP. Note that the Clave was manufactured back in the 1970's, while the TV was of recent manufacture (late 1990's). I mention this because there is a general impression that the 1-1/4" Clave's manufactured in the 1970's and 1980's were of higher quality then those manufactured after Mr. Clave sold the business in the early 1990's. The objects I compared the eyepieces on included the moon, Jupiter, and deep-sky objects. Overall, although similar in performance, I would give the edge to the TV, as it had less scatter, darker sky background, higher contrast, and better light transmission then the Clave. Note that this is different than when I compared Clave Plossls manufactured in the 1980s with TV Plossls manufactured in the 1980's.
From the mid-1980's until the mid-1990's the Clave were my standard eyepiece of choice for the planets, moon, and deep-sky objects. I purchased a 6mm, 8mm, 10mm, 12mm, 16mm, and for low power use a 2" 35mm and 2" 40mm. It was during this time that I purchased and tested them with other eyepieces, including Brandon Orthoscopics, Aus Jena Orthoscopics.
I compared a 24mm, 16mm, and 12mm Brandon's with a 25mm, 16mm, and 12mm Clave on the moon, planets, deep-sky objects and stars using the a 4" f/6 AP and 6" f/9 AP refractors. The Clave had a slightly larger field of view, 48 degrees, than the Brandon's which was 45 degrees. However the Brandon's came standard with eyecups which made it easy to "tuck" my eye into to see the entire field of view. Overall, the Brandon's showed slightly higher contrast than the Clave, while the Clave had slightly higher image brightness.
In 1989 I compared the 16mm, 12mm, and 10mm Clave with the 16mm, 12.5mm, and 10mm Aus Jena Abbe Orthoscopic eyepieces which had 0.965" barrels. Note that the Aus Jena Abbe Orthoscopic 0.965" eyepieces were manufactured in the East Germany (before the Berlin wall came down and East and West Germany were reunited) and were imported into the United States. They are not the same as the Zeiss Abbe Orthoscopic 1-1/4" eyepieces that were imported from Germany in the 1990's into the United States by Astro-Physics.
When observing the Clave and Aus Jena eyepieces on the Saturn, Vega, the moon, and deep-sky objects, they eyepieces were similar in performance. The Clave had slightly better image brightness, while the Aus Jena had slightly less light scatter. The Clave had a larger field of view at 48 degrees, while the Aus Jena had a 42 degree field of view and had better edge correction.
Clave Plossls compared with TeleVue 9mm Nagler
In 1986 I compared the Clave Plossls with a TV Nagler 9mm (the original Nagler 9mm Type 1) using the 4" f/6 AP and 6" f/9 AP refractors. The 9mm Nagler had an impressive 82 degree field of view, and had better edge correction than the Clave Plossls. So it was possible to view the entire disk of the moon, and large portions of deep-sky objects like M42 and M31. However, the Clave had better light transmission and contrast which made it easier to see fine low contrast details on the planets and in deep-sky objects. I have tried some of the newer Naglers, including the 12mm Type 4 and 16mm Type 5, and these show much better light transmission and contrast than the original Naglers, and I often use them when observing and making sketches of deep-sky objects. For the planets I prefer to use Orthoscopic and Plossl eyepieces.
Clave Plossls compared with Zeiss Abbe Orthoscopics and Pentax SMC Orthoscopics
In 1996 a friend of mine recommended that I try Zeiss Abbe Orthoscopics and Pentax SMC Orthoscopics, and so I compared them with my Clave Plossls using the AP 180mm. On the planets, moon, deep-sky objects, and stars, Zeiss Abbe Orthoscopics and Pentax SMC Orthoscopics showed better light transmission, contrast, overall sharpness, less scatter, and better edge correction than the Clave Plossls.
Here is a comparison between the Zeiss Abbe Orthoscopics and Pentax SMC Orthoscopics with the TMB Super Monocentric Eyepieces.
University Optics Orthoscopics compared with TeleVue Radians
I had the opportunity to compare a 12.5mm UO Ortho with a 12mm TV Radian with the AP 180mm. The Radian had a clear advantage in terms of FOV and comfortable (20mm) eye relief. With fewer elements the UO had better light transmission, contrast, and resolved stars better across the core of M13 and showed fainter detail in M57.
[ 本帖最后由 siqingtan 于 2008-3-24 21:56 编辑 ]