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Orion V-Block Anti-Fringing Filter
| Brand | Orion |
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| Availability | available |
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Reviews
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Feb 28, 2010
Performs as it was designed to do; with some issues.
Pros:Aids effectively in reducing CA and killing purple fringing. Workings fantastic on Venus!
Cons:Makings objects appear yellowish. Mutes detail in the Jovian belts.
Comments:Being a refractor buff of sorts, I have a small collection of various focal length refractors that perform quite within their Dawes Limit using moderately priced oculars. Nevertheless, it is the medium to fast systems in my collection that usually needs help with it comes to CA and purple fringing, which prompt my purchase of a 1.25" V-Block fringe filter.
Bottom Line: Would you recommend this item? Yes
I purchased my Orion V-Block filter at a great price of $36; used and in pristine condition. It comes in a typical style clear filter case nestled in a dense foam insert. The coatings appear metallic in nature casting a yellowish and magenta reflection. The filter is encased in an aluminum metal housing that is threaded to connect to the barrels of most threaded 1.25" eyepieces; though I did find it a bit difficult to attach to a Siebert 4.4mm StarSplitter eyepiece.
At the time of my test, the telescope I used was a 90mm f/11 refractor. The eyepiece was an 8mm TeleVue Plossl, which are good all around performing ocular. Objects of choice were Venus and Jupiter.
My initial view was of the planet Jupiter using the 8mm TeleVue Plossl. At a magnification of 125x and without the filter, the image was sharp revealing good detail. But, there were some CA and a good amount of purple fringing. Contrast was good as well. After installing the Orion V-Block filter, all signs of purple fringing were nullified. CA was reduced significantly, but not completing. Though I was able to attain a sharp image, I noticed that contrast had diminished. The festoon detail became washed out and seems to blend into the brighter temporal belts. The planet also took on a false yellow tinge. Despite the faults, Jupiter was still a very good site to see in this eyepiece. I then moved on to Venus, which was showing a moderate crescent phase, similar to a 4 day old moon. Without the the filter, CA and purple fringing were quite prominent being that Venus was about 20-degrees above the horizon and still quite bright. Yet, once I employed the Orion V-Block filter, all CA was gone from the 90mm f/11 using the TeleVue 8mm Plossl, as well as the fringing! The image was sharp, too! I could also make out some irregular dark areas along the planet's terminator that I have never been able to discern before! It was one of the best views if Venus I had seen through any of my refractors!
I have more tests to do with the Orion V-Block filter. Saturn is another target I have in mind, for which I will report on soon.Mar 22, 2008A good filter for fast achromatic refractors!
Pros:Removes CA; Works well with a variety of eyepieces.
Cons:Gives everything a yellowish tint!
Comments:Many people are bothered by the chromatic aberration in fast achromatic refractors. Some, it seems, more than others. When I ordered my Orion 100mm f/6 refractor tube assembly last year, I ordered one of their V-Block Anti Fringing filters in the 1 1/14" size at the same time.
Bottom Line: Would you recommend this item? Yes
For me, chromatic aberration has to be pretty bad to be really annoying. It just never has seemed to bother me much except in a couple of quite fast (f/4) "comet hunter" refractors many years ago. As I have quite a collection of old eyepieces, I decided to do this review testing the use of this filter with a variety of eyepiece types and focal lengths.
First, I decided to use three objects for my testing. I chose the Moon, Sirius, and M42. I decided to include M42 because the individual stars are much fainter than the other two objects, and I wanted to see the effects of the filter on objects just at the limit of detection.
In all eyepieces tested without the filter, a green halo was apparent around the Moon's edge. To me, this was not that objectional, but to many it probably would be. Upon installing the filter, the green halo completely disappeared in all eyepieces. This is due to the filter removing the violet end of the spectrum. Also, by removing the violet, the filter introduces a definite "yellowish" cast to everything. I would say the view was reminiscent of looking through an APO, but with a yellowish tint.
What really surprised me was the performance of older eyepiece types with the filter. For my tastes, the best views obtained were with some old University Optics Orthoscopics. I tried a 25mm, 18mm and 12.5mm and was quite pleased with the sharpness and good contrast. I then switched to several old Kellners of 40mm, 25mm, and 18mm. I was astounded that the Kellners gave a performance that was on par with the Orthoscopics - good sharpness and excellent contrast! It's amazing what some of these older eyepieces can still do in a good telescope! I also tried 20mm and 10mm Modified Achromats (MA) and a couple of Plossls of 20mm and 12.5mm focal length. I find the Plossls and MAs to be almost exactly the same in performance. Just for laughs, I even tried an "ancient" 50mm Ramsden. The performance was still pretty good but with a very narrow field!
For me, except for the lack of CA, the really noticeable difference between observing the Moon with and without the filter is in the area of contrast. I think, when you take away the violet portion of the spectrum, you definitely lose some contrast in the darker areas. The view was still pleasing with the filter, but I think its usage would depend of what your observing intentions are! Others may see this differently!
On Sirius, the effect with all eyepieces was more like that of an APO. The bright purple flare that I would usually expect to see in a star this bright was gone. All of the same eyepieces gave good performance on this object.
On M42, the situation is completely different. I wasn't really looking for the nebulosity here, but rather the performance on fainter individual stars. Here is where I think the performance is definitely better without the filter. Of course, it's not really necessary with these faint stars, but I felt the contrast suffered here. Individual stars at the limits of visibility would fade in and out with the filter in use, while being solidly there without the filter! So it's evident that you need to pick your targets carefully if you are going to use this filter.
I do recommend this filter for use on fast achromatic refractors if you are bothered with CA. But I think that each person will have to decied for themselves when and where to use it!Sort by
