Telescope Reviews: Howie Glatter Deep Sky Binocular Filters??

Rick -

No problem, it seems obvious now. It took an "I told you so" or two (or five) before I learned to keep my expectations realistic. That was my problem with the UHC-binocular experiment - I had completely unrealistic expectations, fed in part by the misleading advertisments for deep sky and nebula filters that have the "no filter" and "with filter" photos. I was expectating a more dramatically positive effect, and I underestimated the amount of darkening the entire field would suffer. In a large aperture scope, say 8" or more, brighter field stars will shine through the filter? Correct? So the nebulosity is not the ONLY thing visible, depending on the object and field, correct? For example, if viewing the Cone Nebula with a filter, would the associated Christmas Tree cluster totally vanish from sight, leaving only the nebulosity to be seen? I expected the filter to enhance the nebulosity, darken the entire view, but leave some stars visible.

In my 100mm binocular, when I closed one eye and viewed through the filtered side only, the view dramatically darkened, leaving only nebulosity to be seen. All other stars and field stars were completely snuffed out. When viewing M42, the nebulosity was of greater extent, and some hints of texture could be detected while using the filter, but the entire field was utterly-black and devoid of field stars. Even the Trapezium appeared to mostly vanish.

When viewing through both eyes, the brain "averaged" the views and a combined effect produced a mildly-enhanced image. Nebulosity appeared to increase, but only to a marginal extent, not really noticeable unless trying really hard to notice. The view appeared darkened somewhat, but nowhere near as drastically as viewed through filter alone. This actually improved contrast somewhat and contributed to the marginal gain in apparent nebulosity, I suspect - more so than the passband's effect, IMO. I could be wrong and probably am. At any rate, the net gain was hardly worth the expense and trouble of using the filter - again, in my opinion. But, there are some caveats to my experiment :

I simply placed the filter inside the rubber eyecup which I partially rolled back. It fit snugly with no modifications. I may not have had the filter positioned 100% correct - it may have been tilted off-axis, or it might have been improperly distanced between the eye and eyepiece lens. Perhaps the Glatter filters, which has a slimmer profile (presumably they do not have the standard threading ring of 1.25" scope filter, which increases the profile of the filter), and mounts behind the eyecup, function to more positive effect. I would be interested to try them on a pair of 22x85 Ultra/Grizzly to find out.

In the end I concluded that the idea had some merit, and possibly some usefulness under better conditions than my simple, awkward trials. But several members of this forum warned me not to expect much, if anything, and they turned out to be right. That's happened more than once.

Eventually I'll learn.....

Clear dark skies...

MikeG

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Michael Gilmer - Member of the Meteoritical Society & Collector of Falling Stars.

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