Design: Variable polarizing filter
Description: 1¼ inch variable filter
This filter allows you to control the amount of light coming through by simply twisting the bottom portion of it. This feature makes it a little more useful than your average moon filter that has a set tint. With the ability to control the tint you also gain the advantage of using this on a wide variety of targets. For example you can make it extremely dark when viewing the full moon but lighten it up a bit when you swing your scope towards Jupiter or Venus. The control allows you to cut down on the glare really bright targets tend to create.
The filter is well constructed and made in Japan. It is basically two filters stacked on top of each other and it is threaded on only one side. The filter also ships with a small plastic case for storage. Perhaps the nicest features of this filter are its incredibly small size and lightweight (compared to other polarizing filters) and the extremely smooth action. The filters range is between 40% and 3% blockage of incoming light. To adjust the brightness simply rotate your eyepiece in the focuser or diagonal. The directions also explain how it is possible to separate the filter into its two components for daytime observation (I have never tried this). The separate filters are not actually darker but they will cut down on glare produced by the suns reflection on surfaces such as water or glass.
My experience with this filter is basically confined to lunar and planetary observations. I find it extremely useful for the moon simply because the moon does not stay at a constant brightness throughout its cycle. When the moon is brighter I have the option of turning the filter up until I reach a comfortable level. I have found that with the filter in place contrast is greatly enhanced on the moon, particularly near the terminator. I also use it on Jupiter sometimes when observing with a high focal length eyepiece (25mm – 40mm). These eyepieces tend to create a lot of glare and the filter allows me to cut a little of that out. Also when used with my refractor false color is less of an issue when I have the filter in place.
The only real downside to this product is its cost versus a regular lunar filter. It is basically twice as expensive as an average lunar filter. Other than that minor issue I really do not see any other reasons not to own one of these.
Like I said previously if you can afford the extra $10.00 this filter is probably worth it. It really all depends on how much time you spend observing the Moon, Jupiter, Venus, or daytime scenes. Like most filters do not expect to get a ton of use out of it. However it is extremely useful to have around for those days when the Moon is high in the sky and begging to be viewed. On a scale of 10 this would get a 6 or a 7. This rating is not based on its design or construction but on its overall value in my collection.
Submitted by Curt Irwin – firstname.lastname@example.org - Grand Rapids, Michigan