Maybe the Best Kept Secret In Nebula Filters! Part II
The filters were shipped out to me on Monday, and arrived on Wednesday. Preliminary tests showed that they seem to: Darken the background sky nicely, Allow a good amount of light through (compared to OIII filters for example), And I like the way they render most stars a hot purple-ish hue (it's a nice change from the usual green of all other filters).
Since their arrival, several weeks ago - I've had quite a few opportunities to use them. And, I really like them!
OK, so I was going over my Astronomy notes recently...And realized, that I left out some interesting technical details about these nebula filters while haphazardly writing my original Post. So, in re: to the GCE nebula filters, from DGM Optics - Here's some more details, along with my comments in Purple - (this info is directly from DGM Optics):
"The Galaxy Contrast Enhancement™ filter aids in the visual observation of galaxies and milky way dust clouds and dark lanes. The GCE filter takes a different approach to enhancing galaxy observation by allowing high transmission through nearly the entire visible spectrum while rejecting only the harmful light pollution wavelengths. Because of those attributes it also is a very good general purpose LPR filter, unlike traditional wideband filters, which exclude most of the red portion of the visible spectrum. I like this very much, because until now, you couldn't "have your cake & eat it too" - If you used a broadband filter, from other manufacturers, some of the desired wavelengths were getting blocked as well.
Specifications
The GCE filter design stresses maximum optical throughput utilizing state-of-the-art optical thin-film designs and materials. This filter is a “first surface” hard oxide thin-film and is much more durable and long lived than laminated “soft film” designs used by several famous makers."
The filters were shipped out to me on Monday, and arrived on Wednesday. Preliminary tests showed that they seem to: Darken the background sky nicely, Allow a good amount of light through (compared to OIII filters for example), And I like the way they render most stars a hot purple-ish hue (it's a nice change from the usual green of all other filters).
Since their arrival, several weeks ago - I've had quite a few opportunities to use them. And, I really like them!
OK, so I was going over my Astronomy notes recently...And realized, that I left out some interesting technical details about these nebula filters while haphazardly writing my original Post. So, in re: to the GCE nebula filters, from DGM Optics - Here's some more details, along with my comments in Purple - (this info is directly from DGM Optics):
"The Galaxy Contrast Enhancement™ filter aids in the visual observation of galaxies and milky way dust clouds and dark lanes. The GCE filter takes a different approach to enhancing galaxy observation by allowing high transmission through nearly the entire visible spectrum while rejecting only the harmful light pollution wavelengths. Because of those attributes it also is a very good general purpose LPR filter, unlike traditional wideband filters, which exclude most of the red portion of the visible spectrum. I like this very much, because until now, you couldn't "have your cake & eat it too" - If you used a broadband filter, from other manufacturers, some of the desired wavelengths were getting blocked as well.
Specifications
The GCE filter design stresses maximum optical throughput utilizing state-of-the-art optical thin-film designs and materials. This filter is a “first surface” hard oxide thin-film and is much more durable and long lived than laminated “soft film” designs used by several famous makers."
I'm also very happy about this, no one wants a light pollution filter with a surface that will deteriorate over time.
"They are also much less prone to the internal reflectance problems that plague laminated filters. Laminated filters can produce a very undesirable “doubling” of stellar images often with one of the doubles being red.
"They are also much less prone to the internal reflectance problems that plague laminated filters. Laminated filters can produce a very undesirable “doubling” of stellar images often with one of the doubles being red.
Contrary to popular belief, this image doubling is not due to the red sideband component that many nebula filter designs produce, but in many cases is due to laminated glass not being exactly parallel to the protective cover plate after lamination. Many laminated filters display this annoying characteristic." This is awful! After learning about this, why would anyone buy an inferior nebula filter again? I won't be!
"This filter averages around 1% Transmission (optical density of 2) through the rejection region from 540 to 590nm, and average transmission greater than 90% Transmission in the passbands, and greater than 75% at the 656.3nm H-Alpha line. The design yields a filter with a very symmetrical shape and high optical throughput, for maximum enhancement of nebula with a minimum of loss of stars in the field of view.
The substrate is quartz and has measured total wavefront values of .25 waves. I find this fact awesome :) These filters don't use plain glass as their substrate; it's Quartz!
The combination of first surface optical thin-film technology and a polished, flat substrate enables this filter to be used with high magnification, a real plus for small planetary nebula." And, finally, this last part - about being "a real plus for small planetary nebula" It just so happens, that I have become very interested in hunting planetary nebula recently; so, I was also happy to read this.
As for me: One of the joys of using this GCE filter - Is that I simply leave a pair of them screwed into the threaded EP barrels of my Garrett signature series 10x50's - And, I just leave them attached all the time. I don't find my views of Asterisms, or Open Clusters darkened very much at all. Yet, they improve the views of all DSO's at same time. I plan to do a side-by-side comparison of these, vs. the pair of Zhumell OIII filters I have, and post my findings.
It would be great, if someone who has other name-brand "Broadband" LPR filters could also do some tests vs. the GCE filter...
The smallest (good-quality) Binoculars I currently have, are my Garrett 10x50's. But, I believe that these would also perform well on smaller Binos - Which would be great when scanning for/observing large, diffuse DSO's. In fact, I believe I just gave myself an idea for a future project...
Clear skies!
-Al
"This filter averages around 1% Transmission (optical density of 2) through the rejection region from 540 to 590nm, and average transmission greater than 90% Transmission in the passbands, and greater than 75% at the 656.3nm H-Alpha line. The design yields a filter with a very symmetrical shape and high optical throughput, for maximum enhancement of nebula with a minimum of loss of stars in the field of view.
The substrate is quartz and has measured total wavefront values of .25 waves. I find this fact awesome :) These filters don't use plain glass as their substrate; it's Quartz!
The combination of first surface optical thin-film technology and a polished, flat substrate enables this filter to be used with high magnification, a real plus for small planetary nebula." And, finally, this last part - about being "a real plus for small planetary nebula" It just so happens, that I have become very interested in hunting planetary nebula recently; so, I was also happy to read this.
As for me: One of the joys of using this GCE filter - Is that I simply leave a pair of them screwed into the threaded EP barrels of my Garrett signature series 10x50's - And, I just leave them attached all the time. I don't find my views of Asterisms, or Open Clusters darkened very much at all. Yet, they improve the views of all DSO's at same time. I plan to do a side-by-side comparison of these, vs. the pair of Zhumell OIII filters I have, and post my findings.
It would be great, if someone who has other name-brand "Broadband" LPR filters could also do some tests vs. the GCE filter...
The smallest (good-quality) Binoculars I currently have, are my Garrett 10x50's. But, I believe that these would also perform well on smaller Binos - Which would be great when scanning for/observing large, diffuse DSO's. In fact, I believe I just gave myself an idea for a future project...
Clear skies!
-Al
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